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Table of contents
0. Introduction
Brief history
1. The Big Bang ... infinity in the largest and the smallest [Planck size]
2. Elementary particle ... E = mc 2 [gauge theory]
3. Stars ... Cosmic dawn [Cosmic background radiation]
4. Elements ... Alchemy is synthesis of a nucleus [nuclear energy]
5. Black hole ... Birth and death of stars [Horizon of events]
6. Dark matter ... an imperator of gravity [Neutralino]
7. Virgo Supercluster ... Large-scale structure of the Universe [Voids]
8. The history of Milky Way Galaxy ... The formation of the microcosmos [Sagittarius A]
9. The Milky Way Galaxy now ... The structure of the microcosmos [binary stars]
10. Solar system ... Order of the sky [heliosphere]
11. Origin of the Solar system ... accretion disc [gravity]
12. the Earth ... Non-gas components of the solar system [chondrules]
13. Moon ... Giant Impact [tidal force]
14. Crater ... heavy bombardment of the Hadean eon [aerosol]
15. The Sea ... Separation of materials on the Earth's surface [water]
16. Earth's crust ... cooling of the Earth's surface [interface]
17. Life ... Incidence or inevitability [hierarchy]
18. Generation of unit molecules for making life ... The sky, the sea and the sea floor [Frontier molecular orbital theory]
19. The birth of macromolecules for living system … hydrothermal vent on the seafloor [Polymerization]
20. Carbon dioxide assimilation ... Growth of organic matter [Catalyst]
21. Use of energy molecules ... Money of biochemical energy [activation energy]
22. The mechanism of heredity ... RNA World [ribozyme]
23. Place of catalysis ... Maintaining non-equilibrium state [Chain reaction]
24. Birth of a membrane structure ... Separation of inside from outside [Chemiosmotic theory]
25. Protobiont organism was emerged ... Before common ancestry [LUCA]
26. origin of cell ... Life of independence [Molecular fossil]
27. Ribosome ... Mechanism to let genes to function [nanomachine]
28. Craton ... Generation of super cold plume [Convection]
29. Virus ... A key player of evolution [Reverse transcriptase]
30. Genome ... Time engraved in gene [molecular clock]
31. Photosynthesis ... Supply of oxygen and organic molecules [Stromatolite]
32. Banded iron formation ... Reduction of carbon dioxide [Oxidation]
33. Bacteria ... Chaos of the evolution [diversification]
34. The super continent ... the driving force for the evolution of living things [Wilson cycle]
35. Snowball Earth ... faint young sun paradox [Phase transition]
36. Eukaryotic cells ... division of labor and its specialization [symbiosis theory]
37. Reproductive activity ... Men and women [sexuality]
38. Sensors ... To know the outside [receptor]
39. Inconsistency in strata … Lost Records [Precambrian era]
40. Multicellular organisms ... From assembly to organization [Self]
41. Collagen ... wrapping cells [differentiation]
42. Ediacaran era ... The sea in peace [biomat]
43. Cambrian period ... a big explosion of evolution [eyes]
44. Ordovician period ... The Sea of fertility [shells]
45. Silurian period ... advance to the land [soil]
46. Mountain ranges ... collision of Continents [Variscan orogeny movement]
47. Devonian period ... Era of fish [bones]
48. Carboniferous period ... buried carbon [metamorphose]
49. Permian Period ... advanced vertebrates on the land [Amphibians]
50. Evolution of the genome ... Fundamentals of macroevolution [gene duplication]
51. Triassic period ... the largest continent [Pangea]
52. Jurassic period ... Hero of paleontology [Dinosaur]
53. Cretaceous period ... homothermal animals [homeostasis]
54. Gigantic meteorite ... Can we avoid natural catastrophe? [risk]
55. Placenta ... New reproductive strategy [retrotransposon]
56. Cenozoic era ... Animals which educate their children [mirror neurons]
57. Fruits ... co-existence and co-prosperity [seeds]
58. Cenozoic era ... The continents changed currents in the ocean [Antarctic current]
59. Prairie ... Cool climate and short life cycle [C4 plant]
60. The ridge … Disappearance of a lake and evolution of mammals (supernova explosion)
61. Glacial Age ... Earth's cooling down [Messinian salinity crisis]
62. Milankovitch's cycle ... Periodic cooling and warming [Albedo effect]
63. Japan Sea ... Principle on birth of country land [Philippine's Sea plate]
64. Japan archipelago ... Four-way standoff of Plates [Fossa Magna]
65. Primates ... Expert of arboreal life [Oxytocin]
66. Australopithecus ... both humans and monkeys evolved from simians [body image]
67. Hominina ... Genealogy of the ruler [dopamine pathways]
68. Frontal cortex ... Mystery of its amazing development [NOTCH family]
69. Glacial Age ... Fluctuations of rotation and revolution of the Earth [positive feedback]
70. Fire ... the be-all-end-all solution [floresiensis]
71. Neanderthal people ... Brothers of the present human beings [ancient human genome]
72. Modern man ... simultaneous evolution of tool and language [Pinnacle point]
73. Language ... Direct control of vocal organs [FoxP2]
74. First exodus from Africa ... Ancestor with full of frontiers spirit [lice]
75. Second exodus from Africa … Mixed blood with archaic human [Ulm Ice Age]
76. Tools … continuous upgrade of brain function [Microcephalin]
77. Race ... Migration at the global level [adaptive radiation]
78. Wurm glacial period ... the coldest Earth in human history [glacial lake]
79. The continental shelves … submerged history [Sunda land]
80. Oceanic flood ... Human beings lost the paradise [Younger Dryas]
81. Agriculture ... Understanding and application of ecosystems [Indo-European language family]
82. Walled city ... blue eyes [Hypsithermal period]
83. The four great civilizations ... The cooling of the climate produced urban civilization [Pasturage]
84. Code ... the rise and fall of the ancient dynasty [Epic of Gilgamesh]
85. Letters ... Bronze is a nation [Code of Hammurabi]
86. History ... the basis of legitimacy [alphabet]
87. Philosophy ... discovery of individuality [Upanishad]
88. Empire ... Outstanding individuals [Hellenism]
89. Monotheism ... existence behind the Universe [holy book]
90. Map ... Separated by mountains, tied by the sea [compass]
91. The Global Empire ... Connecting the Edges of the Continent [gunpowder]
92. The closure of the country ... An aspect of a mature society [Japanese pirates]
93. The public ... the birth of a democracy [human rights]
94. Japanese people ... Where did we come from [Islands of the Far East]
95. Modern civilization ... Changes in progress in these 2 centuries [science]
96. Industrial Revolution ... Fire confined in iron [Power]
97. Chemistry ... to support high living standards [Molecules]
98. Agriculture ... Hunger destroys civilization [green revolution]
99. Medicine ... Managing the body and hygiene environment [Antibiotics]
100. War ... The Conquest by Europeans [atomic bombs]
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Simple chronology
The biginning of the Universe 13.798±0.037 billion years ago
History of the big bang（after the big bang）
History of the Earth
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It is a good expression to be free from vacillation at 40 years old (Confucius). The questions before in my vacillated days are; What is said solution on the everyday problem, Problems on my specialty life science, their social significance, and difference between common sense and the "short term common sense", how to manage a group, how much emphasis should be given on hierarchical relationship to others, and so on. Recognizing that these problems are actually dependent on limited knowledge of individual, I can see through fog the structure of the society established based on those recognition.
If I arrange and systematize what I am thinking, I could have lived better. I write this text for my own wisdom of life. In order to write as a whole world, I should write about history along the whole-time axis, of which I am aware (the genealogy of the universe, that is, the big history). I should choose points to consider from the history to summarize various ideas (the genealogy of ten thousands of theories). I tried to keep the expression in everyday language. Would not it be ambiguous to make special words to express sophisticated thought? Will not you fall into a word game? I thought to express sophisticated thought by everyday written language.
Currently there is a convenient means of presentation such as the Internet. However, only when I put long story on a web page, it is hard to read, and is not to be read. Besides, considering from my own past experience, it will become troublesome for me to write it and probably, I will quit writing it. Therefore, I thought that it would be better to use an e-mail magazine. Every week, starting from the birth of the universe to modern themes, I will explain the history of the Earth, life, and mankind from view point of contemporary perspectives. I emphasize the way of thinking, particularly from a scientific view, and write on the theme of understanding of human life. Proceed to the next even if it is not completed, and write a revised version after it has been completed. If I build up the history in repetitive way, I will be able to check my philosophy and the underlying knowledge as a whole. I can reconfirm my knowledge on the Internet. I feel that the world will spread when I find various information and ways of thinking from the related webpage in the network.
We all have large amounts of non-classified knowledge, and we always want to make them systematic. In school days, textbooks would have been a system of knowledge. When becoming a social worker, knowledge gained in daily life is fragmented, such as activities in the workplace, family and community, and professional knowledge on work, personal knowledge reading and hobbies. When fragments of knowledge are connected with unexpected links, or when I notice conceptual similarities between the fragments, my cross-contextual system of knowledge will expand slightly. I feel pleasure at such works. These are the metacognitive or transferable skills.
Over the course of several versions, I began to think that it was assembled into new "myth = creation of the world". The hobby that I enjoy using e-mail magazines is, to make it a big history, the same as creation the world by utilizing the knowledge accumulated through science. As in the doctrine and philosophy of the former religion, this new "myth" needs to overlap as much as possible with every life, and it will be a tool to enrich the life and society as a whole.
Since this is work for myself only, I have an image like assembling a block puzzle according to the depth of my own recognition, to the extent that I knows. I will quote Mr. Kenzaburo Ohe, Japanese writer with Novel prize. "What I remember incorrectly was much worse than not being memorized was that my father told me, and I respected those who can incorporate in a daily conversation what they remembered from the book, as it is also interesting." (in “To the new people")
Unfortunately, there are some historical blanks in human knowledge. That part was filled with my hypothesis that seems plausible for me. I chose the hypothesis backing my confidence that I have solidified the philosophy of science. It is a statement that I want to continuously explain the history of the universe with a reasonable hypothesis. This volume does not investigate into the general theory, nor does it introduce a unique view that is different from the traditional one. It is just a compilation of the efforts of the wonderful people introduced in the literature at the end of this volume.
About 13.8 billion years ago from now the Universe was born from a fluctuation of vacuum.
The Big Bang theory predicts a singular point in the beginning of the Universe. The size of the Universe at singular point is Planck size (10 -44 seconds, 10 -33 cm)). In Planck size, the energy conservation law and Einstein's theory of relativity, and so on, are broken due to Heisenberg's uncertainty principle. In this size, substances are generating and/or disappearing in vacuum (virtual particles).
Immediately after birth, the Universe rapidly expanded due to inflation by 10 -34 seconds, and it became overcooled. The universe became extreme dense at high temperature with the energy released when the vacuum transformed from an unknown state to the Universe of the present state. As inflation happened, the early Universe escaped from black hole formation by self-gravity. A vacuum has potential energy and tends to settle from a high energy state to a low state. The Universe born from the vacuum can lower the potential energy by the inflation.
The Universe which rapidly expanded by inflation extended the initial small fluctuation as it was. Currently, the fluctuation manifests itself in a slight non-uniformity of cosmic background radiation and unevenness in the distribution of galaxies. Small fluctuations were magnified by gravity, forming a large-scale structure of the Universe. The artificial satellite named Planck for observation of the cosmic background radiation was launched in 2009 and the data were opened in 2013. The composition of the Universe was 4.9% for baryon, 26.8% for dark matter and 68.3% for dark energy. The Hubble constant was 67.15 ± 1.2 km/sec/Mpc, and the age of the Universe was 137.98 ± 0.37 billion years.
Galaxies are making groups on a scale of about 10 million light years. Galaxy groups and galaxy clusters (larger than group) further form a supercluster. The Milky Way Galaxy which our solar system resides belongs to the Virgo supercluster. Galaxy supercluster has size of several hundred million light years. In the Universe there is a large space where there is no galaxy. Examining the distribution of the galaxy, it turned out to be a foamy structure, and the galaxy turned out to be gathering around bubbles (space without galaxies. so called Void).
Sum of gravity of visible stellar matters is not sufficient to produce the large-scale structure of the Universe. A theoretical calculation shows it takes too much time to form it. Assuming a dark matter with mass of several times larger than one of visible materials, a hypothesis was born that stars and galaxies were formed around dark matter through attracting interstellar gases and stars. The dark matter is indirectly measured its mass and distribution using the gravitational lens effect. When you look at the map showing the large-scale distribution of dark matter in the Universe, you can find the network structure of the dark matter grows with the passage of time (as it approaches the Earth), and it seems to be separated by a huge void. The galaxy formation was demonstrated visually that the galaxies concentrate along the network structure of the dark matter and the galaxies grew in the dark matter.
After inflation, it is reasonable that expansion of outer space has advanced at a constant speed. Recently, it was observed that the far supernova flied away at a speed higher than the speed when considering the expansion rate of the Universe is constant. That is, the expansion of the Universe is accelerating. Therefore, we are newly introducing and explaining the concept of dark energy. Before 13.8 billion light years, space expands at a speed exceeding the speed of light, so it is called the horizon of the Universe. The current universe calculated from the speed of expansion is a radius of 47 billion light-years. The outermost side of the space is an account which is far away at more than three times the speed of light.
It is thought that force (interaction) was born at the same time of the birth of elementary particles. Gravity first emerged from the unified field. It is estimated to be 10 exp (-38) seconds after the universe was born. Since other interactions are transmitted by exchange of elementary particles such as photons or gluons, the putative particle that transmits gravity is called graviton. As gravitational force (universal gravitation) acts all elementary particles, and works to infinity without being interrupted, so it dominates in the stellar world. Gravitational force is responsible for navigation of the celestial bodies such as the Earth, the Sun, the galaxy, and it creates a structure in the huge Universe.
Space inflation began immediately after the birth of gravity, and was completed at 10 -34 seconds after the Universe was born. Then, at 10 -33 seconds, the strong interaction mediated by gluon and the electroweak interaction (weak interaction and electromagnetic force) appeared. Quarks, leptons (6 species. among them, the electron and the neutrino are stable) and the gluons were in a state of free motion in the Universe at a very high temperature. The plasma of quark and gluon showed behaviors like gas or liquid. At that time, the weight of a mass like a tip of pin was as heavy as that of the Egyptian pyramid, and the temperature reached one million times of the center core of the Sun.
At 10 -13 seconds after the universe was born, along with the cooling of the Universe, the electroweak interaction was divided into weak interaction and electromagnetic force. The weak interaction can transmit very short distance, so we cannot observe their impact in the everyday world. Almost at the same time, at 10 -13 seconds thereafter the vacuum was filled with Higgs particles (Higgs' sea, or Higgs field), masses were created in elementary particles (other than photons) interacting with Higgs particles. Quarks and leptons reacted with the Higgs field. When flying in space, they received brakes by the Higgs field, the speed became lower than the speed of light. Also, when accelerating or changing the direction of particle motion, certain external force needs to be exerted.
Unlike kinetic energy, static mass energy does not decrease even if the Universe expands. Therefore, the energy density of matter decreases by the amount of increase in volume due to the expansion of the Universe, but it decreases slowly compared to the energy density of light. As a result, as the Universe expands, the energy density of matter increases compared to that of light. By the time protons and neutrons were born (10 -6 seconds after the birth of the universe), the energy density of matter was only one billionth of that of light.
A state filled with light, that is, what is called a photon gas, has a high pressure. When the density increases in a certain region, it tries to return to the original density by the repulsion due to the correspondingly increased pressure. Therefore, during the energy density of light is higher, the density fluctuation cannot grow no matter how hard the gravity works.
At 10 -6 seconds after the birth, the quark joined by gluon, protons and neutrons (complex of three quarks) and mesons (pair of two quarks) were born. Protons and neutrons formed atomic nuclei via mesons. The elementary particles responsible for strong interactions, gluon, are trapped in protons, neutrons, and nuclei, and from then on, none can see them in the everyday world. As the temperature further declined, protons and neutrons, their associated nuclei, electrons, photons, and neutrinos were left as basic particles in the Universe at 10 -4 seconds after the birth. At that time, the Universe was filled with dark matter in addition to the elementary particles. The number of nuclei produced was 1 per 1 billion photons.
One minute after the Universe was born, the deuterium atomic nucleus, in which a proton and a neutron are coupled, were stabilized. Then nuclear fusion advanced and light nuclei were synthesized. In the early Universe, almost atomic nuclei were consisted one proton, that is hydrogen (or deuterium, if a large number of neutrons were created) or two protons (helium nuclei).
Neutrons, protons, and electrons combined with photons to form a liquid plasma state, and fluctuations of small density became waves (baryon acoustic oscillations) that filled the Universe. At first, the ratio of protons and neutrons was 1:1, but the neutrons are so unstable to decompose into protons and electrons. This decomposition sharply decreased after 3 minutes post Big Bang, because nuclei started to be formed. At this time, the number of protons became seven times the number of neutrons.
Three minutes after the Big Bang, nuclei of hydrogen and helium were formed. There are three kinds of nuclei of hydrogen including one proton and 0, 1, or 2 neutrons. In addition, atomic nuclei of helium are two kinds including 2 protons and 1 or 2 neutrons. The universe was filled with nuclei and free electrons, which was still plasma state. Furthermore, very few lithium and beryllium nuclei were born in 1000 seconds after the Big Bang.
The energy density of photons drops sharply with the expansion of the Universe. It was 50,000 years after the birth of the Universe that the energy density of photons finally became less than the static mass energy densities of ordinary matter and dark matter. If main source of the energy density of the Universe changed from light to matter, the speed that the Universe expands would also change. There is no change in the gradual deceleration of the expansion rate, but the degree of deceleration became smaller because the decrease in the energy density of the substance was slower than that of light. At the same time, the reversal of the energy densities of matter and light begins to amplify the density fluctuations of the Universe, which is the driving force for the formation of stars and galaxies. The density distribution of matter was generated as a superposition of waves by baryon acoustic oscillations.
When the temperature of the Universe cooled to about 4000 K (K is absolute temperature) after about 380,000 years after the Big Bang, electrons were captured around the nucleus by electromagnetic force, then atoms were formed. This phenomenon is called neutralization of the Universe. Then, the light, which could not go straight by absorbed or released by free electrons, could go unimpeded. Thus, the Universe became transparent (clarification of the Universe). The light filling the Universe at this time is observed as 2.7 K of cosmic background radiation today. The size of the Universe at that time is estimated to be 1/1000 of the present.
Starting with the density fluctuations created by inflation as the initial conditions, the smaller scale fluctuations grew first. Therefore, a small halo was able to be created first, and then it repeatedly coalesced to grow into a larger halo. Eventually, galaxy-scale halos appeared, leading to large-scale structures of galaxy clusters and the universe. And stars are born in the dark matter halo. It is also the birth of a galaxy.
Many first-generation stars appeared to be born 50 million years after the Big Bang. The first generation stars are mostly made of hydrogen, and are larger and hotter than stars that contain heavy elements such as the Sun and emit more photons. In 180 million years after the Big Bang, hydrogen atoms were heated by stellar light, and ionization of the hydrogen atoms began. The first generation stars had a short life span due to its large mass, and supernova explosions frequently occurred.
The story by the simulation is as follows. Small primitive stars of about 1% of the solar mass were formed 300 million years after the Big Bang. The primitive stars gathered the gas around, grew and began to shine strongly when it was about 20 times of the solar mass. Their growth was suppressed by light pressure, and growth stopped at about 40 times the solar mass. Another simulation predicts a huge star that will reach 100 times the solar mass.
Hydrogen left in the space ionized by ultraviolet rays from the stars. This process after about 500 million years from the Big Bang is called re-ionization of the Universe. The oldest (furthest) galaxy that can be observed now is a quasar of about 600 million years after the Big Bang (13.2 billion light years ahead). Eventually, as galaxies were formed, the number of hydrogen atoms decreased from outer space, reaching the current concentration level in 940 million years after the Big Bang. This is called the dawn of the Universe.
The lifetime of a star is called evolution. The mass of the first generation stars that were first born in the Universe are orders of magnitude larger than those of the present age, because the Universe was so small that the high concentrations of hydrogen and helium were available as materials. Hydrogen gas flocculated due to gravity. When the central part of the gas exceeded 10 million degrees, nuclear fusion reaction started.
In the early Universe, the ratio of number of hydrogen with a proton to deuterium containing neutron was estimated to 6:1. Deuterium is generated from two hydrogen nuclei (protons). When two protons collide, one emits a positron and a neutrino and turns into a neutron (Beta plus collapse). Positron annihilates with surrounding an electron and turns into gamma rays. Thus, a deuterium nucleus is formed composed of a proton and a neutron. When a proton, a hydrogen nucleus, is bonded to a deuterium nucleus, a helium 3 nucleus (two protons and one neutron) is formed. Two helium 3 nuclei react with each other to form a helium 4 nucleus (two protons and two neutrons) and two hydrogen nuclei (one proton each).
The helium nucleus accumulated in the core of the first generation star as an ash of the nuclear fusion reaction, and outside the core, hydrogen nuclei continued fusion reaction. Eventually, as hydrogen nuclei become less and nuclear fusion reaction becomes weaker, the temperature dropped. As the temperature decreased, the central core shrank due to gravity, and its temperature and pressure rose. Then helium nuclei began nuclear fusion reaction. Three helium nuclei turned into one carbon nucleus (6 protons). Furthermore, oxygen nucleus (protons 8) was formed from a carbon nucleus and a helium nucleus. Subsequently, carbon underwent a nuclear fusion reaction.
Nuclei such as neon (10 protons), sodium (11 protons), magnesium (12 protons), etc. were formed a nuclear fusion from 2 carbon nuclei. Further nuclear fusion reactions produced silicon (14 protons), Iron (26 protons), and so on.
When the main nuclear fusion reaction ends inside the star, heat was no longer generated, the core of the star shrinks. Then the temperature and pressure of the core rise to start the next nuclear fusion reaction of heavier nuclei. The temperature and pressure of inside of the star gradually become high. As heavier nucleus accumulates in the core, the core of the old star has several layers of nuclei. In the core of large and old star, iron nuclei were accumulated.
As the atomic number increases, nuclear fusion reactions are less likely to occur because the Coulomb repulsion between the nuclei (the force that particles with the same charge repel each other, the nucleus has the positive charge of the proton) becomes large. The heaviest element that can be generated in the nuclear fusion reaction is iron, having an atomic number of 26. That is, nuclei lighter than iron were produced inside the first generation stars.
After the Universe was born, in the hundreds of millions of years, the first generation stars got a supernova explosion and became black holes. The energy of the supernova explosion released relatively light nuclei produced by nuclear fusion reaction into outer space. In addition, heat and pressure of explosion created a heavier nucleus than iron.
The gas temperature dropped when the first-generation star exploded and the heavy nuclei were scattered into the space. The relatively cold gas clouds were broken apart and each became a star. Since then, no huge star nor black hole like the first generation star were not formed. Black holes are formed by gravity collapse when a relatively large star explodes as supernova. The mass is at most 10 times the solar mass.
If only hydrogen and helium are component, the temperature of the gas rises so high during the formation, and only very massive cloud can become a star. First generation stars are considered to be 100-1000 times the mass of the sun. When the iron core of the first-generation massive star reached to temperature of 5 to 10 billion K, the energy of the emitted light reaches the level of energy connecting neutrons and protons in a nucleus. This high energy light caused nuclear fission. The iron nucleus decomposes into helium nuclei and neutrons, which is an endothermic reaction. As the temperature decreases, the pressure maintaining the core mass sharply drops and the outer layer of the star fall toward the center. The nuclear fusion reaction accelerates at once, the outer layer of the star blows off, and a supernova explosion occurs.
In the case of large-mass stars, under extremely high pressure, an electron is absorbed by a proton and becomes neutron, so the staller core becomes to contain only neutrons. This is called a neutron star. If the mass is larger, the extremely high gravity presses a neutron, and the core falls inside due to strong gravity. This is called gravitational collapse, and the core condenses into a black hole.
The first generation supernova explosion blew out the surrounding gas, (gravity wave) compressed the interstellar gas and created a number of second generation stars. Stars of the second generation have a long lifetime because the mass is small compared to the first generation. The second generation stars are currently observed in clusters around the galaxy as a star with poor metal element. When a massive star among the second generation reached the end of a supernova explosion, a large number of heavy nuclei were supplied to the universe. The stellar made after this contains a relatively large number of metallic elements and is called a third generation star. The Sun is the third generation. The galaxies of 10 billion years ago has been confirmed that their interstellar gas contain very low heavy elements. In the galaxies of the same age, it is also observed only small number of galaxies storing large amounts of dust and heavy elements.
Even trace amounts of heavy elements have a great influence on the formation and structure of stars. Heavy elements emit more infrared rays than hydrogen and helium. When heavy elements are included, even a smaller amount of gas can be contracted into the stars. Heavy element acts as a coolant when stars are formed and suppresses expansion due to heat. From the second generation onwards, stars of relatively smaller weight have come to be born.
In the process of making a star from a gas cloud of about 100 times the mass of the sun, when the mass of the center star reaches 20 times the solar mass, the pressure of light prevents the sedimentation of the gas to increase the weight of the star no more. However, in reality there are gigantic stars. When the light pressure and the gas settling press together, Rayleigh-Taylor instability occurs with a slight fluctuation, and the gas settlings fall into a star as a mass. According to the simulation, from a gas cloud about 100 times the mass of the sun, two stars of 30 times and 40 times the solar mass were born. In the universe there are many binary stars because there were many gas clouds of large mass.
In supernova explosion, a large number of neutrons are generated. Neutron has no charge. Coulomb repulsive force does not work so that neutrons are easily absorbed with the surrounding nuclei. A nucleus containing more neutrons than usual becomes unstable, so an excess neutron releases electron and gamma ray to become a proton, hence increases the atomic number by one. With this repetition, a large number of heavy nuclei more than iron were created in a short time. The follows are a summary of generation of elements.
In the center of a large galaxy in the Universe, there is a black hole with a mass between 1 million and 1 billion times of the solar mass. The black hole at the center of the galaxy is thought to have been formed by the gravitational collapse of a huge gas cloud during 1 billion years after the Big Bang. An ancient massive black hole is observed as a quasar. A quasar is a celestial body where powerful electromagnetic waves are generated due to a large amount of substances falling into a huge black hole. Iron was found from the spectroscopic observation of a quasar.
In the early universe, which is only 2 billion years after the Big Bang, we can find many massive gas bodies with masses that are almost the same as galaxies. Giant gas bodies create numerous stars and would condense into galaxies. Recent observations in the young universe of 4 billion years after the Big Bang suggest that star formation activity was at its peak in large mass galaxies. Stars were born there with an unexpectedly high formation rate.
The first galaxy was formed 300 million years after the Big Bang. The density fluctuation of the dark matter at a level of about one over hundred thousandth that existed in the early universe grew under its influence of gravity and gathered baryons, forming celestial bodies of various sizes everywhere. A galaxy with many stars and interstellar matter was born in the space where massive substances were gathered. The dark matter surrounding the galaxy is spherical. Galaxies formed in the dark matter turned into a disk shape by rotation.
In the universe up to two billion years after birth, glowing lumps of hydrogen gas of galaxy size are observed. They are called Lyman-alpha blobs (LABs). Having a black hole in the center, it looks shiny by the substance falling into the black hole. The size of LABs is almost the same size of the current galaxy. It is thought that LABs evolved into galaxies. Unless LABs are assumed for the evolution of the Universe, the size of the modern galaxy would be enormous in size. It is thought that the formation of the second generation star in LABs was completed by from 3 to 4 billion years after the Universe was born.
The star formation rate of the galaxy is correlated to the total mass of the material which makes the star. From the beginning of the universe to the present, the star formation rate has gradually decreased. Even in early galaxies of the Universe, the star formation rate increased with the mass of the galaxy, and its efficiency was more than 20 times higher than it is now. The black hole located in the center of the galaxy is called blazar. Study examining the gamma-ray attenuation from blazars in the range of 200 million light years to 11.6 billion light years shows that the gamma ray was the weakest between 9.7 and 10.7 billion light years, indicating that many stars were born in this time period. The amount is 10 times of the current. In other words, after the Big Bang, there was a peak of star birth 3 to 4 billion years later.
The mass of the black hole at the center of the galaxy, including medium-sized black holes, correlates with the size of the galaxy. Therefore, scenarios are predictable where black holes grow by merging with galaxies and absorbing surrounding stars. The Dark matter apparently influenced to this process.
The results of an international project to observe the distance and recession of distant galaxies using Type Ia supernovae in the 1990s have revealed that the Universe has been expanding since its birth. Initially, the expansion rate is gradually slowing down. The gravitational force of the mass of the Universe braked the expansion of the space, resulting in deceleration expansion. However, from 7 billion years ago, the universe changed from decelerating expansion to accelerating expansion. Dark energy is supposed to be the source of the accelerating energy.
The mass distribution in the present Universe has a bubble-like structure, reflecting the fluctuation of density in the early Universe. That is, galaxies are found gathering around a huge space (void) where no galaxy exists. The collective state of galaxies is named as a galaxy group, a cluster of galaxies, or a supercluster.
The galaxy group to which the Milky Way galaxy belongs, to which the solar system belongs, is called the Local Group of Galaxy. In the Local Group of Galaxy, the largest galaxy is the Andromeda galaxy, and the heaviest galaxy is the Milky Way galaxy. There are many companion galaxies are bound by their gravity around both galaxies. It contains about 50 dwarf galaxies in the range of 10 million light-years.
One of the groups of galaxies that are closest to the Local Group of Galaxy is the Sculpture Room Group of Galaxy and the Maffei Group of Galaxy, which are separated by 7-10 million light-years. In addition, the Ursa Major M81 Group of galaxy, M101 Group of Galaxy, Aquarius M51 Group of Galaxy, Centaur A / M83 Group of Galaxy.
There is a Virgo galaxy cluster about 50 million-70 million light years away, all of which are included in the Virgo super galaxy cluster. The Virgo Cluster contains 1300 to 2000 galaxies, 15 million light-years across, and has a huge elliptical galaxy called the M87 galaxy in the center. The supermassive black hole in the center of the M87 galaxy was photographed in 2019. All of these are included in the Virgo Supercluster.
Although some astronomers think that the Local Group of Galaxy is being taken into Virgo Galaxy Group, there is a negative opinion because the expansion of the universe is accelerated by the dark energy. Recently, a huge attractor has been discovered that is attracting the surrounding galaxies about 200 million light years. It is proposed as La Keania superclusters, including the Virgo cluster and local galaxies.
A huge hole was discovered in the Ophiuchus cluster of galaxies, 390 million light-years from the Earth. It is estimated to be 15 times larger in diameter than the Milky Way. It is assumed as the trace of a huge explosion. The Ophiuchus cluster of galaxies is consisting of thousands of galaxies. At the center of the Ophiuchus cluster, there is a galaxy with a huge black hole with a mass of 10 million times of the Sun. It is hypothesized that a jet emitted vertically from the black hole intensified for unknown reason and blew away the galaxy beyond it. Not only the density fluctuations of the early Universe but also other factors were possibly involved in the formation of the large-scale structure of the Universe.
Assuming the maximum estimate of total mass of the dark matter, it cannot fill up the gap speed difference between speed of the clustering of galaxies and the expansions of the Universe. Therefore, according to the expansion of the Universe, the space between each cluster of galaxies and super galaxies increases. Ultimately, it is predicted that individual clusters of galaxies are blocked by the wall of light velocity (separation speed exceeds light speed) and separated as an isolated universe (space).
Regarding the appearance of the Universe in the distant future, the conclusion whether it will be a small universe by a cluster of galaxies, that is, a universe that will continue to expand forever, or a big crunch will be depended in the Grand Unified Theory which we have to wait for theoretical analysis.
A large amount of hydrogen gas equivalent to the weight of a galaxy was collected in the gravity well formed by Black Matter, and star formation began. It was a billion years after the Big Bang. The giant star formed in the center of the gravity well burned out in about 10 million years, causing a supernova explosion and scattering a large number of heavy nuclei and its own debris around it. A huge black hole was left in the center. In the early Milky Way galaxy (still a mass of hydrogen gas), several more first-generation stars exploded into black holes here and there with supernova explosions.
Supernova explosions promoted the birth of stars. When a large-mass star is born in the center of a huge molecular cloud, the light exerts pressure on or ionizes the surrounding molecular cloud to create a high-concentration molecular cloud. Molecular clouds condense into stars, and light reaches farther. By repeating this process, a characteristic OB association was formed. In the early days of the Milky Way galaxy formation, it seems that there were hundreds of structures, in which thousands of stars were strongly connected by gravity, such as small satellite galaxies and globular clusters. One of them is the globular cluster Palomar 5, which is 20,000 parsecs away from the Earth. The age was estimated to be 11.5 billion years. The growth of the Milky Way galaxy was at its peak 3 billion years after the Big Bang (11 billion years ago). This corresponds to the time when a large number of stars were born in the Universe.
Second-generation stars contained a large amount of heavy elements, so they were able to dissipate their heat efficiently, be formed neatly, and shine longer. Second-generation stars exploded one after another 2 to 6 billion years after the Big Bang (12 to 8 billion years ago), increasing the amount of heavy atoms in the Universe. Substances that do not emit light by themselves are classified into diffused nebulae, planetary nebulae, dark nebulae, etc. depending on how they look. They are mainly gas and dust. It is called interstellar gas when it has a density 100 times higher than that of normal outer space. Eventually, it is compressed by its own gravity and nuclear fusion begins, and a star is born. In this way, the stars moved to the third generation.
The Milky Way galaxy was formed by attracting stars around Sagittarius A, the first supermassive black hole. During 13 billion years of its history of the Milky Way galaxy, at least half a dozen incidents that it swallowed small satellite galaxies and globular clusters. The smaller galaxies born in the Milky Way Dark Matter were absorbed by the Milky Way Galaxy one after another. One of them was the dwarf galaxy Enceladus, which was estimated to have been absorbed 10 billion years ago. The size of Enceladus is thought to be about the same as the Large Magellanic Cloud, which is the current satellite galaxy. Every time the Milky Way galaxy swallowed the smaller galaxy, intense star formation occurred.
The Milky Way galaxy rotated around the Sagittarius A giant black hole and gradually flattened. Also, a swirl pattern was formed. The spiral pattern of the galaxy is a compressional wave of stars. It happens that gravitational pockets are formed in high density places and it takes time for stars to pass there. In other words, because the stars were rotating motion and accumulated, they became an arm structure. In addition, the interstellar gas also gathered and became a place where stars can be born.
The Milky Way Galaxy is a group of celestrial bodies to which our solar system belongs. Twenty small galaxies (dwarf galaxies) such as the Magellanic Cloud are moving around the Milky Way galaxy, bound by the gravity of the galaxy. The dwarf galaxies are distributed around the Milky Way galaxy within a radius of about 400,000 light-years. A microcosm containing globular clusters, open clusters and other groups of stars and interstellar medium. Most of the stars are in the disk of 100,000 light-years in diameter, and stars in the bulge are older than those in the spiral arm.
At the center of the Milky Way Galaxy, there is a strong radio source, a huge black hole called "Sagittarius A". Since the interstellar matter is concentrated at high density around it, it cannot be seen optically. Observations were made to track the movement of the star existing near the center of the Milky Way Galaxy from the 1990s for more than 10 years. Analysis of the trajectories by the universal law of gravitation revealed that the mass of the giant black hole at the center of the Milky Way Galaxy is 3.7 million times that of the Sun. The diameter is 0.15 astronomical units (22.5 million km).
There is a region called a halo that spherically surrounds the Milky Way galaxy outside the disk part. The radius of the dark matter halo is about 300,000 light-years, accounting for 90% of the total mass of the galaxy. The oldest celestial bodies among the stars forming the Milky Way galaxy are globular clusters scattered in this area. These stars are second-generation stars that contain heavy elements such as iron only about a few hundredths of the Sun. The 11.7 magnitude star of the Cetus has only one-eighth of the Sun's abundance ratio, but it was unusual to detect thorium 232 and uranium 238 of radioactive atoms. Based on their relative abundance ratios etc., its age was determined to be 12.5 billion ± 3.3 billion years. This value is considered to correspond to the age of the Milky Way Galaxy.
The disks are occupied by dark nebulae and stars belonging to population I (third generation) such as main-sequence stars and cepheus type variable stars. The red dwarfs are expected to be the most abundant stars to form the galaxies. Their size is less than 1/3 of the diameter of the Sun, the surface temperature is a dark star of about 3500 degrees. The fusion rate of hydrogen is slow, and the lifetime is very long. There is nothing visible to the naked eye. 348 celestial bodies within 10 parsecs (33 light years) from the Sun were examined, of which 239 (about 69 percent) were red dwarfs. Also, half of the stars are binary stars.
The solar system lies in the plane of the Milky Way Galaxy and is on the galaxy center side of the Orion arm, which is sandwiched between the Sagittarius arm and the Perseus arm. It locates 26 thousand light years from the center of the galaxy. The 6 million stars around the Sun are distributed in a snail-like spiral. The age of the Sun is calculated to be 4.6 billion years from the measurement of the collapse of uranium 238. That is, 9.1 billion years after the universe was born, 7.9 billion years after the Milky Way Galaxy was born. The intrinsic velocity of the sun is 220 km/s. The sun goes round the center of the Milky Way Galaxy once in 200 million years. It is estimated 23 laps already.
The sun is in the middle of a local bubble about 300 light-years in diameter. A thick layer of interplanetary dust is formed around the local bubble, and the interplanetary dust is thinner in the local bubble than the surrounding area. The local bubble is filled with plasma, which has a higher temperature than the surroundings. Furthermore, seven stellar groups are formed on the surface of the cavity, and all the stars are about several million years old. From the motion of the stellar groups, it was predicted that the local bubble was formed by 15 supernovae exploding in 4 times with about every 4 million years interval, from 14 million years ago. It was calculated that the Sun was about 1000 light-years away at the beginning and entered the local bubble 5 million years ago. The Sun will break out of the local bubble in 8 million years.
The elements existing in the solar system are, in increasing order, hydrogen, helium, oxygen, carbon, nitrogen, iron, magnesium, sulfur, aluminum, sodium, calcium, nickel. Most of the substance (mass) is in the Sun. These elements are the nuclei formed by the nuclear fusion reaction inside the stars. Many kinds of heavy atoms produced by supernova explosion or merger of neutron stars were also included.
The main celestial bodies of the solar system consist of the single star, the Sun, eight planets, and satellites orbiting the planets. Planetesimals that could not grow into large planets between Mars and Jupiter remained as asteroids and became an asteroid belt. Just under 120,000 asteroids have been discovered, for example, Ceres, Pallas, Juno and Vesta. The asteroid Vesta has a layered inner structure like the Earth.
Only some planetesimals grew selectively and became protoplanets. They grew and grew by collecting a lot of small planetesimals remaining in the surroundings. When the activity of the Sun rose, solar wind was generated. The wind blew the gas out of the area close to the Sun. At last, the protoplanets collected all surrounding planetesimals. The planets ceased to grow and were born with hard ground like the earth.
On the outside of Neptune, there are many celestial bodies without gas, called Edgeworth/Kuiper belt. The origin of a short cycle comet is here with a cycle of 200 years or less. These objects are collectively referred to as dwarf planets. Pluto, which was classified as planet before, became to be regarded as a dwarf planet.
The Sun releases supersonic plasma called solar wind in every direction, and it creates a huge spheroid cavity in the interstellar gas. This cavity is called the heliosphere and spreads over about 100 to 150 astronomical units (AU) (1 AU is the average distance from the earth to the sun, about 150 million km). The supersonic solar wind decreases rapidly at the surface of termination shock, and then equilibrated at the surface called the heliopause. Outside the terminal shock wave surface, the solar wind flows at low speed and is called Helio Sheath. In this area, the interaction between the solar plasma and the interstellar gas becomes dominant.
In the 2000s, growing star systems were discovered one after another by observations with the ALMA radio telescope. Various primitive stellar disks were discovered. It was found that the beautiful planetary system like the solar system is exceptional and there are various planetary orders.
By examining the age of the meteorite, it is calculated that the solar system was born 4.6 billion years ago. There is a theory that the birth of the solar system was triggered by a starburst that occurred when a dwarf galaxy collided with the galaxy 4,567 million years ago.
Clouds of interstellar matter that became the solar system was gradually condensed and falling into the center of gravity. Most of the gas was such as hydrogen molecules and carbon monoxide molecules. Although the ratio to the total mass was small, there was also a large amount of minute solid particles of about several micrometers. The gas swirled because the angular momentum was preserved while falling and condensing. When agglomerating due to gravity, gravity and centrifugal force antagonize in a plane perpendicular to the rotation axis of the disc, and the material does not immediately fall to the center. On the other hand, since the centrifugal force does not act in the direction parallel to the rotation axis of the disc, aggregation by gravity proceeds. As a result, the material distribution gradually flattened and a rotating accretion disc was formed.
Then a giant gas ball was made at the center of the rotating accretion disc. The core of the gas ball was compressed and its temperature rose. When its temperature exceeds the critical, nuclear fusion of the hydrogen nucleus started and became the primitive Sun.
In the primordial solar system, it is estimated to be 10 to 100 million years from the time when molecular clouds begin to shrink to the time when the solar system is formed. The dust materials in the accretion disc gathered slowly, making small lumps due to adhesion and inelastic collisions. The small lumps are called pebbles. These pebbles became a planetesimal with a diameter of roughly 10 km. The planetesimals grew while revolving around the Sun, striking each other, stuck together, being broken by the impact of the collision. Some planetesimals had a core of metallic iron. From the accretion disc to the formation of a planetesimals with a diameter of about 10 km was quite quick, estimated to be around 100,000 years. The planetesimals were assembled over the 30-40 million years to form the Earth.
When the mass of the protoplanet exceeds about 10 times the mass of the Earth, the planet can effectively collect hydrogen gas by gravity. Because of the mass of gas component was as many as 100 times that of the solid component in the protoplanetary disk, the mass of such a big planet rapidly increased. Jupiter type planets which had a mass of 10 times of the Earth mass were formed, wearing gas of many times the mass of the core around the nucleus (core). Jupiter was short of weight to switch on nuclear fusion. Similar gaseous gigantic planets were born outer than Jupiter, named Saturn, Uranus, and Neptune. Metallic elements are fewer at the outer side of the solar system, and are considered to be composed of light elements such as ice and dirt.
On the outside of the solar system, the planet formation like the early solar system still proceeds slowly. As the primitive molecular clouds evaporated, these objects appear to have been left behind on planet formation. Eight planets are known in the solar system. There is a theory that there is a ninth planet from the orbit of the dwarf planet outside of Neptune, which is about 5-10 times the mass of the Earth.
The rocks on the Kuiper belt are disturbed by the gravity of Neptune and others, and become comets. By the same mechanism, rocks and celestial bodies are injected from the Kuiper belt into the asteroid belt inside Jupiter's orbit. Kuiper belt objects approaching the Sun lose their volatile components by heat, turning them into ordinary rocky meteorites. In addition, the fall of this rock to the gravity well of the Sun is still ongoing.
The Earth that had orbited around 150 million kilometers from the primitive Sun has a different appearance from other planets.
Constituents of the primitive Earth are estimated by investigating planetesimals that are not absorbed by the planet, drifting in the current solar system. Specifically, they are a meteorite and a comet. Among the meteorites, the oldest one is carbonaceous chondrites that existed since the planet was formed. The chemical composition of this meteorite is the same as that of the solar system except for hydrogen and helium. Besides iron and nickel, it contains a considerable amount of water and hydrocarbons. It includes small spherical particles called chondrule, which is said to have formed 4.56 billion years ago. In the state of zero gravity, volatile molecules will assemble to become spheres. Carbonaceous chondrites are thought to be meteorites that are not subjected to thermal transformation such as melting and solidification.
In the current solar system, the long tail of a comet will additionally contain water vapor around the Earth's orbit. However, at the time when the Earth was born, the energy radiation from the Sun was less than present. The temperature around the Earth's orbit is much lower, and the planet may have contained a lot of ice and organic matter of low molecular weight. The surface of the ancient Earth may have been a mud containing a large amount of simple carbon compounds rather than rocks.
The protoplanet grew by attracting many remaining pebble and planetesimals around it. When the activity of the sun became active, a solar wind was generated, blowing gas from the area near the sun. In about a million years, a slight difference in size grew into more than a dozen primitive Earths. At that time, Jupiter finally grew, affecting the orbit of the proto-Earth and pushing the proto-Earth group to the final growth.
The planetesimals falling to the Earth melt due to collision energy, and water and gaseous components contained in them evaporated rapidly. When the Earth became about half the size of the present, gravity reached a strength not to let gas escape, and a layer of the atmosphere was formed. Furthermore, volatile substances were supplied to the Earth from the meteorites fallen to the Earth. The atmosphere and the sea were born 4.37 billion to 4.2 billion years ago. The greenhouse effect of the primitive atmosphere slowed the rate at which heat escapes to outer space. The surface of the Earth gradually turned into magma. Eventually, the surface changed to a boiling magma ocean, its depth reached 500 km, and its temperature reached over 1,000 degrees Celsius. In the magma ocean, heavy iron and other heavy components separated from light rocks and accumulated at the bottom of the magma ocean. However, there are negative opinions on the existence of the Earth's atmosphere before the giant impact.
When the Earth reached to a size with radius of about 70% of the current, the heavy metal accumulated at the bottom of the magma ocean fell to the center at once and made a nucleus. At the same time, the gravity energy released from heavy metal melt the Earth completely. The light rock components, which were the equivalent with magma ocean, were separated from the metal nucleus.
If most of the heavy metals such as iron sink as nuclei, the elements left on the surface of the Earth were oxygen, carbon, nitrogen, silica, magnesium, sulfur, aluminum, sodium, calcium etc. Carbon, oxygen, and nitrogen provide a framework for making organic matter that constitutes living organisms. These elements make volatile molecules. The meteorites were heated while passing through the primitive atmosphere and the volatile components such as carbon dioxide, water and nitrogen would have released to the primitive atmosphere.
Both comets and asteroids were possible as small objects that supplied water to the ancient Earth. In the past, the comet would have supplied water to the Earth. Comets have a main component of ice with dusts around the icy core. On Halley's comet, 80% is ice. However, when the Rosetta space probe surveyed the components of the Gerasimenco comet in 2014, it was found that the hydrogen isotope ratio was significantly different from that of the Earth's sea. At present, the asteroid is thought to be a dominant water source.
The early Earth was cooling rapidly, so different material layers were kinetically confined locally. Especially the hot interiors were separated from the surface. This means the Earth is far away from thermal equilibrium. The Earth constantly radiated heat towards the Universe and lost some materials. The surface of the Earth constantly obtains energy from an external light source called the Sun, and the surface of the Earth's crust and atmosphere is affected by it.
At the final stage of the formation of the Earth, a protoplanet (called Theia) collided with the Earth, which has about 10-15% of the mass of the Earth (similar size as the Mars). As a result, the last 10% mass was added to the Earth, but the surface layer of the Theia and the Earth splashed around the Earth (Giant Impact). The materials which revolved around the Earth gathered again to form the Moon as an independent celestial body. It was 4.53 billion years ago deduced from the age of the moon rock. The birth of the moon was around 90 million years since the birth of the solar system.
According to a simulation, when a collision occurred on the primordial Earth in the state of magma ocean, the magma blew out as a jet, which became a disk in the Earth's orbit and eventually formed the moon. At this time, after the collision, the material of Theia and the material of the magma ocean scattered around the Earth. The Theia's material immediately collided with the Earth again. On the other hand, the Earth's magma ocean component remained in orbit, so the moon contained 70% of the Earth-derived component. It can be explained that the isotopic ratio is the same between the moon and the Earth's crust. If the magma ocean cooled and hardened smoothly, the precious metal should only be found in the core. The presence of them on the surface of the Earth is explained by the giant impact.
A part of the Theia's iron core and other materials were melted and covered the Earth like a cloud. The metallic vapor as a storm took oxygen atoms from water molecules and metal oxides sunk into magma ocean. The remaining hydrogen covered the Earth as a thick atmosphere for about 200 million years. On the Earth immediately after the magma ocean solidified, rocks covered the surface of the Earth, and carbon dioxide, nitrogen and sulfur dioxide erupted from the Earth. When a hydrogen blanket was applied in this state, organic compounds with a low molecular weight were synthesized. 4.46 billion years ago, the Earth was cold enough to have the Sea, and it was estimated that RNA was produced 4.35 billion years ago.
At the time of formation by Giant Impact, the Moon was in the vicinity of the Roche limit (the distance inside where a satellite was destroyed by the tidal force, about 50,000 km from the surface of the Earth). At that time, the Earth rotated about 6 hours, the moon had one lap in 10 hours. Friction due to the tidal force was produced by the deviation between the moon's revolution and the Earth's rotation cycle. As a result, the rotation of the Earth decelerated, the moon was accelerated and moved away.
After the ocean was formed on the Earth, the great tidal power produced a height difference on the Sea, and it is thought that the height of the wave had reached 1000 m. Supposing that the estimated ancient ocean depth would be 2000 m, a huge and intense wave had been washing the surface of the Earth continuously. Also, the solid part of the Earth was flattened, then the equatorial diameter was nearly twice the polar direction. On the Archean Earth, arcuate islands formed by plate tectonics were washed away by tidal waves and craters made by gigantic meteors in the late heavy bombardment (4.1-3.8 billion years ago) would be also buried and flattened. Since the magnitude of the tidal force is inversely proportional to the cube of the distance from the Earth to the moon, the effect of tidal friction drastically weakened, and the Earth’s surface is thought to be stable in hundreds of millions of years.
Tidal force converts the energy in gravity potential into heat. It is an important mechanism that fundamentally dominates the evolution of the planetary-satellite system, such as heating the entire satellite, changing the internal structure, changing the orbital motion by generating a gravitational torque. At present, phenomena are observed that tidal energy dominates between Jupiter or Saturn and their satellites, that is, activity of Jupiter's Io and ice ejection activity of Saturn's Enceladus.
In the Precambrian era of 900 million years ago from now, it is estimated that one day of the Earth was 18 hours. At this time, a year was about 480 days, and the distance to the moon is about 350,000 km. In the past several hundred million years, the rate of the deceleration of speed of the Earth's rotation (= the speed that the moon goes away) is also nearly constant. The change in the distance from the Earth to the moon is measured to be 3.8 cm each year in present, using the mirror placed on the moon by the Apollo project.
Examining the samples brought back by the Apollo project, the surface of the moon is entirely made of igneous rock. The white areas are old-fashioned and are members of the granite family (anorthosite, a rock containing many feldspars). The dark areas were made of basalt about 3.5 to 3 billion years ago. After that, there would be no magma activity in the moon. From the seismic wave meter installed in the Apollo project and the deformation measurement caused by the tidal force with the lunar orbiting satellite Kaguya, the moon has a core with a radius of 300 km, a mantle with a radius of 1400 km, and a crust of about 10 km.
Observation of the moon craters estimates that most of the craters were made intensively about 4.1 billion years ago by impacts of asteroids in the orbit between Mars and Jupiter deduced from the size distribution. A mechanism of this phenomenon was studied by simulation. It was approximately 4.1 billion years ago when Uranus and Neptune were formed. The formation of these two planets is thought to have displaced the orbits of Jupiter and Saturn, then the orbit of the asteroids was also influenced. The orbital change of the giant planets disturbed the orbit of asteroids, then many asteroids flutter in the solar system. Approximately 4.1 billion years ago, asteroids have fallen as meteors to the Earth during from tens to hundreds of millions of years and is called the late heavy bombardment. Since they were meteorites from the outside of the snow line, a large amount of water and carbon compounds were supplied to the Earth at this time. The depth of the sea of the primitive Earth is estimated to be approximately 2000 meters. The surface of the Earth was almost covered with the ocean. There was a basaltic crust below the sea and a thick atmosphere above the sea.
The number of meteorites that fell to the Earth during the late heavy bombardment period is estimated to be 22,000. Craters with size of 2000 km were estimated to 40, and those of 5000 km were expected to be several. These gigantic meteorites had several hundred kilometers in diameter, completely dried up the sea, broke through the crust and disturbed the upper part of the mantle. The rock temporarily melts, the substance in the mantle was pumped up to the surface, and the substance on the crust was embedded in the mantle. The collision of the meteorite caused the sea and lava to splash into the atmosphere, producing a large amount of aerosol, and mixed with the atmosphere. The sea recovered safely even after the gigantic meteorite collision. Lava was cooled by the sea, and brought various substances to the sea. The basaltic crust revived by rapid cooling of the lava.
When a celestial object collides with the crust, a large amount of crash debris called ejector is generated. Among the ejectors, particularly fine ones are susceptible to chemical weathering reaction because of their large surface area. A large amount of ejector was generated by frequent collision of the heavenly bodies, as a result, carbon dioxide (carbonate ion) dissolved in the sea precipitated as carbonate. Therefore, carbon dioxide in the atmosphere gradually declined.
At that time, the Sun emitted only about 70% of the current energy. With this amount of radiation, the Earth froze all over. The frozen Earth melts rapidly due to the fall of the meteorite, and sometimes the sea may have repeatedly evaporated completely. If the amount of carbon dioxide is large, there is a possibility that the Earth did not freeze due to its greenhouse effect.
Impact experiments on small meteorites have shown that meteorites become powdered at the surface of the sea. At that time, organic matter may have been free from decomposition by impact heat. In addition, the fine meteorites may have reached the terminal velocity with the atmosphere as a cushion, and was continuously deposited in the sea. If a large amount of fine meteorites remained after the formation of the Earth, it is possible that the organic matter was supplied on the Earth.
By my personal view, it is probable that when the meteorite fell and the sea and the rock evaporated, the carbon compound was carbonized by heat and highly reactive metal carbide was formed. It seems that metal carbide molecules bonded to each other to modify them and developed into polymer compounds. The collision of the meteorite may have supplied new substances, complex organic matters and compounds.
The oldest rock existing is 4 billion years ago (exactly 4,030 million years ago). Rocks made after 3.8 billion years ago can be found in many places. Sedimentary rocks are also found. From these results, it seems that rocks have been preserved stably since 3.8 billion years ago. The sea seems to have stabilized since 3.8 billion years ago after the end of the late heavy bombardment period.
Due to the giant impact, the Earth melts again completely, and the surface was considered to be solidified at 4.53 billion years ago. After the giant impact, the atmosphere was relatively thin until about 4.1 billion years ago. The early meteorites that formed the Earth were enstatite chondrites, which were poor in volatile components. Since the Earth located inside of the snow line in the solar system at that time, the volatile components were blown off as gas outwards to the solar system by the solar wind.
When the magma ocean cooled, komatiite with a high melting point was deposited on the surface. The first crust on the Earth is thought to be komatiite. Like olivine, komatiite is low in silicon dioxide and rich in iron and magnesium. When the same ingredients slowly cool and harden, olivine is formed. Olivine is the main component of the current mantle.
The late heavy bombardment period began about 4.1 billion years ago. The meteorite at that time was carbonaceous chondrite, which had a large amount of volatile components. The late heavy bombardment brought much water to the Earth, and created the sea.
The pillow lava is one of evidences of the presence of the sea. It has a characteristic form because lava was blown into water and cooled rapidly. Oldest pillow lava was found of 3.8 billion years ago in Isua, Greenland. A metamorphic rock made from granite of 4 billion year ago was discovered in the Acasta area in the northern Canada. Granite shows the presence of plate tectonics and the sea.
At first, water turned to rain at high in the sky where the atmospheric pressure and temperature were low, but evaporated before it reached the surface of the Earth. As the atmosphere cooled down, the rain gradually reached a low position. Steam becomes liquid water when it becomes at 100 atmospheric pressures and 650 K (380 C) or less in absolute temperature. This temperature is called the critical temperature of water. When the primordial atmosphere was 100 atmospheric pressures (mostly considered carbon dioxide), the first rain fell to the ground when the surface cooled to around 300 C. It was a decisive incident that the Earth had a different dress from other planets.
The sedimentary rock on the surface of the Earth contains carbon which corresponds to as high as 90 atmospheric pressures in terms of carbon dioxide. This pressure is almost the same as Venus' atmosphere. The atmosphere of Venus consists of rich carbon dioxide and nitrogen. At the top of the atmosphere of the same depth of the Earth's one, the temperature is lower than the Earth. Below that there is a dense and high-temperature atmosphere of 50 km. As the altitude lowers and the pressure increases, it gets hotter. It reaches 400 C at the bottom of its atmosphere.
Rain efficiently cooled the surface of the Earth. The early crust, komatiite, sank into the mantle by plate tectonics, instead, a basaltic crust was appeared on the surface. Hydrogen chloride was dissolved in the rain, so it was strongly acidic. Rain water containing hydrochloric acid dissolved ions such as magnesium, calcium, aluminum, sodium, potassium, iron from rocks on the ground and was neutralized.
A large amount of carbon dioxide in the atmosphere dissolved in the primitive ocean, bonded with calcium ions and precipitated as calcium carbonate (limestone). Plate tectonics transported heavy metals from seawater to the mantle. Carbon dioxide contained in the primordial atmosphere fell to about 10 atmospheric pressures and the greenhouse effect of the atmosphere by carbon dioxide was relieved. The primordial atmosphere at that time consisted of 90% carbon dioxide and 10% nitrogen. Around hydrothermal plumes in seawater, carbon dioxide and carbonate ion concentrations were high. The hydrothermal alteration of the oceanic crust made carbonate minerals crystallize, then the silicate concentration increased in the hydrothermal ejection, calcium ions in the seawater decreased, and the concentration of the phosphoric acid increased.
In the rocks formed by the Earth's plate tectonics system, the oldest one discovered so far is 3.8 billion years ago. A series of rocks formed along with the division of the ocean floor was discovered in Greenland by an International Research Team. Therefore, the system of plate tectonics seems to have started relatively early in ancient Earth. This rock is called an ophiolite, a characteristic layer structure which an oceanic crust is exposed to the ground. It is of thickness about 10 km which is equal to the thickness of the oceanic crust, including various kinds of volcanic rocks.
During about 1 billion years after the birth of the Earth, the atmosphere and the sea were agitated violently by the tidal action of the moon which was very close to the Earth and impacts of meteorites. The molecules that constitute the living body had been steadily accumulating. Hundreds of plates are crowded together on the Earth's surface in the Hadean eon. The plates collided, but both were so young plates that subduction hardly occur. The plates were folded to upraise at the subduction zone. The magma was not formed from the plate that had slipped under another plate as the present day. The plates were bent and pushed into the mantle, then became magma in the deep. In this case, a folding mountain range was formed at the plate boundary, and a volcano is formed in the center of it. The magma was compressed from both sides and spouted out to the sea, forming islands. Arc-shaped islands formed and grew along the plate boundaries.
The ocean current which had become a laminar flow along the latitude was to be stopped at the arc-shaped islands. The seawater which had been circulating independently at the surface and in the sea floor has welled up and settled down at the arc-shaped islands. Also, the waves that hit the rocks at the shore broke and flew away as droplets. The organic matters synthesized at the bottom of the ocean traveled all the way to the sea surface, splashed at the sea surface and flied up to high altitude. They chemically reacted with the organic matters which synthesized at the sky, resulted to form other type of organic molecules there. Then the insoluble minute organic matters fell to the surface of the sea as rain and sunk and returned to the hydrothermal vent. Organic synthesis was accelerated by ultraviolet light in the sky, and also received moderate decomposition.
The volcano rising in the sea were blowing a plume up, and supplying fine particles to the atmosphere. The fine particles became the core of cloud water droplets, and the Earth was covered with clouds more than before. Clouds cut ultraviolet rays that decompose heterocyclic compounds. Since the sun's radiation at that time was weak, the Earth may have been covered with ice globally. Heterocyclic compounds may have been able to convert light energy to chemical energy under ice without being destroyed by ultraviolet light.
Well, this chapter is just my guesses. How much was the concentration of carbon in the primitive Earth? First, considering the current amount of water in the sea is 1.35 billion km3 and the total carbon circulation amount on the surface of the earth is 50 trillion tons (both values are from Wikipedia), the concentration of carbon is assumed to be about 3.6%. Second, assuming the depth of the primitive ocean 2000 km, and the current crustal weight of 2x10E16 tons and the proportion of carbon contained in crust is 0.03%, the proportion of carbon dissolved in the sea as 1%, the concentration of carbon in the primitive sea is assumed to be 6.6%. When referring to the water content of silk tofu and milk is 90%, the sea of the primitive Earth may have been muddy with organic molecules more than expected.
At the zone of mantle plume, an ocean ridge is formed and hot water spouts up as a line. They were at the deep sea floor of 2000 m. In the place where the plate collided, magma warmed the seawater and also formed a hot water spout (a hot spring). This place was at depth of about 100 m at the shallow sea bottom near arc-shaped islands. One hypothesis on the birth of life would be here a hot water spout at the shallow sea floor. Caldera volcano under the sea was pushed from both sides and gradually uplifted, became a bay and finally became a lake. From the speed of uplift of the Himalayas and the Alps, it will be landed in tens of millions of years. This process poses a hypothesis that sufficient enrichment for birth of life would have occurred during this time. Presumable primitive life organisms born in the volcano lake would have been returned to the mother sea.
The plates moved on the mantle convection. At the place where two plates collide, one plate will be on top and the other will sink into the mantle. It is called a subduction zone, and the arcuate islands grew. The plates are generated where the mantle gets up. It is called the ridge. In Archeozoic era, the total extension of the arcuate islands and the ridge on the Earth would have been nearly 20 times those of the modern era.
In the ridge, cracks were formed in the bottom of the ocean by the mantle which springs up, magma was supplied from the rising mantle, and a basaltic crust was formed. In the ridge, hot water blew out of the sea floor due to the heat brought from the mantle, and a large amount of reducing gas such as hydrogen sulfide, methane, hydrogen and metal sulfide such as iron and manganese was supplied to the sea. The depth of the sea of the primitive Earth is estimated to be approximately 2000 m.
In the subduction zone, the trench was formed. Since the subducted plate contains water, it melts at a relatively low temperature in the mantle. It supplies magma which squirts to the sea, making a submarine volcano including a large amount of granite. Eventually, an orogenic belt is created along the plate boundary, and the islands develop. Probably the island would have been arcuate. Volcanic activity released reducing gases such as hydrogen sulfide, methane, hydrogen from the ground into the ocean and the atmosphere. The sinking plate left numerous adornments on the arcuate islands. Even if there was a precipitate of organic matter at the bottom of the sea, they were rarely buried deep in the ground.
The land that existed on the primitive Earth is expected to be only the island. Orogenic movement occurred in a large scale where the plate collides, but no evidence is left. Lands affects flows in the ocean and the atmosphere. If the land is small, the clouds will not be like the present complicated pattern, but they will have been regularly lined up like striped patterns seen on Jupiter and Saturn, due to the influence of rotation. It seems that flows of the ocean were regularly arranged in the same way and were layered. Sedimentary rocks, if made, are in a small amount. Up to 2.8 billion years ago, the continent is only about 20% of the current lands.
Looking at the completeness of living organism in present, I am surprised that hundreds of proteins are involved in one living phenomenon. Common cellular activities include gene replication, gene transcription, translation of mRNA, synthesis of proteins, transport of secreted proteins, processing of proteins, synthesis and degradation of lipids and amino acids, photosynthesis, glycolysis, TCA circuits, ATP synthesis driven by membrane potential, protein degradation, intracellular degradation of organelle, secretion of molecules and so on. Furthermore, replication of these molecular devices is attained.
Protein is a very complex molecule and functions as a nano-machine. Many kinds of proteins are gathered to create huge structures and work together in series. Nucleic acid responsible for genetic information cannot act on its own and always needs assistance of many proteins. In the system from gene to protein synthesis, nucleic acids and proteins cooperate together.
The membrane structure is not merely a shield against the outside world. The protein embedded in the membrane creates a non-equilibrium state on both sides of the membrane to produce energy (ATP) and also sends nerve pulses. Membrane protein also takes extracellular nutrients and catches information molecules. Eukaryotic cells have many folded membrane structures in the cell and carry out a special reaction in the isolated space.
In fact, in order to elucidate the process of the creation of life, it is necessary to clarify how these functional units were born from inorganic molecules, but also how each functional unit interacts to create an organic relationship among them. Even if these parts are prepared and are mixed, living system cannot be born. Was it inevitable that life was born? Or have many incidents stacked in very long time? It is still unknown, and even putative clues for elucidating it are suspicious.
The essence of life is information. That is, the information that constructs the molecule functionally as an organism is the essence of life. The key to elucidating the birth of life is the birth of information necessary for life, the material basis of information, and the mechanism by which information is replicated to the next generation. Currently, the first genetic information molecule is considered to be RNA. However, we must consider how information on the amino acid sequence of the protein has been written to the RNA molecule.
For the birth of life and its early evolution in several following chapters, I am assembling fragmentary scientific reports into an inevitable story to make a hypothesis on the origin of life.
In order to organize the researches on the origin of life and to align them along the time, I consider how molecular and molecular devices that make up the living body were created from a simple one to a complicated one. The following items are scheduled as follows. Up to "the mechanism of heredity" is the construction of parts, after that it corresponds to the assembly of parts.
But maybe the opposite way of thinking can be possible. It is possible that massive carbon clusters (substances such as graphite or fullerene) were geologically born from carbonate rocks (limestone, etc.) in a reductive environment. Or the possibility that the mountain of carbon decomposes slowly in the seawater to generate macromolecules. As I will repeat in the following chapters, the sufficient density of the molecules involved in life activities is not considered to have been produced naturally. I think that a strong concentrating process is necessary. The story that cells are made simply by assembling molecules is contrary to the second law of thermodynamics. Considering that a carbon polymer of mountain size of high energy state was born on the primitive Earth, problems of concentration and molecular aggregation could be solved.
How long has it been until the birth of life? The Hades era was till the late period of heavy bombardment was over at 3.8 billion years ago. After that, until 3.8 to 2.5 billion years ago is called the Archean era. The fossil was found of the first cell (with a membrane structure) about 3.5 billion years ago.
When the sea was appeared, the Earth is covered with thick clouds. At that time, water vapor, carbon dioxide, and nitrogen were turned into reactive radicals by ultraviolet rays from the Sun, particle beams from the space and lightning discharges in the sky. Then chemical reaction among these molecules and the radicals made simple organic compounds, such as hydrogen cyanide, cyanoacetylene, formaldehyde. Organic substances were sometimes supplied from meteorites and meteors. These molecules melted into raindrops and dropped to the sea. There were very small lands in those days. Most of the highly reactive material molecules reacted with water, but sometimes they mutually reacted to form large molecules, stabilized, and accumulated in the primitive ocean.
Biomolecules that make up a living organism include carbon, nitrogen, hydrogen, and oxygen as main constituents, and other elements such as sulfur, phosphorus. Carbon and nitrogen constitute the backbone of the biopolymer. Carbon has four arms that form a covalent bond, and nitrogen has three arms. Oxygen has two and hydrogen has one arm. Molecules are constructed in the way that these arms are fully connected. Compounds which have carbon skeletons are called organic substances.
A large amount of organic material exists in the universe. The Earth was supplied with a large amount of ice and volatile organic matter at the late stage of heavy bombardment of the meteorite, which was carbonaceous chondrite. Most of them are silicate minerals, containing metallic iron, ice and 2-3% of amount is organic substances. Carbon and water contained in the meteoroids in outer space are activated by ultraviolet rays coming from the Sun and particle beams to activate them, and a chemical reaction is caused to synthesize an organic substance having a simple structure.
Organic substances brought in at the time of the Earth construction would have been decomposed in the magma ocean era finalized by the giant impact. There would have been a lot of carbonaceous chondrite meteorites that fell after magma ocean era. Organic substances were possibly decomposed by the frictional heat with the atmosphere. Since the meteor that fell on the earth is simply an aggregate of sand-like grains, it decomposed at high altitude before the temperature rose, and the organic matter in the meteorite would be brought into the atmosphere without being decomposed.
In the Archeozoic era, there was magnetic field around the Earth due to the convection of the Earth’s metal nuclei, so the upper part of the atmosphere was protected from charged particles coming from the Sun. Heavy organic matter synthesized in the sky fell into the sea by atmospheric circulations after condensed. Organic matters soluble in water reached the sea as rain drops. While falling with raindrops, there was a possibility that organic matter was concentrated through evaporation, and the polymer was synthesized during it drifted as a cloud. In the volcanic eruption, many lightning occurs together with reducing gas and water vapor. Reproducing this environment in experiments also made complex amino acids.
Amino acids and nucleobases are well studied as low-molecular organic compounds made first, because these are important components of living organisms. It seems that many other molecules have been synthesized, but they have not been studied much. Organic compounds with a molecular weight of about 1000 are discovered in large quantities from the biological world in large quantities. It also contains many useful substances, such as antibiotics. Amino acids and nucleic acids are molecules having about several to several tens of atoms with a molecular weight of 100-300. From these types of molecules, molecules with a molecular weight of about 1000 were synthesized and accumulated by catalytic action of high concentration metal ions in the hydrothermal vents at the bottom of the sea through thermochemical reactions. Those molecules contain multiple functional groups in one molecule and would assemble to form the base for a new chemical reaction.
Amino acids are synthesized through the famous reaction starting from aldehyde and hydrogen cyanide, ammonia. Besides that, decomposition of nucleic acid bases can be considered. Saccharides with simple structure can be synthesized from formaldehyde. The mineral consisted of boric acid acts as a catalyst. Although sugar has many three-dimensional structures even with the same molecule, among them, fructose, glucose, and mannose are stable, and it is considered that the sugar plays an important role in origin of life.
A cyclic molecule consisted with 6 or 5 atoms of either carbon or nitrogen, alternatively bound via single and double bonds, is called a hetero ring. Adenine, one of the nucleobases, has a heterocyclic structure in which hexagons and pentagons are fused. Adenine can be relatively easily synthesized from hydrogen cyanide and ammonia. Heterocyclic molecules containing nitrogen like adenine are bonded to each other weakly by hydrogen bonds and are easy to make complexes with metals. As it contains double bonds in a molecule, two double bonds react and tend to polymerize via radicals. Because it is easy to decompose with ultraviolet rays, the nucleobase is unstable at the surface of ground or in the sea, where the ultraviolet rays reach.
At bombing into the sea of a meteorite containing metallic iron, reductive atmosphere of ultra-high temperature was temporarily generated in the area. When a meteorite collides with the ocean, a large amount of water instantaneously turns into supercritical water and ultrahigh temperature gas, at the same time, the meteorite and the mineral components of the sea floor evaporated together and became a so-called after-impact steam flow. In ultra-high temperature post-impact steam flow, water decomposes into hydrogen and oxygen. Metallic iron and oxygen in the collision body reacted and became iron oxide. After the collision, the steam flow reached a reduction state of excessive hydrogen at once. Concomitantly, the iron sulfide and the peridotite were evaporated to work as reductive steam flow. As the temperature of the steam flow decreased from ultrahigh temperature, carbon reacted with the hydrogen generated to produce hydrocarbons and various other organic molecules. It is a chemical reaction known as Fischer-Tropsch synthesis and requires a transition metal such as iron, nickel, cobalt as a catalyst. These metal elements also evaporated at high temperature and coexisted in the steam flow.
Cyclic organic compounds having a benzene ring or a hetero ring are indispensable for basic molecules of living things. These organic substances are easily decomposed by ultraviolet rays. Elements of organic molecules in the sky or on the ground were decomposed by exposure to ultraviolet light even when they were synthesized. The place where biological macromolecules necessary for living organisms were born, preserved, and formed higher-order structures (this is called chemical evolution) was on the ocean floor where ultraviolet rays could not reach.
The first candidate of the place of birth of life is around the hydrothermal vent on the seafloor. One of the reasons is that hyper-thermophilic bacteria are located at the trunk (starting point) of molecular evolutionary tree. On the Earth in present, superheated bacteria are isolated from the hydrothermal vents of the seafloor. Other candidates, such as in volcanic activity on the ground (hot springs), collision of meteorites, and lightning, are lacking of stability in view of energy supply.
Seawater from black smokers formed in the hydrothermal area contains high concentrations of hydrogen. Hydrogen is generated when peridotites in the mantle react with hot seawater and turn into serpentine. In the proto-Earth, komatiite, formed by rapid cooling of magma, formed the crust, so komatiite is considered to be the source of hydrogen. At the present seafloor, hydrogen concentration of about 20 mmol is observed in the hydrothermal area originating from the ridge in the deep sea of 500 atm or more. Hydrogen is essential for reducing carbon dioxide to produce organic matter. An oxidation-reduction potential is formed around the hot water jet, thereby providing a fuel engine with stable performance due to a difference in concentration of a substance and a difference in temperature. It is convenient for the synthesis of organic compounds.
Furthermore, the seawater from the hydrothermal vent contains more than 1000 times more metal ions such as iron, manganese, copper, zinc than ordinary seawater. Metal ions act as a catalyst for polymerizing organic substances under high temperature and high pressure.
The hydrothermal vent is in an environment of high temperature (200-350 C) and high pressure (200-300 atm), and a large amount of heat energy is constantly supplied. Cold seawater infiltrated from the cracks of the ocean floor is heated in the bottom of crust, rises up the jet hole, blows out into the cold seawater, and is cooled again. The heating / cooling cycle of seawater occurring in the hydrothermal vents is reasonable when considering chemical evolution. Organic polymers that play a central role in life activities are unstable in high temperature environments. Organic materials synthesized at high temperature were immediately cooled at the sea bottom hydrothermal vent, so it was possible to avoid decomposition by heat.
As the sea water circulates, the organic molecules have passed through the hydrothermal vents many times over the flow and have grown into more complex molecules. Polymer compounds were filtrated from seawater containing organic matter when passing through mud, rock or crust, and being precipitated and concentrated there. For example, when considering that the reaction has progressed one step at each cycle, it fits well with the fact that the biopolymer is a linear homopolymer.
Biopolymers are generally linear homopolymers of amino acids, nucleobases, sugars. There are reports that amino acids and nucleotides adsorbed on the surface of clay minerals are polymerized, suggesting one of polymer formation mechanisms. In ancient times, low molecular weight organic compounds such as amino acids, nucleobases, sugars, fatty acids, hydrocarbons, etc. bonded to regular crystals (the surface of minerals) become polymers (linear homopolymers), this is one of theory on chemical evolution.
Another theory is to think about oil production. It is possible that sediment containing a lot of organic substances buried in the ground, undergo dehydration reaction under high temperature / high pressure in the underground, and turned into a substance like petroleum containing a large amount of unsaturated carbon bond. Petroleum-like low molecules tend to cause chemical reactions and easily polymerize at normal temperature and pressure. If a massive amount of organic matter was buried and became petroleum, it would have formed a layer like current petroleum and a high concentration of organic resources would have been generated.
Volatile organic molecules decompose with ultraviolet irradiation or such rays falling over in the sky on the primitive Earth. Nonvolatile organic molecules are dispersed in the sea. Molecules with small density and of water-insoluble like oils floated and agglomerated on the sea surface. In that case, it is decomposed on the sea surface where ultraviolet rays are falling or it is radical polymerized into a polymer. Water soluble molecules such as amino acids, nucleic acids and sugars dissolve in seawater, adsorb to clay minerals and precipitate on the seabed. In general, biological organic molecules have high affinity for clay minerals.
The hypothesis that life was born on the ground, such in shallow sea or lake, has advantage in view of enrichment. Concentration of substances occurred on the surface from the tidal dry-wet cycle, which led to synthesis of macromolecules. The problem in pre-life evolution and chemical evolution is the mechanism of supply of macromolecules and how the combination and structuring of macromolecules to create life phenomena have been achieved. At present, several proven synthetic reactions have been reported, and it is likely that living organisms will be formed if they are conveniently combined. However, no matter how you describe it, the drawback is that it looks like expediency.
Ammonia and cyan produce numerous polymers containing nucleobases. As this process proceeds simultaneously, explosive number of types of compounds are produced. However, under the presence of phosphoric acid, this reaction is limited to some extent. In the experiment, 2-aminooxazole is synthesized in the presence of phosphoric acid. This compound is a promising precursor of nucleic acids containing pyrimidines. Also, it is volatile and easily solidifies. That is, 2-aminooxazole is possible to be concentrate by increasing and decreasing the temperature. In the process of synthesizing a nucleic acid containing pyrimidine from 2-aminooxazole, there is no need to consider the reaction in which a sugar, a nucleotide base and a phosphate group are bound, which is one of the keys of nucleic acid synthesis on the primitive Earth.
Chlorophyll and hemoglobin (heme) are molecules in which heterocyclic molecules are coordinated to metal ions (magnesium for chlorophyll and iron for heme), to form complexes. Heterocyclic molecules such as nucleobases absorb ultraviolet rays and become activated. Molecules with many heterocyclic molecules, such as nucleic acids, are activated by UV light. Complex molecules composed of heavy metal ion and heterocyclic molecule were born on the ancient Earth, and formaldehyde was made in large quantities from water and carbon dioxide by catalysis of metal ion activated by sunlight.
When carbon dioxide and hydrogen react with the catalyst of a heavy metal complex, formaldehyde is formed. Formaldehyde is a reactive substance and has the property of polymerizing itself, resulting in paraformaldehyde or a sugar. In addition, it reacts easily with chemical groups forming a hydrogen bond. As a result, intramolecular and intermolecular bond are formed. Molecules in living organisms, such as sugars, proteins, and nucleic acids, that make up the living body have abundant hydrogen bonds and react with formaldehyde. Among alkaline liquids, formaldehyde undergoes a polymer synthesis reaction which produces various sugars. The macromolecule of sugar is insoluble and highly reactive.
Further to imagine, the heterocyclic molecules-heavy metal ion complex, which produces formaldehyde from carbon dioxide using light energy, was linked each other by products, then stabilized and accumulated in large quantities. I think this is the origin of photosynthesis.
On the other hands, the reaction that reduces iron sulfide with hydrogen sulfide to produce pyrite reduces carbon dioxide to form formaldehyde and formic acid. In the deep sea where sun light cannot reach, carbon dioxide assimilation by chemical energy spontaneously occurred. The iron sulfide produced as a result is insoluble and precipitates in the form of a foam. The catalytic center of carbon dioxide assimilation may be encapsulated in an iron sulfide capsule and serve as a source of cells. It is called the Hall & Russell hypothesis.
The hot water ejected from the seabed floats and rapidly mixes with the surrounding cold seawater. While rising, the dilution of hot water progresses steadily, and when it reaches about several hundred meters from the seabed, the temperature (density) of hot water becomes equal to that of the surrounding seawater. The original hot water that has lost buoyancy spreads horizontally on the equal density surface. The original hot water is diluted but contains fine sulfide and oxide precipitates.
Compounds having high energy as chemical bonds are necessary for enzymes to carry out synthesis reaction under the body temperature. Current cellular organisms utilize molecules that can carry an active state as chemical bonding energy. It is adenosine (a molecule composed of a nucleobase adenine and pentose bound). Adenosine triphosphate (ATP) carries high-energy phosphate bonds and NADH and NADPH carries redox state, both contain adenosine.
The high-energy phosphate bond of ATP seems strange molecule in which three phosphate groups are connected in series. When phosphoric acid is heated, a dehydration reaction occurs, and two or more phosphoric acids react at 200-300 C to produce pyrophosphoric acid (diphosphate) and polyphosphoric acid. It is easy to decompose in aqueous solution, but it is synthesized as a polymer compound in hot water. The process is unknown to use phosphate groups for biochemical reactions in chemical evolution. Considering the principle of biological evolution that one uses matter available there, adenosine and phosphoric acid would be abundant in the place where life was born. In addition, at the hydrothermal vent, where considered as a place of life creation, polyphosphoric acid would have been synthesized in the underground of high temperature region if phosphoric acid was abundantly dissolved. Polyphosphoric acid might be used as an energy source for chemical evolution where injected into the seawater in a moderate temperature range. ATP appears everywhere in biochemical reactions. Coenzyme, which is a small molecule that works at the active center of the enzyme, also contains heterocycles (heterocyclic compounds) consisting of adenosine and carbon and nitrogen.
There are many reactions in vivo that bind phosphate groups through chemical reactions to the substances for further processing. For this purpose, the carrier of the phosphate group is ATP and other coenzymes and vitamins. A glycolytic system for metabolizing sugars is a typical example. In addition, FADH and NADPH, which are carriers of protons (hydrogen ions) and electrons in the redox reaction, contain phosphate groups.
Furthermore, a group of molecules containing sulfur is also involved in energy production and polymer synthesis. The iron sulfide complex is located at the active center of the enzyme at the entrance of the TCA circuit, which locates at the center of energy production. Sulfur-containing coenzymes provide methyl and acetyl groups. The skeleton of these coenzymes is a heterocyclic molecule composed of carbon and nitrogen, and is composed of 1 to 3 heterocyclic rings. Since there was almost no oxygen on the molecule in the Earth of the Hadean eon, heterocyclic compounds were rarely decomposed by oxygen.
Sea water containing a large amount of iron ions, phosphate ions, carbon dioxide was circulating through the crust around the hydrothermal vent. Around the heat source at the bottom of seafloor, the temperature is high, and in the reducing state, precipitates of metal ions and molecules containing high-energy bonds are formed. Since the temperature of the seafloor is low and being the oxidation state there, high-energy bond was converted into covalent bond between molecules. The non-equilibrium state which is the energy source of living activity was maintained in the temperature gradient and redox state.
My hypothesis is that the foundation of chemical reaction was initially the surface of minerals, but eventually developed to the surface of macromolecules containing heterocycles, and further to the surface of proteins (enzymes). As the activation energy is lowered by the catalytic action, the driving force of the chemical reaction by the temperature gradient was taken into the cell, and evolved into a modern life activity, which does not require a high temperature to work
The mystery of the origin of life lies in the dilemma that the genetic system cannot function unless it would be formed at once. Proteins cannot be made simply after amino acids appeared. That is, even if a monomer of a biopolymer is formed, a polymer cannot be formed. Molecules necessary for living activities should have been born by numerous chemical reactions since the sea was formed. Molecules with autocatalytic ability capable of synthesizing themselves by themselves should have accumulated in large quantities. Molecules that produce themselves can be considered to carry genetic information. In current organisms, responsive molecules for genetic information and for function are different. In this case, genetic information does not function without a device for reading genetic information. It cannot be said to be inherited if impossible to synthesize (replicate) the molecule responsible for genetic information. This leads to a discussion on whether chicken or egg is ahead.
One of the characteristics of the heredity of terrestrial organisms is that the genetic information is one-dimensional. Genes are polymer of units arranged in one dimension and functional molecule are polymer of another type of unit arranged in one dimension. Units have functional groups for bonding. By simply combining them, random polymers are formed. In order to have information, the sequence and synthesis system (catalyst) must be linked. Coupling is a mechanism for specifying the order of synthesizing unit molecules. This is the replication device. The information of sequence is included in the one-dimensional array of the molecule.
The nucleic acid which is the main body of the current genetic materials uses hydrogen bonding between heterocyclic ring to forms a pair. The machine specifies a sequence of newly synthesized molecules by making a pair. In the course of chemical evolution, nucleoside molecules are made, they are aligned in a row by stacking interaction of nucleobases, and if they are bound to an appropriate catalyst surface, phosphate group and ribose can bind to synthesize RNA. At this time polyphosphoric acid is involved as a catalyst and energy source. RNA molecules can make three-dimensional structures due to stacking interactions and hydrogen bonding between nucleobases. Due to the complementary relationship of hydrogen bonds, RNA has the property of pairing with a fixed base.
RNA has also an enzymatic reaction. It is known that an RNA molecule having a specific sequence cleaves a molecule, and an RNA having another sequence binds RNA. They are called ribozymes like enzymes. In a ribozyme, an active site that causes a chemical reaction is formed by assembling heterocyclic rings by arranging nucleotides in a certain sequence.
When a certain type of ribozyme was born, which facilitates the synthesis of its own complementary nucleotide, it increased its number by using the nucleotides in the environment. This is a positive feedback reaction pathway. One ribozyme catalyzes one chemical reaction, but the continuous arrangement of ribozymes connects the catalytic reactions. Molecules flow in this array of ribozyme to be processed into complex molecules. Ribozymes capable of replicating ribozymes were born after a long time by miraculous chain of events. Once such a positive feedback reaction pathway has been formed, it has become possible to synthesize the parts of living organisms as subspecies. From these hypothesis, a model in which RNA evolves while self-replicating, the RNA world, is considered.
Molecular complexes able to replicate and grow on a special catalytic surface have come to have the complexity and some scale enough to replicate themselves after a long time. This is called a two-dimensional life form theory. The problem is that two-dimensional life forms lose their lives when they detach off from the catalyst surface. The simple way to confine it is in the vesicles.
When a heterocyclic ring containing carbon and nitrogen is cleaved, it becomes a molecule having an amino bond. If array of the nucleotide bases linked with hydrogen bond is partially cleaved, electron transfer of the double bond occurred to form a linear oligopeptide. I present the hypothesis that such an oligopeptide binds to the end of a heterocyclic ring molecule, which has evolved into a protein synthesis system. This heterocyclic complex is considered to be an ancestor of transfer RNA.
So far, I have introduced the would-be reactions in the natural world that made the molecules of living organisms. Especially photosynthesis and energy molecules were important. I'd like to go into it a little more, but since it's going to be about synthetic organic chemistry and biochemistry, I am still devising a way to write it. I also explained that the mechanism of heredity, which is the basis of life phenomena, is basically an autocatalytic reaction. However, chemical reactions are reversible. When the feedstock is exhausted, the products are decomposed by the same catalyst and returned to the feedstock. Therefore, after a long period of time, the concentrations of raw materials and products are constant at a certain ratio. This is called chemical equilibrium. Which one is greater depends on the difference in enthalpy and entropy between the raw material and the product. In such a state, it would not acquire the purposiveness of living things.
One of the situations in which chemical reactions acquire the mechanism of life is flow. The situation is that the raw material continues to be supplied by the stream and the product is carried away by the stream. Organisms with limited volume take up nutrients and discard waste products. In addition, the raw material is taken into the cell and adjusted so that the concentration of the product does not increase by a continuous processing line. Such a state is called a non-equilibrium state. Since biopolymers have higher enthalpy and lower entropy than raw materials, energy is required to generate biopolymers.
Let us add a flow requirement to the simplest organism hypothesis. One DNA with two genes and two enzymes must be co-located. Amino acids and nucleotides, which are the raw materials, are supplied along with the flow. Amino acids and nucleotides have lower enthalpy and higher entropy than DNA and enzymes, so energy is required to make DNA and enzymes. Then, a mechanism for supplying energy is required. It was introduced that the energy currency of organisms is ATP. Thus, we need an enzyme that supplies ATP, and we also need a scaffolding protein to keep the DNA and the enzymes in place. Just by conducting thought experiments on the simplest organisms like this, the number of essential genes and proteins increases steadily.
The story to the birth of a cell needs a hypothesis that can explain this process well. By the way, in today's organisms, a protein is synthesized by a complex consisting of dozens of RNA molecules and enzymes, and DNA replicase is composed of several types of core enzymes and proteins with dozens of auxiliary functions. Modern sophisticated enzyme complexes are thought to have evolved after the birth of the simplest genetic mechanism.
The birthplace of life requires a constant flow of energy and molecules. Typical examples of energy flows are sunlight and hydrothermal vents on the ocean floor. Molecular flow necessarily depends on water flow. Therefore, the most influential place for the birth of life is hydrothermal vents on the seafloor. Surface water system is unlikely. This is because, in the ancient times, there was almost no surface on the Earth, and organic matters were decomposed especially by ultraviolet rays, pouring down on the Earth.
The flow of water also washes away the autocatalytic enzymes appeared by chemical evolution. The autocatalytic enzyme must then be bound to some surface. The story emerges that autocatalytic enzymes were born from clumps of organic matter bound to the surface of rocks, and that they combined to develop into living organisms.
Four billion years ago, the ocean was saturated with carbon dioxide and was acidic. At the Lost City hydrothermal vent, peridotite was hydrothermally decomposed into serpentinite, and methane was produced from carbon dioxide and water. The serpentinite further decomposed into iron oxide and silica, releasing hydrogen and becoming the source of a wide variety of organic compounds. Silica precipitated into microspheres and tubes. Iron, nickel, and sulfur precipitated on the surface of the thin silica film. There was a gradient of proton concentration in and out of the thin wall. The potential difference was the same magnitude seen in modern cells. The pores were like cells made of inorganic matter, with RNA and other macromolecules bound to the inside of the membrane. Since the pores were not closed, the chemicals and energy supplied by the hydrothermal vents accelerated the chemical reactions in the pores. Chemical evolution took place in this space.
Cells are separated from the outside world by cell membranes. Cell membrane is one of basic structures of independent form of life. The membrane component is lipid. There are two types of lipids in the cell membrane of the present organism. One is a phospholipid, which is used by eukaryotic cells and many bacteria. The other is isoprenoid ether, which archaebacteria, especially thermophilic bacteria utilize this type of lipid. The membrane of isoprenoid ether is so hard that the membrane shows moderate fluidity only at high temperature. As to the origin of life, this type of lipid may be its original form.
Isoprenoid ether has ether bond between isoprenoid and glycerol-1-phosphate. Since glycerol-1-phosphate is bound to both ends of two isoprenoids, the length of the isoprenoid determines the thickness of the membrane. Isoprenoid is a polymer of isoprene monomers composed of five carbons. Eight isoprenes are polymerized to reach to the thickness of archaea membrane. It is unknown how isoprene was synthesized on an ancient Earth. Supposing that it became a cellular structure, so it must have been a common organic matter.
In the present living organisms, isoprene is synthesized by decarboxylation and dehydration reaction of mevalonic acid, which is polymerized three acetyl groups on the base of coenzyme A under the catalytic enzyme (mevalonate pathway). Coenzyme A is a molecule based on adenine nucleotides, and isoprene becomes water soluble by added two phosphate groups. Phosphate group is also energy supplier to the molecule. Another pathway is a reaction combining pyruvic acid and glyceraldehyde, involving a number of heterocyclic compounds such as cytidine nucleotide and NAD, through a deoxyxylulose-mediated pathway.
Another lipid, the fatty acid, which is the constituent material of the other cell membrane, is made on the basis of coenzyme A on a complex enzyme (8 proteins in bacteria, a big protein complex in eukaryotic cells).
Since isoprenoid ethers have phosphate groups at both ends, they spontaneously assemble into a sheet in aqueous solution. Initially, cellular elements grew in vesicles surrounded by sponge-like minerals composed of fine silica fragments generated under high temperature and a high pressure, or iron sulfide precipitated in the form of bubbles. The membrane made of isoprenoid ether kept the components in the protobiont cell from diffusing outside, and the element of the protobiont cell was stabilized. As the membrane has many holes, so protobiont can exchange materials through such small holes.
At first, membrane structure was self-assembled, but later, a catalyst should have been born that bound to the two-dimensional membrane, captured isoprenoid ethers, and added them to the two-dimensional membrane. The catalyst could have been either protein or RNA. By chance, a catalytic system that performs the basic reactions of life was incorporated inside the membrane. For example, a catalytic system that produces chemical energy, that replicates RNA, and that produces proteins. Furthermore, when a catalyst system embedded in the membrane which took in and released substances, substance exchange occurred between the inside and the outside.
The isoprenoid ether membrane grew bigger and bigger, and tore to split appropriately. At this time, the aggregate of autocatalytic molecules in the membrane was randomly divided into two. Conversely, the membrane structure fuses when approached enough to push away structural water on the surface. The different catalytic systems encased in the membrane separated and met again. In this process, the number of vesicles with increased ability to synthesize nucleic acids, small molecules, and macromolecules has increased. The protobiont cell thus started.
There is little evidence of chemical evolution of the isoprene synthesis system. Also, current living organisms have a mechanism to produce ATP by chemical osmotic pressure through biomembrane, but its origin is also unknown. Both are essential to consider the origin of the cell, but at present there seems to be no good hypothesis.
Phospholipids making up the cell membranes of living organisms today are a tough barrier to polar and charged molecules. Cells need complex channel or pump proteins in order to exchange molecules with the external environment. Cell membrane had started with isoprenoid ether as a main constituent. After that, protobionts invented a membrane made of phospholipids (fatty acids) then adapted to a lower temperature environment.
LUCA (Last Universal Common Ancestor), a common ancestor of current organisms, is a top-down approach inferred from gene phylogenetic trees. Conversely, there is a bottom-up approach to non-biologically reproducing biological entities from chemical evolution studies. The latter has no symbolic name, but is called here as FLOQES (First Living Organism in Quasi-Equilibrium State) according to the JAMSTEC hypothesis. There would be a time gap between them. Further fossil evidence suggests a common ancestor OFC (Oldest Fossil of Cell). Since LUCA is not always found as a fossil, there would be a time gap from LUCA to OFC.
From the astrobiological schematic, FLOQES is common to the universe, and then LUCA is environment-specific. Environments in which terrestrial life is born include terrestrial planets, terrestrial satellites, aquatic planets, aquatic satellites, and artificial environments.
According to the law of thermodynamics, the Universe has been cooling and the entropy has been increasing. In that process, matter was born as an entity that stored energy, and matters gathered to form a celestial body. The matters can eventually be described as a temporary stagnation of the flow towards equilibrium. A substance undergoes a chemical reaction, turning into a molecule of lower energy state according to the laws of thermodynamics. At that time, the chemical reaction does not follow the shortest route to the equilibrium state, due to the types of molecules involved and the heterogeneity of the environment. Sometimes detours. Creatures have begun to walk as a collection of such detours.
For example, when a precipitate is formed, a process of dissolving the precipitate is necessary to reach an equilibrium state. The precipitation is an example of a detour. When a layer of substance is formed around the precipitate, the precipitate becomes difficult to dissolve. This is also a detour. Given a membrane-enclosed system, an additional detour is provided by the transport and accumulation of material inside the vesicle. An additional detour is born if a chemical change occurs inside the vesicle on the material that prevents it from passing through the membrane. The formation of a cell membrane facilitates the integration of chemical reactions as detours.
As can be seen in the example of fossil fuels existing on the present Earth, it would have occurred in the ancient Earth that large amounts of organic matter precipitated, accumulated and concentrated. However, even though a lot of organic matter existed in one place, it is difficult to think the new life was created from a mere lump of organic matters. The autocatalytic reaction was discussed in the previous section. I also argued that cells with membranes can preserve a set of autocatalytic enzymes.
There is a concept that a protein molecule has a structure composed of an autonomous element of about 10 to 20 amino acids and the remainder that enhances the performance of the autonomous element. Because primordial proteins formed early in chemical evolution are considered to have evolved under high temperature, small and stable autonomous elements were advantageous. Of course, its reaction specificity was lower and its catalysis is slower, than modern enzyme. That is, they are unstable, and error-prone compared to the current enzyme. The existence of autonomous elements themselves can be thought of as a remnant of primitive proteins.
Since primitive organisms had only the minimum genes (enzymes) necessary for life activities, the substrate specificity of the enzyme is thought to be much broader than the present enzyme (recruitment hypothesis of enzyme evolution). In the course of subsequent evolutionary diversity, these genes duplicated and mutated, eventually acquiring stricter substrate specificity than ancestral enzymes, accompanied by a complicated metabolic pathway.
A gradient of redox, temperature, and/or pressure are formed in nature, and molecules flow along the gradient there. A pool is formed where organic matter accumulates in the gradient, and it is roughly covered with a membrane. Imagine that complex organic matters crowded in gaps of a structure such as a filter or a sponge, and soup composed of organic precursors flow in interspace of them. In the primitive ocean, there are numerous vesicles (protocells), like the prototype of Solaris' s sea. There is a living body with a size of macroscopic, which acted as one organism. They would have been the ancestor of the cellular organisms. Many primitive genes, catalytic reactions, anabolic reactions by chemical energy, enzymes were incorporated within them. It is more advantageous to adapt to the changing environment. I call them protobiont organism, FLOQES.
FLOQES were formed at the chimney of the hydrothermal vent and those of the submarine volcano. When by acquiring the ability to synthesize a membrane, a part of the FLOQES torn off and flowed into the sea, which became the prototype of the cell. They were discovered as the OFC.
The Archaean era has started since 3.8 billion years ago.
The birth of the Earth is 4.6 billion years ago. After the late heavy bombardment period, the atmosphere and the sea stabilized since 3.8 billion years ago. The oldest sedimentary rock ever confirmed is those of 3.8 billion years ago. The oldest cell fossil was 3.5 billion years ago. The carbon component (molecular fossil) which seems to be the oldest biological origin was extracted from the stone of 3.8 billion years ago in Greenland.
The oldest fossil of the cell is thought to be a cyanobacterium of 3.5 billion years ago, discovered from the sedimentary rocks of the Pilbara Formation in Western Australia, Fig Tree Group of Transvaal Province, South Africa. The traces of Pilbara microorganisms were contained in the sedimentary rocks formed around the hydrothermal vent in the submarine that existed at depth of 2000 m about 32 to 3.5 billion years ago. It is powerful evidence that hydrothermal vent is one of candidates of origin of life.
A 3.5 billion-year-old geological body in the North Pole area west of Australia. A sedimentary layer overlies the oceanic crust at that time. You can see its cross section. White dikes run in the ocean crust. They are passages of hot water at that time. The silica dissolved in the hot water was precipitating as quartz in the process of mixing with cold seawater and filling the passage. A number of black lines with a thickness of about 10 μm are observed around the dike. It is a substance made of carbon, which has been identified as a microbial fossil 3.5 billion years ago. This microorganism was presumed to be a thermophilic methane bacterium that could fix nitrogen.
Molecular fossils derived from photosynthetic organisms are distinguished by preferentially incorporating carbons with a mass number of 12 over those with 13. The 13C / 12C isotope ratio of biological carbon is smaller than that of inorganic matter. Examination of the isotopic comparison of sulfur in the sea deposit of 3.5 billion years ago found from Australia revealed chemical synthesis using hydrogen sulfide (similar process to photosynthesis).
More direct evidence is extraction of the biomarkers. As a typical case, lipids (steroids), which are main constituents of the cell membrane, remain as molecular fossils as maintaining the molecular structure specific to certain biological lineage. In the verification of molecular fossils, it is estimated that prokaryotes existed 2.7 billion years ago and cyanobacteria also existed 2.7 billion years ago. The steroid, a molecular fossil of 2.7 billion years ago, is one of isoprenoids.
I assume that perhaps incomplete cells appeared 2.7 billion years ago. By assembling a large number of these cells, they produced metabolites, exchanged each other, supplemented and survived. Primitive cells should have formed a population and loosely bound as a community. The new invention of one constituent cell upgraded the ability of the whole community. In the community, each cell unit replicated to increase its size. The community was occasionally broken up, and increased its number.
The first survival competition is thought to have taken place between individuals with different mechanism from modern organisms. Then a common ancestor of protobionts with one mechanism survived (the Last Universal Common Ancestor). However, this is assumption from the modern theory that organisms should be consisted with individual cell. Immediately after the creation of an living organism, although it is partitioned by the cell membrane from external environment, it is unlikely that they have a mechanism (protein = gene) to identify individuals.
Given that the modern cells which have the same gene replication and gene expression mechanism as the current organism was born 3.8 billion years ago, based on the speed of evolution in the last one billion year, mammals (or organisms with the same ability as that) would have been born around three billion years ago. Despite the accumulation of accidental mutations, the evolutionary rate predicted from the modern genetic machinery is high. Of course, there is a possibility that an intellectual life had evolved to human level in the past. But such an intellectual life would have changed the Earth's surface "unnaturally" by its activities, so that its traces would have remain.
According to the RNA world hypothesis, a mechanism has been created to functionally complement the mechanism of gene replication and enzymes. Its basic component is RNA-protein complex such as ribosome. Ribosome of current organisms is a complex composed of 50 kinds of proteins and at least 3 types of RNA molecules. If these structures and functions came up with try and error, it would not seem quite accidental (= spontaneous). Besides that, the splicing device and the RNA virus replication intermediate are also an RNA-protein complex.
It is difficult to imagine that the ingenious mechanism of the living organism was naturally formed. The intelligent design theory, saying that an advanced intelligence created the living organisms, defines such an advanced intelligence as God. The intelligent design theory mentioned a bacteriophage as an example. Certainly, it is hard to believe that advanced molecular machines, bacteriophages were created by accident. However, many bacteriophages were discovered and analyzed, and it can be concluded that bacteriophage, a sophisticated molecular machine, could also evolve as a result of mutations and natural selection. In other words, the evolution is fast if the genetic mechanism is established. Conversely, it is expected that there will be a long history of trial and error until the genetic mechanism is created.
I think that the foundation of a mechanism for functionally complementing the mechanism of gene replication and enzymes in RNA world was completed during about one billion years from 3.8 to 2.5 billion years ago (= beginning of Archean era). We must propose a hypothetical process in which a mechanism to provide proteins with appropriate performance during this one billion year.
My hypothesis is that nucleobases provided proteins. Nucleobases, when moderately cleaved, become oligopeptides. Nucleic acid bases are sequentially arranged on the RNA molecule, making a pair by hydrogen bonding. The heterocycles or nucleobases are cleaved, and bind each other with a nearby nucleobase through reaction energy, so that a somehow large peptide can be formed. Also, there was a suitable catalyst for cleaving the nucleobase (there is no evidence for this reaction). RNA that decomposes to provide the peptide which catalyzes the replication function is advantageous as compared with those replicating by catalytic action of its RNA. RNA that produces peptides that catalyze its own replication will increase in number in the RNA world and should dominate in evolution.
The sequence of the peptide depends on the sequence of the nucleobase. Various peptides were born according to the sequence of RNA. As long as the peptide is not degraded, it accumulates in the system and continues to catalyze the reaction. Peptides complexed with RNA and/or other peptides provided the complex catalytic reactions. Among the peptides, set of molecules that catalyze reactions that provide their own materials prominently progressed and begin to evolve, that is, reactions that synthesize RNA, and thus reactions that provide parts of RNA. The self-proliferating complex molecules and their gene sets are easy to imagine as virus that created replication and translation mechanisms in primitive cells. However, the current virus relies on protein synthesis for ribosomes of its host cells. Whether peptides / RNA complexes responsible for their own synthesis / replication have evolved as generalized functional structures, and established ones were protein synthesis systems containing ribosomes.
By studying the ratio of oxygen isotopes in rocks formed on the ridege 3.2 billion years ago, it is speculated that there was no continent until 3.2 billion years ago. At that time, ridges were formed where the mantle convection flowed, and archipelagos were formed where the plates subducted. A large amount of accretion accumulated on the arcuate archipelago of the plate boundary. Large amounts of accretion accumulated, especially at points where a chain of submarine volcanoes fed from hotspots subducted, causing the surrounding crust to fold and bulge, forming giant islands. Since these islands were mainly composed of relatively light rocks such as granite and andesite, they floated. Thus, the surrounding plates subducted around them. Volcanic activity increased on such plates, forming large landmasses and forming the first cratons. Cratons are stable old continental masses over 500 million years old, composed mainly of granite and estimated to be 200 km thick. The oldest craton is over 2.5 billion years old.
The plate consists of a 100 km thick crust and a 310 km thick upper mantle. A craton is an image of an iceberg floating in the upper mantle. Between the upper and lower mantle is the 250km mantle transition zone. The subducted plate mass floats at a depth of 660 km around the plate. This depth corresponds to the upper surface of the lower mantle. As the Earth cooled, plate clumps began to accumulate above the lower mantle. Plates accumulated under particularly large cratons turned into magma that erupt to the surface, but remains formed a huge cold plume that penetrated the lower mantle and sank onto the core. Cold plumes have caused hot plumes elsewhere to reorganize the Earth's mantle convection. The direction of movement of the plates on the Earth's surface changed, and the arcuate archipelago and land masses on the plates collided, accreted, and coalesced, and eventually a huge continent was born.
A huge mountain range was created by a collision of kratons. The oldest one was about 1.8 billion years old. It is the era of the first supercontinent, called Laurencia (Nuna). The first supercontinent was the combination of the current North American continent with Greenland, the Scandinavian peninsula, the Australian continent, and the eastern Antarctica. The area is estimated to be as large as the North American continent in present days.
Mantle convection induces movement of the plate covering the Earth's surface. Plate motion is directly observed as speed of several millimeters to tens of centimeters in one year using GPS and other technologies. As a speed of roughly 3 cm per one year, a mass was risen up over about 100 million years traveling through 3000 km from the core surface to the surface of the Earth. On the contrary, when a cold plume occurs, it takes about 100 million years for the tip to reach the core, during which 3000 km square plate is drawn. Since the circumference of the Earth is 40,000 kilometers, after the cold plume occurs, roughly 600 million years ago, all the plates gather at the place of the cold plume = an ultra-continent would be formed. Wilson cycle is faster than this calculation.
The first supercontinent was formed at 1.9 billion years ago. These periods showed the highest volcanic activity throughout Earth's history. Volcanic activity created a large amount of magma, which became the base of the continent. During this time, photosynthesis was evolved, which releases oxygen, and cyanobacteria were born. It is estimated that 2.3 billion years ago, global freezing occurred and caused massive extinction of living things. As a result, it appears that eukaryotes appeared 2.1 billion years ago. In the African continent and its surroundings, small continent collisions occurred 2, 1.1, and 0.7 billion years ago, and gradually grew to a larger continent. The last collision shaped southern Africa and is called the Damara Orogeny.
Virus has been thought to originate from fragments of genes escaping from cells. However, when phylogenetic trees are constructed by comparing DNA or RNA replicases, the viral enzymes are located outside the three domains of eukaryotic cells, archaebacteria, and eubacteria. Therefore, it seems that there would have been many types of nucleic acid replication enzymes, as typified by viruses, before cells were organized into three types. The age is unknown because an accurate evolutional clock cannot be made, which demonstrates a longer history of its origin.
Mammalian and plant viruses have only the genes of protein capsules housing its nucleic acids, the genes required for nucleic acid replication, and the genes needed to parasitize cells. The smallest virus has only three genes, whereas the largest one has about 100 genes. Viruses rely on ribosomes for protein synthesis. After the ribosome evolved as a device for synthesizing proteins, the virus would have been established as replicating organisms and would have begun its own evolution. Viruses were the inhabitants of the RNA world.
Viruses have all combinations of replication enzyme of the gene, one that replicates RNA using RNA as a template, one that replicates DNA using DNA as a template, and synthesizes DNA using RNA as a template. Cells commonly have enzymes that synthesize RNA using DNA as a template. Since the first replicable molecule is expected to be RNA, organisms that have RNA as genomes should also contain viruses.
Virus propagation is just a chain of events. That is, the process of its proliferation is written into its genes step by step. Cells have material fertility that can support the growth of the virus. Before the birth of the virus, that is, before the formation of cells, there must have been an environment with sufficient material abundance to allow the virus to survive. In addition, the virus must have carried out activities to create an environment favorable to its survival. The big fruit might have been a cell. When exposed to competition with cells, the virus armed with its small genome size by replicating quickly and having a high evolution rate.
The virus evolved RNA dependent DNA synthetase (reverse transcriptase). And at that time, there is a possibility that viruses took over the replication mechanism of the cell that had used RNA as a gene (From the cell's point of view, the cell uses the virus to convert its own genome into DNA). Given that this hypothesis is correct, the DNA-ization of genome was before cells divide into three domains. Poxviruses create a membrane-covered structure in the cytoplasm, replicate in it, and synthesize mRNA. This function is equivalent to the cell nucleus. The nucleus of a eukaryotic cell might be derived from a giant virus such as a poxvirus.
Among viruses infecting protozoa, there are viruses with genomes of a size comparable to small bacteria. The giant virus develops nucleoid in the cytoplasm of infected cells like a poxvirus. These giant viruses contained metabolic enzymes (viruses do not metabolize) and genes for biosynthesis. Comparing these genes with eukaryotic cells and bacteria, the branch time was estimated to go back at least 2.7 billion years ago. However, since it is also presumed that the large virus had taken up the host cell gene, estimation of the origin needs further examination.
From the study of bacterial viruses (bacteriophage) it was known in the 1970 's that viruses was able to take fragments of genes when they infect cells, then they were able to bring the fragments into the infected cells. In mammals it is thought that retroviruses have played a role in carrying genes. Also, the virus replicates in the genome and 20% of the mammalian genome is presumed to be derived from the virus. Those gene fragments are not functioning. In some cases, the fragments derived from viral genes have functioned and assumed to contribute to evolution of host organism.
Focusing on genes shared by all living organisms and measuring their molecular evolution, we can calculate the time when the first organisms were born. Nucleotide sequence of ribosomal RNA was examined first. Ribosome is a protein-synthesizing machine universally possessed by cells, is well conserved, and contains RNAs as a constituent. Ribosomal RNA is also encoded in a genome DNA.
The oldest organism in the phylogenetic tree made from the nucleotide sequence of ribosomal RNA is the prokaryote, yet it is the eubactrium. Archaebacteria branched about 1.8 billion years ago. The archaebacteria grow in extreme environment; halobacteria in high salt water, acidophilic bacteria living in extreme acidic environment, and thermophilic bacteria adapted at high temperature of 100 C. Subsequently, eukaryotes emerged from this group 1.5 billion years ago, when the simple cellular structure of prokaryotes changed to complex eukaryotic cells. A part of proteins (genes) of eukaryotes, of mitochondria and lysosomes are derived from eubacteria.
However, when using another gene, the archaebacteria come to the root. The phylogenetic trees that the eubacteria are close to the primordial organism are provisional. Not the individual genes but the results of the analysis of the entire genome ongoing to be analyzed now will give a surprised result. In any case, prokaryotes are organisms that make up the majority of the molecular phylogenetic tree, and other animals and plants are only one of the small branches. Biochemical diversity in prokaryotes is the most prominent.
Regardless of archaebacteria or eubacteria, the root organism of the phylogenetic tree is a thermophilic bacterium. Life began at the hot bottom of the ocean, and it is thought that it divided into archaebacterium and eubacterium under hot environment.
Deduced from molecular phylogenetic tree techniques, and restored proteins experimentally, ancestral proteins were more heat resistant. Therefore, it was suggested that the ancient life inhabited under the high temperature environment. Furthermore, when estimating the ancestral type of elongation factor proteins of more than 25 kinds, they were highly thermostable. The circumstance of ancient life was suggested that the temperature gradually decreased by 30 C until 500 million years ago.
Of the 4288 genes found in the E. coli K12 strain, there are only 303 genes necessary to grow in synthetic medium in the laboratory. Also, if you classify genes from their functions and sequence similarity, universal genes will be 200. Because there are extinct genes, it is estimated that 1000-1500 genes were worked at the time when an independent living organism was established.
Researchers from Denmark University reported an analysis of 61 E. coli genomes in 2010. The pangenome of E. coli contained 15,741 genes, with only 993 core genomes (6%). From these results, it was found that E. coli also obtained genes by horizontal gene transfer from microorganisms distantly separated in phylogeny.
In addition, researchers at the University of Dusseldorf compared the 537,923 genes in 181 prokaryotic genomes and examined the horizontal movement of genes. As a result, 80% of the genes were thought to be moving horizontally. Therefore, the phylogenetic trees of bacteria were considered to be in the form of a mesh or a net considering of vertical transmission and horizontal shift of genes.
When we placed the energy acquisition method for carbon dioxide assimilation onto the evolutionary phylogenetic tree made from the ribosomal RNA genes, what appears first is photosynthetic bacteria that do not generate oxygen. Photosynthesis has two reaction center complexes, type I and type II, but the early bacteria have only one of them. Cyanobacteria have both photosynthetic reaction centers and appeared later. Cyanobacteria are gram-negative eubacteria. Among Gram-negative bacteria, the branch point of cyanobacteria is quite old in the phylogenic tree. Since cyanobacteria are the first organisms that have a powerful photosynthetic mechanism, it is speculated that they boasted overwhelming proliferation power. Even today, there are many species of cyanobacteria, their habitat environment is vast and have symbiotic relationship with various organisms.
Cyanobacteria generated a large amount of oxygen. While oxygen is a highly toxic substance for living organisms, energy can be efficiently extracted by using oxygen. In principle, this process is to rotate only inversely the photosynthesis circuit (catalyzes reverse reaction). Aerobic bacteria performing oxygen respiration also evolved. They were possibly cyanobacteria that lost photosynthetic ability or bacteria coexisting with cyanobacteria.
After 2.7 billion years ago, the area of the shallow sea also increased during lands were gathered. The attack of energetic particles from space was also prevented by the geomagnetic umbrella. Environmental conditions were developed for photosynthesis bacteria that had progressed to near the sea surface can prosper in full swing. Traces of the prosperity of the cyanobacteria which is photosynthetic bacteria of this time are left in sedimentary rocks as stromatolite fossils.
Cyanobacteria still live in various environments around the world. Cyanobacteria, like ordinary plants, have chlorophyll, which diffuses in the cell without being packed within the chloroplast. Some species live alone, but most of cyanobacteria form colonies and filaments. Cyanobacteria releases greasy glycocalix and sticks sand grains etc. in the sea. Cyanobacteria cells divide on the surface of the accumulated sands and increase its number. And they put sand grains on top of them. Thus, the sand grains accumulated over a long period of time which reflects the seasons and climate change. Thus, stromatolites have a streak pattern as annual rings.
On the outermost side of the stromatolite is a membrane of cyanobacteria, and another kind of bacteria settles inside it. It seems to be in symbiosis symbiotic relationship. The basic relationship has not changed for 2.7 billion years. Stromatolite attracted other bacteria to create ecosystems and provided a foundation for the evolution of eukaryotes. Stromatolite began its peak in 2 billion years ago.
Due to the prosperity of photosynthetic organisms like mainly cyanobacteria, the biomass had increased far more than ever. Furthermore, the supply of organic molecules and the route of material circulation in the ecosystem also changed. Biological production was mainly done in shallow ocean and oceanic surface layers, and the products deposited onto the ocean floor. Biopolymers of high molecular weight were supplied to the whole ocean, and the biosphere expanded not only to the oceanic surface but also to the ocean floor. In the ocean floor up to that time, only several biospheres were found around the hot water circulation system. A large amount of carbon was fixed and added to the ecosystem. This vast amount of organic matter would guarantee the evolution since then.
In the Proterozoic era, stromatolite became to be peaked in 1 billion years ago, and fell to one-fifth of its peak in the Cambrian era.
Cyanobacteria produced oxygen from carbon dioxide in water by photosynthesis. Oxygen bound with iron ions in the seawater and precipitated as iron oxide. The banded iron formation layer that human beings use today as the major iron source deposited in this way 2.6 to 1.8 billion years ago. Oxygen concentration in the atmosphere increased to the level of about 1% from 2.5 billion to 500 million years ago. As oxygen was constantly supplied, organisms breathing oxygen evolved.
Oxygen is poisonous to living things because of its strong oxidizing action. Reactive oxygens, which are generated by decomposition of oxygen molecules by ultraviolet rays or so, reacts chemically with every molecule to destroy them, such as ones constituting the cell. Living organisms developed enzymes resistant to oxygen, such as super oxide dismutase, catalase, peroxidase, etc., and acquired tolerance to oxygen by equipping these enzymes in the body.
As the living organisms obtained resistance to oxygen, then they could utilize oxygen. They created a respiration system to synthesize ATP, which is the energy molecule. Aerobic respiration using oxygen can produce energy about 19 times efficiently compared with anaerobic respiration (fermentation). Thus, in aerobic conditions, living organisms breathing oxygen became a mainstream of living organisms, supporting appearance and evolution of advanced lives.
Oxygenation of the Earth's atmosphere is thought to have progressed in two stages, near the beginning and the end of the Proterozoic (about 2.5 billion years ago and 550 million years ago). However, it is not well understood that the ocean oxidation state in this stage and the time when oxygenation took place in the deep ocean.
This is my speculation that oxygen generated by photosynthesis may have oxidized metal ions in the sea and precipitated them as minerals. It is estimated that the Proterozoic sea salinity is five times higher than it is today. The salinity of seawater gradually decreased from 1 billion years ago, and reached the same value as it is today 600 million years ago. There is also a theory that the decrease in salt concentration in seawater is due to the increase in land area and sequestration of salt inside the continent as rock.
The plate contains seawater during its formation and movement to the subduction zone. After the plate subducts into the mantle, heat and pressure separate the water from the plate. However, between 100-600 million years ago, water was no longer completely separated from the plate. In other words, it can be said that the Earth has cooled down that much. As a result, seawater was injected into the mantle, leaving less water and slowly increasing the land area.
Rivers flowed on land, and sediments were transported to the sea by rivers and became sedimentary rocks. Organic matter produced by living organisms on the seafloor was trapped in sedimentary rocks and was therefore not oxidized. 600-500 million years ago, the oxygen concentration in the atmosphere increased. Higher oxygen levels allowed organisms to maintain larger bodies because they could obtain energy more efficiently through oxygen respiration. Anaerobic organisms that had been found everywhere on the Earth were relegated to environments with little oxygen, such as deepth in soil.
Unicellular organisms are constantly exposed to the outside world. In even single cell, sensors were evolved to know the state of the outside world, for surviving in the harsh environment. First is the water temperature which is a physical stimulus. Cells born in a high temperature environment could not survive at low temperature. Next is a light sensor. Cyanobacteria that feel light to favor photosynthesis were advantageous for survival. As for a chemical signal, they are pH, concentration of various substances and ions. Bacteria sense them as food and also sense substances produced by fellows and other microorganisms.
The sensor of bacteria is called a two-component system, which consists of two components, a receptor protein (detector) and a regulatory protein (output device). For example, E. coli has 26 receptor proteins and 36 control proteins (includes putative ones).
It is the protein that constitutes the receptor and sensor. The protein is consisted with 20 kinds of amino acids linearly linked, and the type and order of amino acid are encoded as genetic information. Protein molecules are sterically folded according to the properties of amino acids and adopt a specific structure in aqueous solution. If the protein comes into contact with other molecules, binding occurs and if it matches the moieties of amino acids at that site, the binding is further strengthened and causes structural changes of the protein (allosteric effect). As a result, the protein is activated. For example, binding to specific low molecules is strengthened, exerts enzyme activity, and interaction with other proteins are created. If binding remains at a low level, the protein will not be activated. Proteins interact only with specific partners.
The receptor protein bound to the target substance in the outside causes its structural change and phosphorylates the regulatory protein. Phosphorylation is enzymatic activity. The regulatory protein is usually a phosphorylated protein, which phosphorylates several proteins in the cell and informs other proteins in the cell of the presence of the external substance. With this repetition, the cells activate the sleeping genes, activate the respiratory reaction, produce energy, and enter the dormancy regime as spores if necessary. In some cases, cells are committed suicide (apoptosis). If it is a eukaryotic cell, it causes to activate phagocytosis, to change membrane transport and the delivery destination of the protein. These activities change the whole cell to respond to changes. If the change in the external world is important for survival, cells change dramatically.
When the organic molecules and oxygen were stably supplied by photosynthesis, it seems that the living world has changed largely in its structure. One of them is diversification through symbiosis. It is thought that archaebacteria swallowed aerobic bacteria and cyanobacteria and began cohabiting, then changed into the organelles, mitochondria and chloroplasts, respectively, enveloped by double membranes (Maggius’s intracellular symbiosis theory).
Bacteria have been found in rocks under the sea floor and in groundwater in deep. Such bacteria that live in environments that are largely free of organic molecules are believed to have grown and divided once in over hundreds to thousands of years. They live in the strata which may have formed tens of millions of years ago. These bacteria are even estimated to account for 70% of the Earth's bacteria. Since these bacteria cannot be artificially cultured, metagenomic analysis has been performed.
Lokiarchaeota, which was first discovered in 2010 in the mud on the seabed of Greenland, was classified as an archaea and named Asgard as the archaeal phylum. Lokiarchaeota has several genes that are similar to those found only in eukaryotes. For example, actin, which is a major protein in skeletal muscle. Some proteins involved in the secretion of proteins and substances. The archaeal candidate that swallowed eubacteria is considered to be Lokiarchaeota. Eukaryotes are located on archaeal branches (eocyte theory).
Bacterial evolutionary clocks become a group at some point, reflecting crosses each other. Prokaryotic DNA is considered to be free to cross when the cells are fused because the DNA is naked inside the cell. Therefore, the phylogenic tree becomes complexly merged or ring-shaped, so that the origin of life cannot converge into one genome.
Throughout the history of the Earth, the volcanic activity was the highest around 2.7 and 1.9 billion years ago. Volcanic activity produced a large amount of magma and became the foundation of the continent. About 2.0 billion years ago, the temperature of the Earth's crust and the outside layer of mantle declined enough to keep water along with subducted oceanic crust. As a result, massive amounts of granitic rocks were made on the subduction zone. A homogeneous and hard graniteous continental land mass was formed in a short period. A giant continent was formed in 1.9 billion years ago for the first time. Continental growth can be explained as the heat release mechanism from inside the Earth.
The continental fragment stabilized before the Cambrian period is called craton. The oldest ones among cratons have existed before 1.8 billion years ago. It is just the age when the first giant continent was formed. When the supercontinent is formed, small lumps, derived from the volcanoes along the plate subduction zone that had been formed over from about 4 to 2 billion years ago, were considered to be collected and stacked up.
There was Nuna (Laurencia) giant continent 1.75 billion years ago, followed by the formation of the Columbia supercontinent 1.5 billion years ago. Next was the Umkondia giant continent 1.11 billion years ago, followed by the Rodinia supercontinent 900 million years ago. There was the Gondwana giant continent 520 million years ago, and the Pangea supercontinent was formed 300 million years ago. There is now the Eurasian giant continent. Approximately 200 million years later from now, the Amasia supercontinent is expected to form. The giant continent gathered the surrounding continents to become a supercontinent in about 200 million years. It is called the Wilson Cycle, which has a period of about 600 million years, during which changes in the number of continents, changes in sea level, development of glaciers, and mass extinctions of organisms occurred. All of these have caused organisms to evolve.
Nuna continent would be reconstituted by connecting traces of the old mountains (now plains). It formed from North America, Greenland and Northern Europe. Other land areas in that era were southern Siberia, East Asia, Antarctica, Australia, Africa, South America, India, and small areas around the Black Sea and the Caspian Sea (all are fragments). More than 1.5 billion years ago, the thickness of the oceanic crust was more than 15 km. However, after 1.5 billion years ago, it has become as thin as 5 km. The formation of the Columbia supercontinent wiped out the old oceanic crust.
The largest meteorite crater in Earth's history is the Vredefort Collision Structure (South Africa, 300 km diameter) about 2 billion years ago, and follows by the Sudbury Collision Structure, 1.85 billion years ago (Canada, 250 km diameter). These Meteor Craters can be preserved because the continental mass was formed for the first time in Proterozoic era. On the other hand, the Chicxulub crater that destroyed dinosaurs is 180 km in diameter.
The Rodinia continent is thought to form by gathering most of continental lumps, mainly on the south side of the equator about 1.1 billion years ago. The Glenville orogenic movement occurred due to the collision of the continents to form the Rodinia. The continent started to divide 750 million years ago.
As the temperature of the Earth cooled down, it is thought that the top of the hot plume had gradually moved deeper under the crust. Currently it works only at the level deeper than 670 km. This depth is also the depth of megalith is made. The depth should have been shallower in the more past. While the Earth was hot, the seawater entered into the plate as hydrous mineral was separated by heat and returned to the ground. However, as the Earth cooled down, water ceased to be separated and it remained in the mantle as a hydrous mineral. This is called injection of seawater into the mantle. It started 1000 to 600 million years ago, and sea water has decreased to two-thirds so far. Land increased from 5% to 30%. With the advent of the Gondwana supercontinent, a huge continent emerged for the first time on Earth.
The supercontinent Pangea formed 320 million years ago and broke apart 175 million years ago. After the Pangea supercontinent split, the Pacific Ring of Fire formed. The present-day Pacific Ring of Fire roughly follows a line that cuts the earth in a plane. There are mantle upwellings on both sides of the face (under the South Pacific and African continents). The Eurasian Continent moves northward along the Pacific Ring of Fire and collides with the Amelia Continent, which is the union of the North and South American Continents, forming the next supercontinent, Amasia. Antarctica does not appear to be included in the Amasia continent.
Carbon dioxide in the atmosphere has been rapidly consumed as the continent has grown rapidly since the 2.7 billion years ago, and the global environment has evolved into an environment similar to the present condition for about 1 billion years ago. As continents were formed, the rocks weathered and were brought to the sea. Alkali metal ions contained in rocks were dissolved to the seawater, where carbon dioxide was absorbed to neutralize these ions. Furthermore, in the dividing and gathering phase of continents, a shallow sea spread out between them and cyanobacteria propagated there, photosynthesis lowered the concentration of carbon dioxide in the atmosphere. As the concentration of carbon dioxide in atmosphere decreased, atmospheric pressure also decreased.
The sun was darker as it went back to the past, and the average temperature of the Earth about 2 billion years ago was assumed below zero. Then the Earth should have been frozen globally before 2 billion years ago. However, there are evidences in sedimentary rocks which shows not to be frozen. We call this ‘faint young sun paradox’. Carbon dioxide is a powerful candidate as an atmospheric component explaining the paradox. The Earth, which lost the greenhouse effect of carbon dioxide, has experienced three global freezing.
The first global freeze (Snowball Earth) occurred 2.22 billion years ago. It's called the McNigan Ice Age. There were two Snowball Earths 730-630 million years ago. Also known as the Sturtian and the Marinoan Ice Age. The Earth may have frozen several times before this. It may have been covered with icebergs, if not the entire globe. Moderate level of icebergs may have protected photosynthetic organisms such as cyanobacteria from ultraviolet radiation.
There are mainly two evidences of freezing at the equatorial zone. One is diamitite. When glaciers scrape and transport the bedrock, sediments called diamitites are formed in which gravel, sand and mud coexist. At this time, the gravel remains after the glacier has been scraped off. The second one is dropstone. Mud and fine sand at the bottom of the sea deposit far offshore. If there is big gravel stuck there, we call it dropstone. Dropstone is thought to have been brought by the iceberg.
If the Earth's surface is completely covered with ice, the most living organisms are thought to have extinct, due to separating from the air and sunshaine. However, it is known that cyanobacteria survive even on the surface of glaciers, making stromatolite-like structures. It is known that insects and bacteria can live even on ice. Also, at the active place of volcanic activity, where would have been not completely frozen, some living organisms could survive. The Snowball Earth epoch seems to be linked to biological evolution. Cyanobacteria prospered after the McNigann glacial period (2.22 billion years ago), and multicellular organisms emerged and evolved after the Sturtian and Marinoan glacial periods (730-630 million years ago). When we create an evolutionary phylogenetic tree of the basic gene groups necessary to construct multicellular organisms, the root of the phylogenetic tree is at this period.
It is estimated that the temperature has reached -50 C during Starcian Snowball Earth of 730 million years ago. However, due to balance with crustal heat, the seawater at the bottom of the ocean did not freeze. While the speed of photosynthesis is decreasing during global freezing, on the other hand, supply of carbon dioxide was made by volcanic activity continuously, greenhouse gases are accumulated and the temperature started to rise. It takes at least 4 million years to accumulate in the atmosphere the amount of carbon dioxide necessary to melt the entire ice of the Earth. Once thawing of the ice bergs, the albedo effect decreases, so deicing progresses further. Rapid warming caused storms and floods. After a while, the high temperature period continued for a while.
Reductive substances are supplied from the seabed hydrothermal vent, so oxygen dissolved in the seawater is considered to be exhausted during snowball Earth. Under such an oxygen-poor environment, divalent iron ions supplied from the seabed hydrothermal vent can be dissolved. A large amount of iron ions accumulated in the seawater at deep ocean over a long period of Snowball Earth to the onset of ice melting.
Current eukaryotic cells are not simple symbiosis, because the entire genome is a hybrid of genes from archaebacteria and genes from eubacteria. When roughly divided, the information gene group that translates DNA information into protein is derived from archaebacteria and the other functional gene group is derived from eubacteria. On the other hand, ribosomal RNA sequences are divided into eukaryotes, eubacteria and archaebacteria. Estimation by the evolutionary clock of the ribosome gene, eukaryotic organisms were born about 1.5 billion years ago. The hypothesis on the origin of eukaryotes is the symbiosis theory proposed by Ms. Margilus in 1967.
The first eukaryotic cell fossils are found 100 million years (2.1 billion years ago) from the first Snowball Earth. Grypania appeared 2.1 billion years ago. It was found in Banded Iron Formation (BIF) in the United States. It is considered to be a eukaryote because it is a large alga with a size of about a few millimeters and cannot be this size in prokaryotes. Schizon is one of unicellular algae with the most primitive structure among plants. It is a kind of red algae, it lives even in a strongly acidic, high temperature environment (hot spring). Schizon has every intracellular organ of eukaryotic organism, but there is only one. It is the simplest structure as a plant. Therefore, it is noticed as an ancestor of plants. The cell nucleus contains 20 chromosomes and the genome size is 16,520,305 base pairs. There are 5,531 genes, almost the same number as yeast and malaria parasites which are eukaryotes of single cells whose genome has already been determined. Its mitochondrion has a genome of 32,211 base pairs, and chloroplast has of 149,987 base pairs. Chloroplast genome size was minimal in plants.
Algae are regarded as primitive plants. It is classified into 10 eukaryotic plant divisions, which are greatly different in cell structure and function, and cyanobacteria which are prokaryotic algae. It is thought that algae could be formed through multiple intracellular symbiosis of organisms of different origins. Chloroplasts are thought to be cyanobacteria, which have changed by intracellular symbiosis. The chloroplast looks like a wrapped Cyanobacteria with the membrane of the maternal cell. That is, the chloroplast has two cell membranes. This is the primary intracellular symbiosis. Green plants, red seaweed plants and gray plants commonly found in three primary phyla are symbiotic form in the primary intracellular symbiosis, which are the major of the current plant world.
There are algae with three or more chloroplast envelopes. These algae are born from the secondary intracellular symbiotic plants. It is thought that the first intracellular symbiotic plants have entered other cells and cohabited. Algae that acquired chloroplasts by secondary intracellular symbiosis are regarded as the sixth field independent of the plant kingdom, the chromista world. As a side note, the remaining five are the Monela world (Prokaryote), Protozoic world, Plant world, Fungus world, Animal kingdom.
Cellular organs have evolved that maintain and utilize diverse membranes. For example, a space wrapped by membranes is utilized to create a concentration gradient by enzyme reaction in the membrane. Proteins developed that convert the potential energy through concentration gradient into chemical energy, ATP. In current organisms, most of the ATP is supplied by a concentration gradient (chemical osmotic theory). Typical examples of intracellular organisms that efficiently produce concentration gradients are the mitochondria responsible for respiration and chloroplasts responsible for photosynthesis. Also, there are lysosomes and phagosomes that trap substances that become unnecessary in cells and substances taken from extracellularly, respectively, into membrane bags (vesicles) and digest them. Proteins that are secreted outside the cell are synthesized in the endoplasmic reticulum and processed and modified through the Golgi apparatus, all of which proceed by providing a special reaction field by vesicles.
Eukaryotic cells have not only increased volume, but also evolved important intracellular movement organs, such as cell division machinery, in addition to membranous organs. The mechanism that made the primitive eukaryote has created more complicated intracellular symbiotic organisms. Furthermore, it is possible that more combination was made, and it seems that many gigantic cells may have appeared that are not currently present. It is thought that its driving force was efficient energy production and substance production realized by division of intracellular labor and specialization. Also, energy-efficient oxygen respiration will support the birth and evolution of advanced organisms.
Among parasitic microorganisms, there are creatures living by getting into cells. Shigella and other bacteria attach to the intestinal cells, inject proteins into the cells to acceptable the bacteria, and let them take in. The intracellular bacteria hide from the digestive system and intestinal immune system, and can grow in small intestine cells.
Malaria parasite is a unicellular eukaryotic cell organism. When infected in living organisms, malaria first grows in hepatocyte then lurks in erythrocytes. Malaria produces parasitic membranes in the red blood cells and is enveloped in the membranes. The malaria parasite secretes various proteins, disintegrates parasitic membranes, and sends proteins to the whole erythrocytes. The processed erythrocyte escapes to the host's immune function. Molecular mechanisms of malaria that enter and control the red blood cell are now a major research field. The mechanism would have been evolved over several hundred million years before multicellular organisms were appeared on the earth.
Cells started with intracellular parasitism, then their forms progressed complicated and diversified. Their abilities have been refined. Microorganisms have emerged that live in the cells while maintaining independence. For example, Shigella and the like bacteria attach to the intestinal cells, inject the protein into the cells, and make themselves take in. It grows in cells hiding from host digestive system and immune system. The malaria parasite is hidden in red blood cells, wrapped in a parasitic membrane. The processed erythrocyte escapes to the host's immune function. The basis of the molecular mechanism of entering and controlling the cells may have been evolved over several hundred million years before multicellular organisms were formed.
The symbiotic theory assumes that phagocytosis is the initiation mechanism for symbiosis, but it can be generalized more. That is, some archaebacteria developed long protrusions to increase their surface area. Other bacteria sometimes settled between the projections, and they had a symbiotic relationship. The archaeal membrane swelled and fused on the outside, and also fused on the inside. As a result, the inner membrane became the nuclear membrane and the outer membrane became the cell membrane. The bacteria that had been engulfed in the meantime evolved into mitochondria. The mechanisms of long process formation and membrane fusion are prototypical dynamics of eukaryotic membrane structures. A candidate for symbiosis is Asgard, which has long spaghetti-like projections from a core-like center.
Animals and fungi are evolutionarily closely related organisms, and both belong to the group called opisthokonta, which originated from organisms with flagella behind their cells. The traces are very similar to mammalian sperm and spores (zoospores) of the most primitive fungi, the phylum Chytridiomycota. They are also heterotrophs.
A eukaryotic cell was born and the mechanism of sexual reproduction was arranged.
The gene replication device is not 100% perfect. Replicating devices of the current living organisms make mistakes with a probability of about 1 / 10,000,000. Mutation accumulates gradually as a genome duplicates and divides into two. Eventually, the organism dies when a fatal mutation occurs. Even more deadly, before the ozone layer was formed, a large amount of ultraviolet rays were falling on the Earth 600 million years ago, and the ground and the sea surface were a death world for organisms where genes made of nucleic acids were destroyed away.
Bacteria just born on the Earth developed a mechanism of exchange their genes each other to repair genes broken by ultraviolet rays. Since the birth, bacteria formed aggregates and lived together, which has become a driving force to have the recombination mechanism. Conversely, having a gene exchange system was essential for stabilizing and perpetuating species. It also became a defense mechanism against accidental mutations.
When the environment got worse, the ability to exchange genes was demonstrated to be highly active. Bacteria gathered together, made dead friend food, sometimes cannibalized and survived in a difficult environment. It is assumed that they provide their genes to fellows to survive. It is also assumed that intracellular symbiosis has been born in this process.
When bacteria started to live as individuals, the mechanism of gene exchange was established as a conjugation. Bacterial cells recognize each other, bind, and form a tube between each cell to convey the DNAs. After that, the genome of one bacterium is duplicated and sent to the other. Transferred DNA is recombined mainly with homologous parts and exchanged. At this time, it is irrelevant whether the homologous part is broken. The gene set of genes necessary for conjugation is carried by the carrier genes called plasmids. Plasmids are maintained in the bacterial population by carrying genes useful for the survival of bacteria such as antibiotic resistance and phage resistance.
When a nucleus, which is an intracellular organ that stores genes, was born, the whole gene exchange has been carried out regularly with the nucleus as a unit. It is the birth of eukaryotes. First, two sets of genes necessary for life (genome) were prepared. In fungi (eukaryotic cells, not eubacteria), one genome is usual (haploid) when proliferating by cell division. Only when they perform sexual reproduction, they stick (join) and exchange a set of genes, that is, exchange of one of the genomes. Two sets of genomes in the participant cells are randomly exchanged with homologous portions of genetic information. The new genomes are separated into two spores, which will be the next generation. Various forms of exchanging genomes may have been tried in ancient era.
A feature of the eukaryotic genome is the intron sequences inserted into the genome. Intron invasion would have occurred around the birth of the eukaryotic cell. At the early stage of the symbiosis, the engulfed bacteria died and their DNA was released into the cytoplasm. A part of the gene was incorporated randomly into the genome of the primitive eukaryotic cells. Beneficial genes were lost from mitochondria because they were maintained in the host genome. The junk DNA was inserted into the gene as an intron. The splicing machinery was developed to remove the introns, otherwise the gene would not function. At the same time, the nuclear envelope was formed to separate unspliced RNA from the ribosomes.
Sexual reproduction, one method of proliferation of eukaryotic cells, consists of two processes: conjugation (fertilization) and meiosis. In conjugation, two haploid cells can be fused together not only to the cell membrane and cytoplasm but also to the nucleus into diploid cells. In meiosis, four haploid cells are generated from one diploid cell through homologous chromosome pairing and two steps of mitosis after the genome replicates to 4 sets in a cell. It is estimated that the sexual reproduction mechanism was established about 1 billion years ago.
Even in sexual reproduction of the simplest fungus, the mechanism is complicated. Many proteins collaborate to do this process. Replication of genes uses an existing mechanism, but even if genes are duplicated, they are not divided into daughter cells, so new control functions are necessary other than mitosis. Also, the new control function must be programmed to only activate during sexual reproduction. Until the sexual reproduction mechanism is completed, many evolutionary genes were born, and their invocation program would have been reworked. The advanced equipment of modern organisms is the result of continuous improvement of the mechanism. The body of higher organisms is based on diploid cells and produces haploid cells (sperms and eggs) only when sexually reproducing.
At the same time, sexual reproduction accelerated the evolution by periodically exchanging genes. Especially when the genome size becomes large, gene exchange by sexual reproduction is effective.
It is difficult to describe 4-dimensionally of changes in living organisms including time such as development, growth and aging. Large multicellular organisms are too complex, and various researches have been done to describe everything from the nucleotide sequence of genes, which is one-dimensional information, to a stereoscopic three-dimensional structure (From 1D to 3D) in terms of molecules. In principle, lines are made by points side by side, a surface is made by lines, a surface is bent to become three-dimensional structure. Also, the line forms a helix to form three-dimensional structure. Whether it is a polypeptide chain or a structure formed by a protein, the same principle is used for the organization of tissues and organs by cells. And genome has evolved little by little through mutation for these changes and has been selected naturally.
Specific genes in the multicellular organism such as genes related to nerve or cell adhesion can be found in the monocellular protozoan Monosiga ovata. Genes necessary for becoming multicellular organisms were already prepared for single cell organism era. When multicellular organisms become involved, the receptor protein for detection of the outside world of the cells and the regulatory proteins linked thereto are remarkably increased. Genes related to cell differentiation such as homeobox gene family diversified 800 to 600 million years ago. The homeobox gene is a regulatory gene that controls morphogenesis in the process of multicellular animal development. It seems that the homeobox gene family, responsible for the body plan and the interaction such as cell adhesion, and related genes, responsible for intercellular information, diversified through gene duplication, and enhanced the function of the organism.
When harmful genetic mutation occurs, the protein is incorrectly folded. As a countermeasure there is a group of heat shock proteins. The heat shock protein plays roles that correct the denatured protein to the correct shape and must have evolved as a protein group corresponding to the sudden temperature change. Organisms can accumulate much genetic diversity depending on the ability of heat shock proteins. This hypothesis was demonstrated by experiments in Drosophila. Drosophila accumulates many gene mutations over the generations, the amount of which depends on the ability of heat shock proteins. When stress is applied such as change of survival environment, ability of heat shock protein cannot catch up, accumulated mutation appears as a phenotype at once. If this phenomenon responds well to environmental changes, wouldn’t it be an evolutional leap of living things?
The function of a neuron is to generate an electrical pulse signal for a stimulus, which is transmitted end to end in the cell. Neurons were thought to exist only in multicellular organisms, but similar functional molecules were found in unicellular Chlamydomonas. It is a channel rhodopsin. It is a protein that responds to light stimuli. In addition, Chlamydomonas has genes that do not form synapses but are necessary for synapse formation, receptors for neurotransmitters, cell adhesion molecules and lining proteins of the plasma membrane. Chlamydomonas is believed to have appeared in the living world 1 billion years ago. Chlamydomonas, which has flagella and has the function of generating nerve pulses, is reminiscent of hair cell sensors possessed by multicellular organisms. In the channel rhodopsin, a rhodopsin, in which opsin protein and a retinal are bound, also acts as an ion channel to form a light-gated ion channel. Since it is possible to control nerve activity with a laser in animals into which the channel rhodopsin is properly introduced, it has been applied as a brain function analysis technology (optogenetics technology).
The sudden appearance of Cambrian organisms on Earth is partly due to the loss of strata before 500 million years ago. For example, in the Grand Canyon, under the Cambrian sedimentary rocks that began about 540 million years ago, there are fossil-free crystalline basement rocks that formed about a billion years ago or more. Since this period was also important in the evolution of life, the disappearance of fossil evidence is a great loss.
Several lines of evidence suggest that the missing strata may have been glacial erosion during the Snowball Earth era. For example, a celestial body with a diameter of more than 10 kilometers is said to have collided with the Earth once every 100 million years. It is difficult to trace of such craters due to weathering, etc., and it is said that it can be traced back to at most 600 million years ago.
An examination of the moon's craters has determined that 8 to 17 craters with diameters of 20 kilometers or more were created at the same time, about 800 million years ago. In other words, it is thought that a group of meteorites hit the moon. It is known that meteorites with a mass about 20 times fall on the Earth larger than those that fall on the moon. It is possible that meteorites weighing 30 to 60 times as much as the meteor that wiped out the dinosaurs 65 million years ago hit the Earth.
It has been reported that about 800 million years ago, the concentration of phosphorus in the ocean increased fourfold, prompting the diversification of living organisms. In addition, a Neoproterozoic Oxygenation Event occurred 700 million years ago in which the concentration of oxygen in the atmosphere increased, suggesting the possibility of increased plant activity. The whole Earth was frozen twice during 800 to 600 million years ago. At the same time, the South Pacific superplume began to rise and the supercontinent Rodinia began to break apart.
Oxygen levels began to rise exponentially 600 million years ago, as the thick glaciers that covered the planet melted. Warm oceans were created between the split continents, and it is thought that full-scale evolution of organisms using oxygen began to create larger body. By about 550 million years ago, the next supercontinent, Gondwana, had formed and soon began to break apart. Fossil remains of the Ediacaran fauna as multicellular organisms from this period.
The first continents formed on Earth during the Paleozoic era. 2.8 to 3.8 billion years ago. The zircon that forms when magma hardens is hard and resistant to weathering. Radioactive decay records of uranium atoms in zircons and hafnium isotope ratios allow us to estimate the age of zircon formation. Investigating the formation age of zircons collected from the old continents, it is thought that the continent grew due to intense volcanic activity every 200 million years.
The 200-million-year cycle coincides with the interval at which the solar system passes through the four arms of the Milky Way galaxy. A hypothesis is proposed that it is related to volcanic activity. Because the arms of the galaxy are so dense with stars and interstellar matter, when the solar system passes through them, the Oort cloud is disturbed and many comets are produced. When the comet hit the Earth, it pierced the crust and caused violent volcanic activity.
The evolution of unicellular organisms to multicellular organisms seems to have taken place over and over again in the plant family alone. The multicellularization occurred repeatedly at least in brown algae, yellow-green algae, and so on. In other words, multicellular plants have evolved in multiple lines. On the other hand, in animals, multicellularization seems to occur only in a single strain. The immediate ancestors of multicellular animals are thought to be unicellular organisms called the Choanoflagellates. It evolved from the Choanoflagellates through the sponges to many multicellular animals.
In lower multicellular organisms, where the cells are clustered together, there is a high degree of cell independence. All parts of their body have the ability to regenerate the whole body. Today's plants have similar regeneration capabilities. Before the development of multicellular organisms with differentiated functions, the substance that wraps the cells in a group must have evolved as the basis for the cells to gather together. In modern life, it is an intercellular matrix, a complex polymer composed of proteins and polysaccharides in animals.
However, multicellularization is not always an aggregate of one type of cell. Given the history of symbiosis those days, it is highly possible that many kinds of unicellular organisms formed an aggregate. By creating aggregates, cells could increase the probability of survival in harsh environments. When there is no food, some of the cells that make up the aggregate are sacrificed to help the rest of the cells, maintaining the organism as a whole. The currently observed bacterial biofilms are a typical example. Biofilms are formed by multiple bacteria in a viscous matrix that is primarily composed of polysaccharides. They are usually formed on the surfaces of objects, especially they are also formed inside animals, in order to be resistant to environmental changes, disinfectants, or immune responses.
A hypothesis is that gene sharing would have had progressed among the various types of organisms that have formed aggregates, and changed from aggregates of cells with diverse genomes to aggregates of cells with one type of genome. In particular, some cells differentiated as germ cells and developed a reproductive system that exchanges genes.
In order for cells with a uniform genome to assemble, it is necessary to strictly distinguish cells having own genome from cells having other genomes. When it was a single cell, the cell membrane was a distinction between self and others. It is the receptor on the cell surface that distinguishes self from others (non-self). Receptors on cell membrane capable of identifying self on a large number of individual cells has been prepared and evolved. At the same time receptors that recognize other cells developed to recognize food and enemies.
An aggregate of cells that share the same genome eventually develops into a cluster of cells that share various functions. An example is a germ cell. A germ cell must be preserved forever to convey all functions as genes to the next generation. Then, all cells of the body with the necessary functions are differentiated from the germ cells. By making germ cells resistant to environmental changes, organisms have new survival strategies. That is, fertilized eggs, spores and seeds.
Estimating from the gene evolution clock, multicellularization began 900 million years ago. At first, marine sponges and other animals diverged. After that, the diploblastic animals such as jellyfish, sea anemone and hydra were branched from the marine sponges, and the triploblastic animals, a group of major animals now, branched from the diploblastic animals.
These organisms are not simply aggregates of cells, but are formed from differentiated (having a role) cells. Roughly speaking, the jellyfish and sea anemone are of a ball with a follow. It splits into outer cells (ectoderm) and inner cells that form the digestive system (endoderm) (two germ layers). In the three germ layers, there are cells between the outer and the inner cell layer, called mesoderm. When considering the human body as a cylinder, the outer side, that is, the skin is the ectoderm, the inside of the cylinder, that is, the gastrointestinal tract is the endoderm, while the muscle and the bone are mesoderm.
On the outside of multicellular organisms, a membrane of cells called the epithelium was created. It is necessary to have the ability of cells to strongly adhere to each other in order to protect the organism's body from impact. At the boundary with the outside world is called epidermis (skin). However, mucosal epithelium was formed on the surface followed inside the body (inner side of digestive tract etc.) due to material exchange.
The parts (organs) of the body of an organism are wrapped in a cell sheet called epithelium as well. In the stomach (abdominal cavity), it is called serosa and consists of mesothelial cell epithelium. By wrapping with the epithelium, it created a specialized space. Cells can be placed in epithelial bags, and various functions such as liver, kidney and reproductive organs can be formed as independent organs. Organs are connected with blood vessels and nerves. The environment of the body has become possible to keep in a certain condition, to store nutrients, for internal organs to have specialized functions, and to make their own exercise.
Collagen protein is used to physically strengthen membrane of epithelial cells. The amino acid composition of collagen is biased consisting of simple amino acids, 1/3 of glycine, 21% of proline and its derivative, 11% of alanine. It has a simple backbone consisting of repeating 3 amino acids with a glycine and two other amino acids.
It is thought that collagen was first born on the Earth after the snowball Earth age in the late Proterozoic period (600 - 800 million years ago). Unicellular organisms that produced collagen were used it for cell-to-cell adhesion, promoting multicellularization. Collagen is, so to speak, a clothing, a cradle, a structure to call a room. Collagen is the major protein that constitutes the connective tissue of animals, and in mammals it is the most abundant protein that makes up 25% of the total protein content. In other words, in the animal body cells are wrapped in a collagen cocoon.
Coelenterates, such as jellyfish and hydra, are now thought to be the lowest living organisms with nervous systems. The nerves of coelenterates are called the diffuse nervous system and have no central nucleus to control. Their nerve cells are connected by nerve fibers.
Even lower sponges seem to have prototypes of nerve cells. Sponges have no internal organs, and have waterways running through their bodies like a mesh. The sponge cells were isolated one by one, and the nucleotide sequences of the expressed mRNAs were examined to classify them into 18 types. Genes that constitute synapses were expressed in neuroid cells and digestive cells. However, they do not form synapses.
About 680 million years ago, the triploblastic animals were divided into groups of deuterostome animals and protostome animals. A group of protostome animals was divided into a group of Ecdysozoa including arthropods and round worms and a group of Lophotrochozoa including molluscs and Plathelminthes. From deuterostome animals, sea urchin and sea squirts appeared. These multicellular organisms are difficult to become fossils, so there is no geological evidence left.
Ediacaran Period 635-542 million years ago. Ediacaran organisms from 500 million years ago are the first to appear as fossils of visible size. The name comes from the Ediacaran Hills in Australia where the fossils were first discovered. The Ediacaran biota was found on the island of Newfoundland in Canada. The animals with only a soft body were preserved as a fossil because a volcanic ash buried the bodies in a short time by a volcanic eruption. It has also been found in Russia and India.
Most Ediacaran organisms are found between 570 and 541 million years ago. Dickinsonia was a thin, flattened organism over one meter in size. The most popular theory is that they are animals, but other theories are that they are giant single-celled protists, lichens, algae, and bacterial colonies. Fossils excavated from Russia were not thermally denatured and the organic matter was removed and analyzed. The round-shaped Beltanelliformis was inferred to be a cyanobacterial colony from lipid analysis. In Dickinsonia, an organic substance with 27 carbon atoms, which seems to be derived from cholesterol, was detected, so it is presumed to be an animal. The organic matter separated from the layer immediately above and below the fossil was 70% stigmasterol with 29 carbon atoms and 11% cholesterol, so it was an algae fossil.
The Ediacaran creatures do not appear to have lived an active life. There are those with left-right symmetry and those with three-fold symmetry. At that time, the shallow sea was covered with stromatolite, and the bottom of the sea was covered with a cyanobacteria mat (a biomat: a slimy texture made of microbial membranes covering rocks and ground). If it was a plant, it would have been seaweed, and if it was an animal, it would have lived on cyanobacteria mats. Most Ediacaran organisms are found on the ocean floor, and those that lived in burrows on the ocean floor are rare.
The Ediacaran biota declined at the beginning of the Cambrian period, 543 million years ago. There is a theory that the cause of the decline was related to the explosive volcanic activity at the beginning of the continental split, and that it was devoured by the Burgess fauna that appeared in the early Cambrian period. Around this time, creatures that live in holes on the sea floor can be found. In other words, it is interpreted as hiding from the enemy.
A large amount of fossils are discovered from the early Cambrian period (543 million to 490 million years ago). It seems that organisms have appeared suddenly, so call it Cambrian explosion. Fossils around this time contain Burgess animals, famous for strange large organisms such as Anomalocalis and Opabinia. They are named after the Burgess shale where fossils were stored. As the soft part of the body remained completely, we were able to investigate the structure and function of the animal's body in detail. Trilobites, well known fossils, also prospered in those days.
Many direct ancestors of the present living organisms also appeared in this period. Arthropods (spiders, scorpions, horseshoe crabs and trilobites), chordates (with the notochord of the backbone) and vertebrates. Chordates animals, which are prototypes of living organisms with backbone that became our ancestors, are only a few centimeters in length and belong to primitive fish, such as jawless fish.
From the evidence of fossils, the appearance of Burgess fauna is sudden. The rapid evolution is the result of accumulation of previous genetic mutations. Crustacean animals and arthropods are known to grow as small plankton during larval period. In the earlier Proterozoic era when fossils are not found, it is thought that living organisms overcame the cold season as a small plankton. There are various opinions on opportunities to achieve large size and opportunities to build armor, but I want to mention that the oxygen concentration in sea water has increased to a certain concentration and the global warming.
Predators can get nutrition and energy quickly by eating other creatures. It is predictable that the predators had advanced eyes and had high motile performance. They would have used aerobic respiration for their movement. Also, they developed a integrating nerve tissues to control their muscles based on the information of the sensor. The neural circuit as a system is thought to appear first as the scattered nervous system of hydra and jellyfish. It is necessary for big body to have a mechanism to efficiently carry oxygen and nutrients to whole body. On the other hand, many animals have developed mineral exoskeletons when the emergence of large predators. It is thought that the relationship of food chain was born in the period of Cambrian explosion. The relationship of the eat and eaten added arms race to evolution process.
The Pax-6 is the gene that gives the first command to make eyes, that is, the master control gene. The most primitive organism having the Pax-6 gene is planaria. The organism created an apparatus with dent on the surface of the body and placing photoreceptor cells on its bottom to know the direction of the light source. Planaria belongs to Order tricladdida in Class Turbellaria in the Platyhelminthes and is the branch point between Ecdysozoa and Lophotrochozoa. The flat body reminds us of the Ediacara biota. As a result of the evolution, the dent has a lens, and the photoreceptor cell forms a sheet called the retina, which projects the external world. The apparatus became an eye to recognize the world.
Trilobites are thought to have taken up mud with a lot of limbs and were feeding nutrients together with mud. There are a lot of characteristic drilling traces (living traces) left. Biomat played the role of canvas for the living traces. Samples of late Cambrian or early Ordovician period (about 500 million years ago) have walking traces of animals left on sediments close to the ocean. It was a large arthropod with at least 4 pairs of walking limbs, probably of a eurypterid, and the trace of the tail could be discerned. While digging under the biomat covering the surface of the ocean floor, some animals were eating humus of biomat, and tunnels are left as trace fossils.
A large amount of phosphate was accumulated in the Cambrian period, and it became phosphate ore. After that, speaking of phosphate ore was bio-origin. A typical example is guano, which is feces of birds.
The Gondwana continent passed Antarctica from Ordovician to Devonian period. Most of the lands at those periods were in the southern hemisphere. The protrusion then weathering of the mountains of the Appalachian range affected the chemical composition of the atmosphere and the ocean. Particularly, carbon dioxide was immobilized as rocks.
The Cambrian creatures mostly died out 500 million years ago and Ordovician creatures emerged. In a word, it was the emergence of the sea of fertility. The relationship of living things became complicated, and seascapes like the current coral reef were created. As the Cambrian creatures suddenly appeared as a fossil, it was named a large explosion of evolution with a meaning of surprise. The Ordovician creatures brought the diversification of living organisms far beyond the Cambrian period.
A representative organ of the organism born in the Ordovician period is a calcareous shell. Stromatoporoid, corals, Brachiopoda (lamp shells), snails, sea lily and nautilus (ancestors having shell of octopus and squid) appeared. The shells are thought to be as equipment to protect them. The creatures in the ocean thrived which can protect themselves from carnivores. In the Paleozoic era, Stromatoporoid that creates reefs was prosperous. After the Paleozoic era, fixation of carbon dioxide by living things was done on a large scale in the sea. Besides coral, there is plankton with shell made from calcium carbonate in the ocean. Creatures may have contributed to the reduction of carbon dioxide. The Ordovician period was relatively cold.
The evolution of chordates to vertebrates, that is, the birth of fish, occurred in the shallow sea of the late Cambrian. The first vertebrates to appear are jawless fish. Among the jawless fish, there appeared ones that protected the body by adhering calcium phosphate crystals to the body surface, which was advantageous for survival. It was the crustaceans in the Ordovician that completed the armor of calcium phosphate as a carapace. The ancestors of this species of vertebrates do not live today. The existing round-mouthed animals lose their carapace and become naked. During the process of evolution, it changed from the exoskeleton called the carapace to the endoskeleton.
Collagen fibers are proteins of the outer coat that were born when organisms became multicellular. Vertebrate bones are built in cartilage. The primordial vertebrate body surface would have been covered with thick collagen fibers. The first bone was calcium phosphate secreted into the collagen fiber of the skin and covered the body like an armor. Currently the skull bone is a human remnant. The carapace is a small piece like a tooth, covering the body like scales.
In the vertebrate animals that lost the exoskeleton, the endoskeleton developed. Bones that protect nerve tissue like spine. Bones that protect visceral tissues like ribs. And limb bones for exercise. The turtle shell is a rib. Teeth were arisen from the skull as ones of the exoskeleton. Vertebrate bodies are also divided into somites like insects, and vertebrae are the basic unit. You can see the effects of somites on the development of bones and internal organs in the fetus.
In the Ordovician period, vertebrate was divided into a jawless vertebrate, such as lampreys or hagfishes, and Gnathostomata which has a jaw. Later, in the vertebrate lineage, Gnathostomata appeared in the sea one after another from Devonian to Silurian period. Quadrupeds evolved from Gnathostomata about 400 million years ago in the Devonian period.
The genes RAG1 and RAG2 catalyze a genetic recombination of V (D) J genes of antigen receptors such as immunoglobulin, and realize diversity of acquired immunity. These genes are thought to encode a transposase derived from a mobile genetic element inserted into the vertebrate genome at 450 million years ago. Therefore, the establishment of acquired immunity is around Ordovician period.
The world of various creatures in the ocean produced in the Ordovician period has been partially extinct several times, but lasted about 250 million years until the Permian era. This period is called Paleozoic era. Every time on extinction of a comparatively large extinction occurs, "period" changes. The Gondwana supercontinent reached the Antarctica and became cold, so the glacial period and interglacial period began to occur alternately. There is extinction of living creatures, about 57% of the genus has been extinct. Then the Silurian period started. In the Silurian period, the plants advanced onto the land.
During the Caledonian orogenic movement, the Iapetus Ocean became a land in the Silurian period. In the Silurian period, plants expanded to the land, arthropods followed them. Furthermore, fossils of plants with the vascular bundles have been found at the end of the Silurian period.
When enough oxygen was accumulated in the atmosphere, an ozone layer was formed. The ozone layer acts as a barrier to cut off harmful ultraviolet rays, allowing organisms to move to the land. It is about 420 million years ago. Compared with in the sea, there were still a lot of ultraviolet rays lethal to life on land, and furthermore, a structure to support the body and mechanism for preventing drying are necessary because there is no water nor buoyancy. On the other hand, there was also a favorable condition that the oxygen concentration was much higher than in the sea, and there were no competing organisms. It was an attractive environment for plants in the sense that both light intensity and carbon dioxide amount are much higher than in the sea.
Lichens (mosses) appeared, followed by plenty of Pterophyta. The oldest land plant fossil is the spore and sporangia of a moss found in Oman. It is 470 million years ago (Ordovician period). The oldest fossil of the plant is Cooksonia and it was of the middle Silurian period (425 million years ago). Even though it was a Pterophytum, the leaves were yet not differentiated and it had only a stem. In order to withstand drying, plants must have stomas that allow moisture regulation. They also needs a structure bundling thin tubes (plant vascular bundle) that can carry water and nutrients against gravity. The plant vascular bundle evolved more and more efficient structure, at the same time, the stem became robust.
After plants succeeded on land, animals like mites eating rotten plants advanced to the land and then insects did. The oldest insect fossil is 400 million years ago (Silurian period) discovered in Scotland. Since animals need to support the body on the land without buoyancy and to withstand drying, the arthropods were able to land easier because their body was covered with external skeletons. In order to move around on land, the external skeleton was divided by the joints, and the motile organs such as the foot were prepared to support their body.
Here I briefly summarize history from the division of Rodinia Continent to the formation of Pangea supercontinent. During the collision of the continent, two large orogenic movements occurred, that is, the Caledonian and the Variscan orogenic movement, resulted two large mountain ranges were formed.
Around 600 million years ago, the Rodinia continent split into four continent, the Gondwana, the Siberia, the sub Laurasia (North America and Greenland), the Baltica (Northern European land masses including the Baltic Shield and the land masses of West Africa around Morocco). The Gondwana continent was in the Southern Hemisphere and the other continents were in the Northern Hemisphere. The relatively shallow ocean is called the Iapetus Ocean, which was surrounded by the Siberia, the Laurasia subcontinent, and the Baltica.
In the Ordovician period, the Iapetus Ocean was sandwiched with the Lauracia subcontinent at the West and the Baltica continent on the East. The Baltica continent approached the Lauracia subcontinent and the Iapetus Sea disappeared at the end of the Silurian. We call newly formed continent as the Euramerica continent. At the place where the Iapetus Ocean was, a large mountain range was formed from the Scandinavian mountains in Norway and Sweden, through UK and Ireland, to the Appalachian mountains range on the east coast of North America. This is called the Caledonian orogenic movement. The Caledonian orogenic movement occurred 420 to 390 million years ago (Devonian period).
The Rheic sea expanded during the Caledonian orogeny movement. The Gondwana continent located on the south side of the Euramerica Continent across the Rheic Sea, and the south side of the Gondwana continent reached the Antarctic in the Carboniferous period.
The Variscan orogenic movement occurred during the Carbonifeous period (3.5-2.9 million years ago). This orogenic movement is a subduction of the Rheic Sea under the Euramerica and Siberia continents. The collision between the Euramerica and the Gondwana continent of the west side made the Rheic Sea close in the late Carboniferous period. As a result, a large devastating mountain range from Czechoslovakia, Germany, Belgium, Northern France, to the Iberian Peninsula were formed. The eastern side of the Rheic Sea is renamed the Old Tethys Sea. The Old Tethys Sea was surrounded by the Euramerica continent and the Gondwana continent.
Finally, the Siberia continent collided with Euramerica Continent, the Lauracia continent was completed and the Ural mountain range was formed at the collision surface. The Lauracia continent and the Gondwana continent gradually approached, and the Pangaea supercontinent was made at the end of the Permian period.
Since the two major continents collided at that time, its scale of the influence was the largest in history. The formed mountain ranges was, from the west, the Appalachian Mountains of North America, across Europe, the Iberian Peninsula, the southernmost part of England, Belgium, Northern France, Central Germany, West of the Czech Republic. Furthermore, as the second stage, the old Tethys sea subducted under the Lauracia continent, for extension to the east, Tenshan, Altai, and Great Hingan mountain ranges of Central Asia were formed at the subduction zone. Further going to southward along to the subduction zone, from the mountain ranges of the eastern part of the Indochina Peninsula, it reached from eastern Australia to the Antarctica at the subduction zone of Panthalassa Ocean.
The Sinmeria subcontinent, which was on the north side of the Gondwana continent, moved northward and collided with the Laurasia continent as the Paleo-Tethys Sea disappeared. A mountain range extending from northern Iran to Afghanistan was formed. The sea between the Gondwana continent and the Sinmeria subcontinent expanded, opening the Tethys Sea. By this time, two land masses, Yangtze and China-Korea lumps including North China, collided with the Siberia continent.
Along the Caledonian orogeny stage, the Iapetus Sea became a land in the Silurian period. In the Silurian period, plants moved on the land, arthropods followed them. Furthermore, fossils of plants with vascular bundles have been found at the end of the Silurian period. During the Devonian period, forests were formed, and freshwater fish, insects, first amphibians (Ichthyostega) and others evolved to adapt to life on the land. The Rheic Sea closed in the late Carboniferous period by the Variscan orogenic movement. In the Carboniferous period, forests (scales) of large trees and conifers, which are gymnospermae, appeared in low humidity areas. In the Permian period, a variety of insects and other arthropods have emerged, including mammalian ancestors and primitive reptiles, which can enjoy a complete land life. Pushed by two orogenic movements, organisms accelerated adaptation and evolution to the land life.
The Devonian period is called "the age of fishes", and the original form of a vertebrate was created. Early bony fish, which appeared in the Silurian period, had an inner skeleton made of calcium phosphate, that is, a mineral reservoir. So, it was able to enter the brackish water and fresh water area. Bony fish flourished in the freshwater area of the Devonian period and were the ancestors of most of fishes today. As rivers and lakes are under various climates, fish evolved variously, under ecologically isolated environments. They then gradually returned to the sea in the latter part of the Devonian period.
It was the placoderms that dominated in the sea in the Devonian period. The placoderms are the first fish with a chin and had a hard armor. Fossils with placenta and umbilical cord were found in the placoderms. Early Gnathostomata seemed to have a wide ability of internal fertilization and viviparity. The origin of viviparity dates back to 360 million years ago. Modern sharks have the same mechanism. A primitive fish had a fin from the back through the tail to the belly. Fish got two pairs of fins, pectoral fin and pelvic fin from there. The gene that dominates the structure of the body is the Hox gene.
Lobe-finned fish (sarcopterygian) and ray-finned fish (actinopterygian) diverged 420 million years ago. Most modern fish are ray-finned. The radial bone is directly attached to the shoulder in ray-finned fish. Ray-finned fish is found to have 11 genes necessary for the construction of lungs and transcription factor genes that induce joints with synovial membranes, the genes necessary for life on land. For example, a pulmonary surfactant that smoothens the expansion and contraction of the lungs. and a transcription factor that induces the right heart dedicated to the pulmonary circulation. But ray-finned fish has no lungs, no joints, no right heart.
Only two species of lobe-finned fish survive. They are lungfish and coelacanth. The fins are fleshy, and the arm is attached to the shoulder, and the fin is at the end. Lungfish diverged from the branch of land animals 430 million years ago. Lungfish have a capillary-dense tissue, the lung, that branches off from the esophagus. There are also new pulmonary surfactant genes, five toe genes and nerves that reach the arm muscles.
It was supposed 380 million years ago that the lobe-finned fish such as Eusthenopteron began to live on the land. It may be that the flesh fins developed to move in the water with many obstacles while pushing obstacles, which is usually seen on the land. It seems that lung respiration develops in a shallow swamp or somewhere, where fish is difficult to breathe due to turbid and stagnant water. To feed insects on land above, the head became flat, the eyes moved upwards. The eyes peek above the water surface while the body is under the water surface. Get food by jumping with flesh fin.
The amphibian evolved from the sarcopterygians. The most primitive tetrapod is Acanthostega and Ichthyostega in the late Devonian period, and these had 8 fingers and 7 fingers, respectively, on each foot. The emergence of amphibians is the late Devonian. Although the inland area was dry, the large forest kept moderate humidity and created a cradle environment for amphibians. In land life after organisms arrived on land 440 million years ago, herbivorous vertebrates, vascular bundles, flight ability, echolocation, homeothermia, and color vision emerged. And these nine abilities were transferred from land creatures to aquatic creatures.
Again it became globally cooling, and 35% of the genus had been extinct. Probably, the reduction of carbon dioxide caused cooling, due to weathering and formation of soil by diversification of land plants. The relatively slow extinction means global warming was also the cause of the extinction after cooling. The genealogy of land plants is summarized in the chapter on Carboniferous period.
A huge coal field that exists now from North America to Europe originates from plants that flourished during the Carboniferous period. In West Virginia in the United States, a coal layer of 17 meters thick formed over 350,000 years are overlaid in 117 layers.
The ozone layer was completed in the Silurian period (about 450 million years ago), then plants were able to evolve on to the land. In the long Devonian period, the fern plants equipped stomata that regulate evaporation of water, fibrovascular bundles carrying water, and spores resistant to dryness. They formed large forests during the Carboniferous period. Fern plants could not leave from the waterside because their fertilization requires liquid water in their life cycle.
The oldest tree in the world, Cladoxylopsid, is a tree like a palm tree about 12 meters high in the Devonian period (393 million to 372 million years ago). As a result of analysis of the fossils, a large number of pillars of the wooden part forming the vascular bundle were lined up to form a hollow trunk.
Because not so many animals were landed which ate plants, the large forests fell down then stacked and deposited as they were. That is, the carbon in the plants was buried under the ground. As the settlement of accounts, the oxygen produced by photosynthesis was reminded in the air, the oxygen concentration in the atmosphere rose. At the time of plant landing, oxygen in the atmosphere was about 1%, but it reached 30% or more (now 21%) from Carboniferous to Permian period (350-250 million years ago). The Gondwana continent, which was in the southern hemisphere, was covered by glaciers 300 million years ago in the middle of the Carboniferous period. Cooling in this period is thought that the carbon dioxide concentration in the atmosphere decreased as a result of the burial of the terrestrial plants that flourished in the ground. Lignin-degrading fungi appeared at the end of the Carboniferous period, and ferns finally began to be decomposed completely.
Arthropods landed after the plants. From the stratum of the late Silurian (415 million years ago), fossils of scissors (spiders, ticks) were discovered and this is the evidence of the oldest crustacea on the land. Because arthropods were covered with shells, they are relatively resistant to dryness. Arthropods were able to live on the land if equipped with a mechanism to take in oxygen directly from the air (stigma. pore opening in the body surface of the stigma is called as spiracle).
Fossil footprints of huge arthropods, eurypterid (330 million years ago), were found in the northern part of England. From the size of the footprints, it was presumed that the body length is 1.6 meters and the width is 1 meter. In addition to the traces marked with three pairs of feet, the traces of dragging the tail remained clearly in the middle, not in a state floating in the water. But it is thought to be a trace that went out of the water and was walking. Eurypterid is an arthropod that is close to contemporary crabs or scorpions that were extinct before 250 million years ago.
The ferns and the arthropods were making soil on the land that had been the desert until then. Soil is a mixture of weathered products of rocks covering the earth's surface and degradation residues of plants, composed by coarse inorganic matter, colloidal inorganic matter, organic matter, microorganism, soil water, and soil air. It is essential for stable ecosystem on the land.
Arthropods cannot grow huge on the land. Because the weight of the exoskeleton that supports the body is too large to maintain, the larger muscles are required to the heavier exoskeleton. This made the volume of exoskeleton be limited. Depending on muscle performance, the upper limit of the size is determined. Also, since the stigma is a device that passively takes in oxygen, aerobic respiration cannot be sufficient for them.
As the oxygen concentration rose from the Carboniferous period to the Permian period, the breathing problem of arthropod was solved. Insects had been able to evolve to huge size. Since the Permian period, the enormous coal field could not be formed, because the large insects began to eat plants. After that, insects became natural predators of plants, and for 300 million years, the deep symbiosis was developed between them. That is evolved and developed, the battle between insects and plants, and also dependence between them.
It is thought that adaptive emissions of insects occurred during the Carboniferous period. The reason is that insects invented the wings and advanced into the three-dimensional world in the air. Insects that have wings and fly in the sky appeared 300 million years ago (the Carboniferous period). About 250 million years ago (the Permian period), the ancestors of current insects almost appeared.
The common ancestor of angiosperms and gymnosperms is thought to have lived 310-350 million years ago (the Carboniferous period). The set of genes for producing spores in fern plants and for producing seeds in cycads are nearly identical. In other words, evolution from spores to seeds was nothing new at the genetic level, but simply a change in how genes were used.
It was extremely warm from 270 to 250 million years ago and the average temperature was 10 C higher than the current temperature. The forests of fern plants flourished and huge insects were flying around. In the early years of Permian period, the Pangea supercontinent was established. The Siberia continent finally collided with Pangea super-continent, and almost all the land was put together as one super-continent. The Pangea super-continent was like a crescent (C shape) divided at the center with the equator. The big ocean surrounded the continent is called Panzalassa. On the east side of the continent (inside the crescent shape), there was an ocean called the old Tethys Sea, with small continents and islands dotted around.
Fossil footprints left by terrestrial vertebrates which had four limbs were dated about 400 million years ago. It was found in the Zachelmie rock quarry in the Holy Cross Mountains in Poland. Some of the footprints are extremely good in preservation state and allow detailed examination of the form of the foot part, which is similar to Ichthyostega, a primitive tetrapod in the early stage. It is 18 million years older than the oldest fossils of tetrapod body.
The emergence of amphibians was the late Devonian period. Although the center part of continents was dried, large forests created a cradle environment that maintained moderate humidity. From Amphibian, amniotes were branched, which produce eggs with shell, and expanded their habitat to more dry land. The catalogue of creatures at the time when they started to advance to the land are not organized, many species were extinct. From the amniotes in the Permian period, the diapsids (ancestors of dinosaurs and reptiles) and snapsides (mammalian-like reptiles, ancestors of mammalian) evolved. Mammalian-like reptiles, such as Dimetrodon, established their hegemony on the land, and their size was reached to about 3.5 meters.
In the Permian period, there were various plants, huge amphibians and reptiles inhabited in the world. Among them, abundant fossils were found of mollusks, echinoderms, and brachiopod from the shallow sea sediments of the Permian period. Trilobites and others were prosperous. In plants, gymnospermae such as Ginkgophyta and Cycads also began to prosper in addition to fern plants. A large number of insect fossils were discovered in the northwestern part of China during the PT mass extinction (233 million years ago). They are up to 28 families, including insects with incomplete metamorphosis and some with complete metamorphosis.
At the end of the Permian period (250 million years ago), the greatest extinction occurred in the history of the Earth. At that time, 96% of marine invertebrate species have disappeared. The extinction of the Guadalupian Age occurred 7 million years ago from the PT extinction. The cause is Emeishan Traps in southwestern China. Mt. Emeishan is a mountain in Sichuan, China, around which basalt lava has spread. It was mainly active from 262 to 261 million years ago and produced a large amount of lava of about 1 million cubic kilometers. The Great Extinction at the end of the Permian period was a huge eruption called the Siberian Trap.
The oceanic plates that subducted to the surroundings of the Pangea super-continent began to fall toward the nucleus of the Earth at the same time, and as a back-action, a huge super hotplume occurred toward the surface of the earth. A huge volcanic activity occurred in the ancient China, a large eruption lasted about 600,000 years. This activity is said to make the Siberian flood basalt. The Earth was covered with a large amount of volcanic ash, and the plant died due to cooling and darkening. After that, the atmospheric carbon dioxide has doubled with the gas from the volcano activities, and the average temperature had risen by 5 C due to the greenhouse effect. The rise in temperature caused the methane hydrate to collapse, then the released methane further accelerated the greenhouse effect. It is thought that oxygen deficiency was long lasting because methane burned and plants were decreased. Clams with an advanced respiratory system seemed to be able to survive in this change. Unicellular Fusulina species and trilobites proliferating for a long time had been extinct. Small number of Corals, Sea lilies, Brachiopoda, Bryozoa and Amonites were left in the following Triassic period.
Not only in the ocean but also on the land, living organisms have been extinct in large quantities. Mammalian-like reptiles also experienced several extinction phenomena over the long term in the late Permian period. Survivors on the land were organisms with an efficient respiratory apparatus. In the case of mammalian-like reptile, they separated nose and mouth, and were breathing using the diaphragm. In the other case, survived animals developed a circulatory respirator with air-sacs in addition to the lungs, like birds (also dinosaurs). Plants are not usually extinct so much because descendants can be left as seeds resistant to dryness, although by the end of the Permian period, the plants were also largely extinct.
The Mesozoic era started from the Paleozoic era with the end of the Permian mass extinction. At the beginning of the Triassic period, the ecological space on the Earth was largely empty and not much organism. In the Triassic period, reptiles evolved greatly, and eventually the dinosaurs flourished on the Earth.
The evolutionary mechanism at the gene level is considered to be based on gene duplication. Examining the genes, many genes with similar nucleotide sequences or amino acid sequences are found and each has a different function. It is reasonable to think that gene duplication occurs, then their function has differentiated. Gene duplication may occur partially, sometimes doubling the entire genome. Two stages are hypothesized that genome had doubled.
One is the time when a eukaryote was born, about 1.5 billion years ago. In prokaryotic E. coli, the genome size is about 4,377 genes, the eukaryotic yeast genome size is 5,538 genes, and the malaria parasite is 5,268 genes. Although not doubled, new genes were added dramatically.
The increase in genome size allowed living organisms to afford to diversify the genes and became the basis for the Cambrian great explosion 600 million years ago. Multicellular organisms have double the number of genes compared to single cell organisms. The slime mold, which is usually a unicellular organism like ameba, but at the time of reproduction it becomes multicellular organism, has 12,500 genes. C. elegan, which is a multicellular organism, has 19,893 gene and sea urchin, which is a protochordata (ancestor of vertebrate), has 15,852 genes.
The second doubling in genome had occurred in the Ordovician and the Silurian period, because the organisms appeared whose genome size was further doubled. The vertebrate pufferfish has 27,918 genes and the human being has 22,287 genes. Fish, amphibians, reptiles, birds and mammals are thought to have about the same number of genes. For comparison, a rice plant has 37,544 genes.
In plants, tetraploid, hexaploid, etc. can be made by drug treatment. The polyploid increases the number of chromosomes, but not the number of genomic genes. Wheat was selected hexaploid by artificial choice, to increase the yield. When genome is multiplied, the size of the body tends to become large. The giantization found in Synapsida or dinosaur might be related to multiplication of genome size. In fish and amphibians, polyploidization is often observed, but not seen in reptiles, birds and mammals. Related to this or not, sex determination is strictly regulated by the number of genes in birds, reptiles, and mammals.
It is not only the case the entire genome duplicated. Multiple genes with similar sequences are found in the genome. It is called gene family. The largest gene family in the human genome is the GPCR superfamily, which has over 1000 members. Also, the Immunoglobulin superfamily contains 765 genes. These genes are considered to be duplicated and diversified from one ancestral gene. The gene duplication mechanism is thought to be a mistake (transfer) at the time of replication, gene recombination, or gene transfer utilizing replication function such as endogenous retrovirus.
There are cases where functional units are duplicated in genes. In other words, many genes have the same functional unit (a gene fragment). In particular, you can find a gene that joins two functional units. Partial duplication in genes in many cases occurs in exon as unit. It is believed to be caused by gene transfer utilizing replication function such as endogenous retrovirus.
Under the state where the function is hidden, that is, even if the gene changes but not affect the phenotype, so it is expected that various trials and errors can be made. Motoo Kimura, who advocated a theory that the most of the evolution at molecular level would be neutral, explained that the mechanism is essential to hide the non-neutral mutations for evolution at the phenotype level. Gene duplication and sexual reproduction are thought to hide such mutations.
Meanwhile, it is also necessary to have a mechanism for putting out the accumulated mutation at once. Such an opportunity is considered as a major change of the Earth, or the environment. Molecular mechanisms are under study in which gene mutations are manifest. Heat shock protein, which is one of the candidates, is produced when the cell is subjected to stress, correct three-dimensional structure of the denatured proteins by stress. It is pointed out that the mutation in the heat shock protein may cause many new mutated genes to function, which were originally dormant.
Mesozoic era (250~66 million years ago, Triassic, Jurassic, Cretaceous) came after mass extinction at the end of the Permian period 250 million years ago. The Gondwana continent was a huge continent composed with Antarctica, Australia, Africa, South America, and India, located in the high latitude region of the Southern Hemisphere and was the largest 300 million years ago. In the Triassic period, Pangea supercontinent existed. The old Tethys sea sank under the Eurasian continent at the subduction zone from the present Turkey, via Central Asia, to South China, and was about to disappear. The Tethys Sea had expanded at the south of the region through the present Tibet, Turkey and Iran plateau.
Large-scale computer simulation of mantle convection in the three-dimensional global sphere taking into consideration the physical parameters of the mantle was carried out on the process of the division of super continent Pangea 200 million years ago. The state of continental movement from 200 million years ago to the present was examined. On the actual Earth time scale, the great events on the Earth surface after the Pangea division, such as the expansion of the Atlantic sea and the collision Indian subcontinent with the Eurasian Continent, which moved at high speed to the northward, was reproduced.
In particular, anomaly high temperature of the mantle due to the heat shielding effect beneath the Pangea supercontinent might largely contribute to the division of Pangea supercontinent. The heat accumulated under Pangea was interpreted to have expelled from the mantle to the surface through the rifts. The main driving force that the Indian subcontinent moved northward at high speed was presumed to be a cold plume developed in the northern part of Tethys sea immediately after Pangea division. From the three-dimensional structure of the current mantle constructed by seismic tomography, the low-temperature region is confirmed deeply in the mantle ahead of the cold plume. India subcontinent without a subduction zone still continues northward, indicating that the driving force of continental migration is also a cold plume.
In the early Triassic period, the oxygen concentration fell to the lowest level ever since the Proterozoic era, at 10-15%. Living organisms adapted to that age were characterized by their body plan. The cardiac morphology is more advantageous in the 4-chamber heart (birds, mammals), where the arterial blood and venous blood are completely separated, than in the 3-chamber heart (amphibian, reptile). A good example is a dinosaur. Dinosaurs had a heart with 4 chambers and air sac. In reptiles, owing to the legs protruded sideways then advanced while twisting the body, the lungs are pressed and their breathing is less efficient. In contract, dinosaurs have the foot downright from the body. Also, the diaphragm was developed. The bird's air sac system has a one-way flow of air from the lungs to the air sac and is good breathing efficiency. Reptiles, together with ammonite, are creatures representing the Mesozoic era. In the Triassic period, reptiles expanded their living area to the land and the sea.
In the evolutionary tree constructed from gene sequence analysis, the reptile and bird groups diverged from the mammals 310 million years ago. At 270 million years ago, group of the tuatara, the common lizard and snake split from the branch. The normal lizard and snake groups split further at 250 million years ago. By the way, from the other branch, turtles (255 million years ago) and then crocodiles (245 million years ago) diverged, and then birds diverged via dinosaurs.
Dinosaurs evolved in various ways during the Triassic period (250-200 million years ago). The symbolic stratum is in the Carnian period (237-227 million years ago). The characteristic dinosaurs have evolved during this short 10 million years. The ancestors of Stegosaurus and Triceratops, Brachiosaurus, and Tyrannosaurus have emerged. During this period, it was rainy and warm, and the interior of the giant continent was dry and hot. There are no flowers, no grass, no bird. Mammals have found as fossil teeth. Coral ancestors were born in the sea. It is believed that the Langeria eruption at 232 million years ago would have caused the warming for millions of years. A huge basalt belt remains with a thickness of several kilometers that extends from British Columbia to Alaska in Canada.
Among the gymnosperms, the ginkgo species that appeared in the Permian period gradually extended their living area. In the Triassic period, the ginkgo species, pine woods, and cycads mainly formed the forests, where genuine ferns flourished under the tree. Early gymnosperms, ginkgo and cycads had naked ovules directly exposed to the outside air. In pine trees, ovules were covered with scaly organs made by deforming branches and leaves, forming cones and thus were protected. For fertilization, sperm cells directly extended a pollen tube to egg cells. This mechanism enabled the pine trees expand to almost the whole area on the Earth. Flowers with the first petals are estimated to have appeared 250-140 million years ago (Triassic).
At the end of the Triassic period, magma activity became vigorous in central Atlantic area, raising the concentration of carbon dioxide in the atmosphere. As a result, the temperature rose globally and 47% of the creatures of the genus died out.
The Triassic period (250-200 million years ago) ended and the Jurassic period (200-140 million years ago) began. Giant amphibians or the Therapsida were extinct that connects the dinosaur and the amphibian. Instead, in Jurassic period, a group of reptiles called dinosaurs came up to the top of the ecosystem. Taxonomically we call Saurischia and Ornithischia as dinosaurs. Dinosaurs are one of archosaurs, along with Pterosaurs and crocodiles. Pterosaurs that can fly in the sky and Plesiosaurs or Ichthyosaurs that lived in the ocean are not included in the dinosaurs. Dinosaurs were so prosperous to differentiate into various species.
Dinosaurs were able to walk with legs stretched right beneath the body, moving back and forth. Therefore, small dinosaurs have high exercise capacity and feed on other small animals. In addition, the legs extending right under the body were able to support a huge body. Large body was a major weapon on land where was easy to dry and the temperature changed drastically. Flying pterosaurs and birds were born in Jurassic period. It seems that warm-blooded animals also appeared among the dinosaurs. It is highly likely that giant theropods (herbivores) and ornithischians are heterothermic animals, and that small carnivorous theropods are warm-blooded animals.
Mammalian ancestry is Synapsid. Synapsids flourished in the Permian period, divided into reptile-like Saurischia and mammal-like Therapsida. The Saurischia were extinct by the late Permian period (2.5 million years ago). Therapsida survived in the early Triassic period, but died out in the late period. It is thought that mammalian ancestry evolved from Therapsida in the late Triassic. At that time, it is thought that they were still bearing eggs, but that they raised their child with milk. Examination of the inner ear in the fossils of synapsids suggests that the structure of the inner ear changed significantly during the Late Triassic period (237-210 million years ago) and body temperature increased by 5-9 C. The volcanic activity and cooling caused by the breakup of the Pangea continent probably promoted the evolution to warm-blooded animals. In addition, many mammalian fossils have been found in China from the Jurassic and Triassic periods, and has shown that they were as diverse as modern mammals. After the end of the Permian mass extinction, mammals also adapted to the empty ecosystem where the dominant species, amphibians, became extinct.
In addition, the newly emerging gymnospers formed a large forest. The ferns could grow only in places with high humidity, so the dry inland of Pangea continent was a wilderness. In the Jurassic period, gymnosperm plant made big forest and attracted lives.
Coral reefs were spreading in Tethys Sea. The northern coast of the Tethys Sea goes from the current Southeast Asia to the Middle East (India is still far south), reaching Europe and North America. South runs through the north side of India from northern Australia to the Arabian Peninsula, North Africa. Tethys sea was contact to the Atlantic Ocean, which was being opened, and the west of Tethys sea extends to South America.
A new movement of crust started and continued from the end of the Jurassic period to the Cenozoic era. One was the opening of the Atlantic Ocean. The rift extended to Gondwana continent, so South America and Africa were separated. Antarctica, Australia and India were separated from Africa and moved northward, except for Antarctica. Along with this movement, Tethys sea began to subduct under the Eurasian Continent.
The division of the continent created a global equatorial current. This ocean current ran round of the Earth at equator and was always warmed, so it did not cool down. The Tethys Sea is thought to be very warm because it was on the course of the global equatorial current. The Tethys Sea is thought to be full of food because many fossils of coral are found there in100 to 70 million years ago. There was no ice sheet in the Arctic or Antarctic.
In the Mesozoic era, oil in the Middle East was made indispensable for modern society. The Arabian plate, which accumulated oil later era, was located on the north side of the Gondwana supercontinent from the Precambrian period through the Mesozoic era, facing the big but unstable sea. Since the Gondwana continent was in the south, the Arabian plate was stably maintained within the equatorial region, not to collide with other continents, nor sink into the mantle.
The Arabian plate sank in the Tethys Sea in the Mesozoic era, and it seems to have accumulated a large amount of organic matter there. The temperate Tethys sea gradually closes, not only the Arabian plate, but also the North African and American oilfields were produced. The Arabian plate is currently colliding with the Eurasian Continent, raising the Zacros mountains of Iran. The Arabian plate is going to collide into the huge Eurasian Continent so the current Middle East oil fields will also be destroyed.
Marble, which is abundant on the European side of the Mediterranean Sea, is also derived from coral reefs created at this time. The Greater Adria continent separated from Gondwana 240 million years ago and moved north, developing coral reefs in the Tethys Sea. The Greenland-sized Adriatic continent subducted under the European continent along with the Tethys Sea 120 to 100 million years ago. appearing. According to CT images of the earth's interior using seismic waves, remnants of the submerged continent can be seen 1,500 km below the continent of Europe.
The Cretaceous period was characterized by high volcanic activity, a high concentration of carbon dioxide, and a warm climate. The ocean floor in the deep sea became hypoxic (ocean anoxic event). Accumulated organic matter was deposited as black shale, which became the source of petroleum. About 100 million years ago, the Great Transgression occurred during the Cretaceous period. The cause is thought to be the huge Mid-Atlantic Ridge formed by the splitting of the Pangea supercontinent. Two giant plateaus in the Pacific, the Shatsky Plateau (150-130 million years ago) and the Ontong Java Plateau (125-120 million years ago), also formed recently. Both consist of flood basalt from massive volcanic activity. Greenhouse gases such as carbon dioxide released into the atmosphere have accelerated global warming, causing rapid evaporation at the surface of the sea, and salty seawater has accumulated in the deep ocean, halting ocean circulation. This caused the oceanic anoxic event. Cretaceous oxygen-poor seas are consistent with oil-rich seabeds. Arabian Peninsula, central Siberia, around the Caspian Sea, Brazil and the ripping sea bed of the Gulf of Guinea, Mexico, east of the Rocky Mountains. Both were submerged under the influence of transgression.
From the analysis of genomes, it is estimated that the ancestors of marsupials and placental mammals diverged 180 million years ago. Fossils of the oldest marsupials were found in China earlier in the Cretaceous period 125 million years ago. This Marsupial is estimated to be as large as rats 15 cm in length and weighing 30 grams, climbing trees, eating insects etc. Because Marsupial remains in South America and Australia far from China, Marsupials are expected to live on the entire continent. Likewise, a fossil with size of dogs or cats of about 130 million years ago was found in China. The bones of the dinosaur child were found from its belly, and the image that the mammals lived overwhelmed by the dinosaurs should be corrected.
The Australian continent and Antarctica became to have independent ecosystems separated from Africa, South America and the Indian subcontinent by 150 million years ago. Noteworthy animals are marsupials. Especially platypus has properties of both mammals and reptiles. Mammals with a uterus appeared on other continents, and eradicated marsupials. Evolutionary phylogeny of mammals depends greatly on continental migration.
Dinosaurs in Cretaceous period became warm-blooded animals, and those appeared that sit on eggs and that feed baby animals. If it evolved as it is, those used free paws appeared, finally species like mankind appeared? However, the dinosaur existed on Earth for about 150 million years, but no one with civilization appeared.
Fossils of dinosaurs that had feathers on the body surface have been found one after another. For a long time, a question mark is attached to an Archeoptery that was originally recognized as a bird fossil, and the feather dinosaurs found in China and primitive birds "Confucius bird" are thought to be the origin of birds. In this case, the appearance of birds is early Cretaceous (about 130 million years ago). The dinosaur survived the mass extinction by the meteorite, which told the end of Mesozoic era, turned out to be a bird.
Angiosperms have changed for gymnosperms. Changes in the plant world also influenced the types of dinosaurs and changed from Jurassic types to Cretaceous ones. Sauropods, Apatsaurs (Brachiosaurs etc.) and Stegosaurs which were more and more gigantic became extinct, Iguanodon and horned dinosaurs (Triceratops etc), which had a more mobility and lived as a group, replaced them.
Angiosperm appeared first in the Cretaceous days when the dinosaurs were standing, then prospered greatly afterwards. It is thought that the species differentiation of insects occurred at the same time is due to co-evolution of angiosperms and insects. Colorful flowers with honey produced by Angiosperms attracted insects, and symbiotic relationships were established between them. Among insects which are prosperous now, bees, flies, butterfly and beetles diversified since early in the Mesozoic era. In the Cretaceous period, there were no herbaceous plants, so outside the forest was a wasteland.
At the end of Cretaceous period, 65 million years ago, the living world experienced the second largest extinction in its history. The cause is said to be a collision of a meteorite. A comet or small celestial body about 10 km in diameter had fallen in Chicxulub region of the Yucatan Peninsula, Mexico. It is estimated that the meteorite collides at 20 km/h, the temperature reached about 10,000 degrees at the collision surface and the pressure reached 600 giga pascals. Since 10 km is more than twice the depth of the ocean, not only the seawater but also part of the plate beneath the sea bottom would evaporate in an instant. Many creatures were sacrificed by the tsunami caused by the direct effect of the collision. Meanwhile, as an indirect effect, a lot of dust and gas soared to the stratosphere to block the sunlight then to make the Earth cool. The plant was temporarily hit hard. The animals at the upper level of the food chain were received the greater blows. It became a big trigger for extinction of the dinosaurs.
Several birds are believed to have survived the devastating event which extinguished dinosaurs 65 million years ago, and since then, they has rapidly evolved into a wide variety of species of around 10,000. Sexual urges that copulate with or attract affection of opposite sex drove a rapid evolution of 15 kinds of pigment genes related to feathers and its decoration in birds. The ability of birds to chirp and imitate sounds appears based on the same neuronal circuit as seen in humans. However, the evolutionary path that humans have reached this ability is different from birds.
The catastrophe that destroyed the dinosaurs wiped out 75% of all species on the Earth. Mammals larger than rats died out. A lot of fossils were found from Corral Bluffs, Colorado, USA, date back to 1 million years after the meteorite fell. Mammals the size of raccoons (6 kg) lived before the meteorite hit, but were extinct 1,000 years after the hit. The only survivors were 2-3 species of mammals weighing about 600g, roaming among the ferns. After 100,000 years, the number of species has doubled, and the body weight has become the size of a raccoon. The vegetation also changed from ferns to pine forests. 200,000 years later, walnuts and acorns have given way to forests, and mammal species have tripled in size, reaching 25 kg. 700,000 years later leguminous plants appeared and supplied proteins to mammals. Mammals have grown even larger, some species reaching 50 kg, and more diverse. Immediately after the meteorite fell, the average temperature rose by 5°C due to global warming. It is thought that large amounts of carbon dioxide were supplied by large-scale volcanic activity in the Deccan Plateau in India around this time. Warming was observed three times in one million years, each time changing plant communities and prompting changes in mammals.
Mammals forced out dinosaurs lacking adaptability to the environment, and placed at the top of the food chain instead during a short period of time. After the extinction of the dinosaurs, mammals established the status of predators on the Earth. In the history of evolution, as it has been several times in the past, mammals, a new predator, have become very diverse and have advanced into an ecological niche with changing forms and lifestyles.
Several species of birds are thought to have survived the catastrophic event that wiped out the dinosaurs 65 million years ago, and have since evolved rapidly into the nearly 10,000 diverse species we see today. Sexual urges for mating and attraction prompted the rapid evolution of 15 pigment genes associated with feathers and plumage. It turns out that the ability of birds to sing and mimic sounds is based on the same brain circuits found in humans. But the evolutionary path by which humans arrived at this ability is different from that of birds.
Researchers in 20 countries spent four years and deciphered the genomes (total genetic information) of 48 species of birds such as owls, hummingbirds, penguins, woodpeckers and so on. In addition, among the reptiles, they compared the genomes and genes of three crocodiles with birds, which have the closest relationship to reptiles. They discovered that there is a big difference in the rate of evolution. While birds were much faster to acquire new genetic traits, there was hardly any change in crocodiles that branched off from common ancestry with birds and with dinosaurs about 240 million years ago. It is about 116 million years ago that teeth have disappeared from birds.
The oldest beaked bird is the 90-million-year-old Ichthyornis fossil. A fossil head with a toothed beak was reconstructed using computer tomography. It is believed that the wings appeared around the same time. Birds appeared in ancient times, not after the dinosaurs died out.
As the super continent Pangea divided into the several continents, shallow sea was open along the edges of continents as the Atlantic basin opened. Phytoplankton grew massively and released a large amount of oxygen into the atmosphere. The plankton carcasses settled and the mass of organic matter increased in marine sediments dramatically. Because the organic matter was not decomposed at that time, the oxygen concentration in the atmosphere almost doubled. The metabolism of birds and mammals requires considerably more oxygen than reptiles. In order to grow a baby in the body (with the placenta), the oxygen concentration in the atmosphere needs to be high. The diversification of placental mammals coincided with the era of high oxygen concentration in the atmosphere.
Due to the outcome of the genome project, it is known that more than a third of mammalian genomes are retrotransposons and the related nucleotide sequences. Retrotransposons are "jumping" genes from one place in the genome to another. Among these, the Peg10 gene, which is essential for the formation of mammalian placenta, was discovered. By evolutional genetic clocks, it seems that placenta species were born with the jump of Peg10 gene 170-140 million years ago.
Mammals did not morphologically evolve so much during the long Mesozoic era, but should have developed significantly in terms of function. They had evolved various abilities necessary for survival in a new environment in the niche of the dinosaur ruled ecosystem. For example, ability of hearing and smelling to live in a dark environment such as night or inside of cave and information processing ability to detect foods or danger. A reliable breeding method of raising a child with milk. Originally milk was sweat; mammary gland was evolved from sweat gland. They also developed omnivorous ability of eating various things by diverse teeth, maintenance of body temperature and possibly habits like hibernation.
It seems that the basic system necessary for emotions had evolved 100 million years ago when various information was put together. They are the amygdala that controls fear and the neuro-hormones that control feelings, such as dopamine, oxytocin, vasopressin, endorphin, etc.
It is said that Placental mammals (Eutherian) appeared on the Old World on the Earth (North America?). The more capable Eutherian evolved while forcing Marsupials out and expanded their living area. Since South America and Australia were isolated before Eutherians invaded, marsupials were to be preserved. It was several million years ago that the Americas of the South and the North were connected (the Panama Strait was made).
The evolution of mammals in the Cenozoic era can be seen as a change in the number of species. Many ancestral shapes of mammals appeared during 30 million years. After that, the Earth suddenly began to cool down, and many groups were extinct. Ancestors of existing mammals came in 20 million years ago. The categories of living things are species, genus, family, order, class, and phylum. The basic unit at the time of extinction is the family. Mammals are the animal representative of this era, in addition, birds and teleost in oceans also largely evolved in the Cenozoic era.
The Cenozoic is divided into Paleocene, Oligocene, Eocene, Miocene, Pliocene, and Pleistocene. Among them, the biodiversity has dramatically increased in Pliocene and Pleistocene. This is because the frequency of appearance increased as well as the frequency of extinction. This is called the species turnover speed. In primates the turnover speed increased to Pleistocene, somewhat later than the other species. Turnover would be the driving force of great evolution eventually.
Looking at the balance between extinction and appearance based on the family, 35 families appeared per 10 million years, during first 40 million years in 65 million years. The number of extinctions has increased little by little, almost the same as the number of appearances in the Oligocene (34-24 million years ago). After that, the number of occurrences decreased, and it became 20 families per 10 million years. The extinction number rapidly increases after entering Pleistocene, it becomes 80 families calculated as per 10 million years. It is the influence of homo sapiens.
Whatever a mammal or a bird, their characteristic is the development of the brain. The species in which a pair of male and female makes a unit to live tend to have a significantly larger brain compared to the size of the body than other similar species. In the case of birds, the brain is even bigger of a species whose mating pair lasts for a long time. It is suggested that crows may possess intelligence equivalent to that of primates because they have the ability to make suitable tools without failure.
In dinosaurs, all teeth were almost the same shape, whereas mammals differentiated function in front teeth and back teeth. They can chew and grind food better. Among mammals, the best adaptation to eat plants is Artiodactyla, such as cattle and deer. This group can keep a plenty of plants in the stomach, soften them, then returns to the mouth and grinds and drinks again. This action is called rumination. By ruminating, they can eat and digest hard plants.
In the Cretaceous period, angiosperms, which have flowers, were diversified rapidly instead of ferns and gymnosperms. Angiosperms are flowering plants that are now normally found around us. The first reliable evidence of angiosperms is pollen fossils of about 130 million years ago at the beginning of the Cretaceous. A major group appeared in late Cretaceous. Angiosperms provide pollen and honey to insects which come to carry plant pollen. The interaction between both organisms is enriched and both have diversified. The basis is a bee. The ancestor of the bee has dates back to 100 million years ago (Cretaceous). Insects such as bees are also stored in amber as fossil.
Angiosperms are thought to have originated from gymnosperms, but it is not known yet which gymnosperm was an ancestor. The aquatic plants, Hidachiaceae and Sirens, are the first angiosperms that appeared in the Mesozoic era. In Hidachiaceae, the maternal tissue supplies nutrients to seed common to gymnosperms (conifers), not embryonic tissue like angiosperm plants.
Currently, angiosperms have about 400 families, 250 thousand to 300 thousand species. In the Cenozoic era Tertiary period, a genus that is flourishing to the present has appeared. Like mammals, the current species came out about 10 million years ago, and the species that characterize the Tertiary period disappeared by about 2 million years ago.
Gymnosperms and angiosperms have hard bodies derived from vascular bundles. Jurassic dinosaurs could not grind hard plants. Huge thunder dragon had a stone in their stomach. It is like a gizzard of birds. Teeth played only a role of tearing off the leaves. Cretaceous herbivorous dinosaurs are thought to be able to grind plants by developing cheeks and creating grinding teeth.
Angiosperm offers mammals and birds with fruits loading seeds which have shells not to be digested, and has taken a strategy to expand the breeding area. Plants are always in a position to be eaten on the food chain, so this strategy is on the evolution of symbiosis just like insects.
A rapid warming occurred 55 million years ago. It is called the Paleocene-Eocene Thermal Maximum (PETM). The methane hydrate collapse theory is the leading cause, but major changes in volcanoes and ocean currents are also conceivable. Over the course of 10,000 years, large amounts of carbon dioxide or methane were released into the atmosphere. The greenhouse effect increased the temperature by 5-8 degrees. This is the fastest warming in hundreds of millions of years. The climate was subtropical up to the mid-latitudes, and the polar regions had a subarctic climate with no frigid climate. Warming continued for about 10 million years. During this period, the change of vegetation from gymnosperms to angiosperms progressed rapidly. At the same time, artiodactyls, perissodactyla, and primates appeared and diversified. In theory, it would have been a mass extinction, but surprisingly the living creatures survived. One hypothesis is that marine microbes, coccolithophores and foraminifera evolved to absorb the catastrophic increase in carbon dioxide.
The Cenozoic is divided into the Quaternary period, or glacial period, and those before, the Paleogene and the Neogene period. Results obtained by drilling of the floor of the Arctic ocean revealed the climate change during the past 55 million years in the Arctic. It has been cooling down over the past 55 million years, especially 45-25 million years ago, a large area of the Earth has cooled because concentration of carbon dioxide in the air dramatically decreased. This is the boundary between the Paleogene (65-23 million years ago) and the Neogene (23-2.5 million years ago).
The Indian continent collided Eurasia continent, the Arabian Peninsula collided Turkey, Africa approached Europe. The Himalaya and the Alps mountains began to uplift 15 million years ago. There was also a large volcanic activity. The gigantic mountains retained glaciers and contributed to the cooling by the albedo effect. In addition, due to rapid erosion, calcium ions flowed into the seawater and carbon dioxide in the atmosphere decreased. This is also one of reasons of the global cooling.
The Indian continent moved extraordinary fast. It has been moving 20 cm each year. The Australian continent is several cm every year, and the Pacific plate on which the continent does not ride is also about 5 cm each year. The Indian plate carrying the Indian continent has sunk under the Eurasian Continent. Fifty million years ago, the Indian continent collided the Eurasian Continent, then the sea floor, which was in front of the Indian continent, was pushed up onto the plate in the form of a ride over the Indian plate. This is the Himalayas mountains. The lifted part of Eurasian continent forms Tibetan Plateau. The Indian plate sinks into a vast Ganges plain with low altitude.
Antarctica was at the southern end of Pangea supercontinent, but covered with green plants long ago. An ocean current flowed with the Tasmania island about 35 million years ago, and Australia gradually separated from the continental mass of the south Pangea. About 30 million years ago, Antarctica arrived at its present position, and the Drake Strait was formed between the Continent of South America, which had contacted at the last. As a result, a cold current of ocean, called Antarctic Currents, formed around the Antarctic continent, which keeps warm current away from Antarctic continent. Forests remained in Antarctica until 25 million years ago.
A deep ocean current was formed from Antarctica to eastern New Guinea 15 million years ago. This deep current conveys cold seawater to throughout the Pacific Ocean, which resulted in cooling down the entire Earth. Antarctica froze as it is now, a thick ice sheet developed. The ice sheet covered the whole land 9 million years ago. The development of the ice sheet and the cooling of the global environment after 5 million years ago proceeded at the same time. The thickness of the ice sheet covering Antarctica reaches 4000 m. Due to the formation of ice sheets in Antarctica, the sea level of the world fell about 70 m. Also, the Antarctica continent sank 500 meters by the weight of the ice sheet. The huge ice sheet in Antarctica affects the global environment as a source of cold heat.
Angiosperms are divided into monocotyledons and dicotyledons. The origin of dicotyledons seems to be older.
Monocotyledons have the strongest reproductive power in plants. The gramineae family is well known. Its speed of photosynthesis is also great, growing fastest if the environment is good. It is generally an anemophilous flower. It forms grasslands in areas where precipitation is so small that forests cannot be formed.
Dicotyledonas are made up of a large number of species which are greatly different in form. There are various shapes, such as trees, flowers and vines. There are some strange plants with only leaves and roots like duckweeds. Most of them grow naturally, but some are parasitic like mistletoe. The world's largest flower Rafflesia is a family of violets, but it is a perfect parasitic plant. Their habitat environments are also diverse, ranging from desert cactus to water lilies and water hyacinth.
When classified roughly, monocotyledonous species do C4 photosynthesis. Even under the environment where the carbon dioxide concentration is lower, they grow faster than the general C3 type photosynthesis plant, and are strong against drying. C4 plants appeared around the late Cretaceous and rapidly increased 7 million years ago when the atmospheric carbon dioxide concentration became low. Since 2 million years ago, the glacial period with low carbon dioxide concentration started. They became dominant in temperate areas.
Since the end of the Tertiary, the Earth has cooled down and cold winter has come to visit, so annual plants prosper. Annuals do not have hard stems, growing according to the season, leaving a large number of seeds before the winter, their body withers in the winter. In the cold winter, they spend as seeds living long time.Therefore, generation change is fast. In addition, deciduous trees drop leaves in autumn and finish production activities and overcome the cold winter. This was also a consequence of adapting to cooling, and it was a way of life not existed in the Earth until then. The major extinction in the past is always caused by cooling, and the greatest adaptation strategy for plants against cooling may be an annual plant. Insects that live in temperate regions also produce eggs and pupas to be resistant to cold. They live one generation in a year.
As a result of the uplifting movements of each continent, plateaus and plateaus expanded within the continents. Around 5 million years ago, cooling progressed. A dry climate prevailed in the interior of the continent, and C4 plants of the grass family developed. Grasslands formed on the continent. A new breed of herbivores developed that adapted to these grasslands. The monkeys of our ancestors also emerged from the arboreal life of the forest into the grasslands and began to walk on the ground on two legs. In Africa, 3 million years ago, along with cooling, climate change increased and drying progressed. At the same time, the plains slowly switched from forest to grassland. It coincides with the emergence and prosperity of primitive man.
About 10 million years ago, high-temperature mantle material slowly rose just under the eastern part of Africa, thus the African continent began to split. The African Great Rift Valleys is a ridge that appeared on land, The valley penetrates the east side of the African continent in two rows from the north to the south. The end of the north turns into the Red Sea, heading to the Mediterranean Sea. The Africa continent is still breaking to the east and the west on the boundary of this Great Rift Valleys, and earthquake activity and volcanic activity continue in the vicinity of the Valleys.
The rift valleys can be seen in the Death Valley in the United States of America. Death Valley, Salt Lake of Djibouti in East Africa and the Dead Sea of Israel are lower than the sea level, and a lot of salt is deposited in the bottom of the valleys. Several million years later these places will become the sea.
The oceanic plate moves slowly, but recently, over the past 1,000 years, the rotation of its engine has fallen by a third. Two slowdowns were revealed, 13 to 12 million years ago in the Pacific Ocean, and 7 million years ago in the Atlantic and Indian Oceans. When the volcanic activity at the ridge weakens, the height of the ridge becomes lower. This resulted in the decrease of the sea level of 22m down. The reduction in heat release from the ridge was equivalent to 1,500 nuclear reactors.
Twelve million years ago, the collision of continents not only created mountain ranges such as the Alps, but also created a giant lake in the center of Eurasia. Its name is the Paratethys Sea. The Paratethys Sea stretches from the Alps at east to Kazakhstan at west. It was larger than the Mediterranean Sea. However, in 5 million years, its area has been reduced to a quarter, and the water level has fallen by 250m. Today, it remains in the Black Sea, Caspian Sea, and Aral Sea.
The arid plains became vast grasslands, and many large herbivorous mammals evolved. Among them, the ancestors of antelopes and goats were found on the north coast, and the ancestors of elephants and giraffes were found on the south coast. The giant lake also gave birth to the ancestors of whales. During the dry period (8.75-6.25 million years ago), the lake dried up, and these herbivores fled south to Africa. Between 6.9 and 6.7 million years ago, the southwestern tip formed an exit to the Mediterranean Sea. Its location was the bottom of the present-day Aegean Sea. The waters of the Paratechys Sea flowed into the Mediterranean Sea, and the Paratechys Sea disappeared.
The Gibraltar Strait connecting the Mediterranean and the Atlantic Ocean is a shallow strait with a width of 20 km and a depth of 200 - 400 m. Due to global declines in the sea level and crustal deformation in about 5.6 million years ago, the Gibraltar Strait changed to the land. Iberian Peninsula and Morocco were connected, and Mediterranean became a lake. This era is known as the Messinian salinity crisis. During this period, Mediterranean seawater evaporated on a large scale. Gypsum and rock salt, called evaporative rock, are found in countries such as Spain, Italy, Greece and Tunisia on the Mediterranean coast. The layer of gypsum and salt continues to the Mediterranean sea floor. It was proved in the research project of the deep sea drilling program of the seabed in the Mediterranean.
About 5.3 million years ago, the water came back again to the Mediterranean, but the details of this greatest flood of this Earth's history are only roughly understood. Drilling survey, seismic wave data, and research using numerical model suggested that this was a drastic change. It initially started with a small stream lasting for thousands of years, but 90% of the Mediterranean water flowed in less than two years. Such a sudden flood may make the sea level rise at a peak rate of over 10 meters per day in the ancient Mediterranean.
The uplifting movement on each continent has resulted in rapid cooling down from about 5 million years ago when highlands and plateaus spread within continents. There are currently two theories proposed as a cause of this.
One is the formation of Panama land bridge. The deep water that was flowing from the Atlantic to the Pacific Ocean was blocked by this bridge. And the Mexican gulf stream became largely to flow to the north. The warm Mexican gulf stream increased the amount of snowfall in North America. The ice sheet was expanded when it was cold to amplify the cooling. Greenland was a green island as it was named before, but it turned into an island of glaciers.
The second is the formation of the Himalayas and the Tibetan Plateau. These topographical elevations disrupted the atmospheric circulation of the Northern Hemisphere. The monsoon climate has been established mainly in India and strengthened the Siberian cold weather in winter. This is a hypothesis that it caused cooling.
As the average temperature decreases, the amount of water vapor contained in the atmosphere decreases. That is, the amount of water carried into the land by the atmosphere decreases. Because the water is not carried to the interior of continents, the central part of continents becomes dry. In general, cooling is drying, warming is moistening. Global cooling expands grasslands and desert, whereas global warming expands forests. Although contemporary global warming and desertification are often discussed on the same stage, the commonality of both is the result of human activities. The desert would shrink as global warming progresses without human activities.
A dry climate spreads in the inside of the continents, there are also development of plants of the grass family just so that the continents have large grasslands. And a new kind of mammal adapted to such grassland has evolved, such as ancestors of dogs and wolves, and horses. Monkeys of an ancestor of mankind also went out to the grassland from the tree living of the forest, and walked on the ground with two feet. Tweet birds, called songbirds, developed greatly. It seems to be a driving force that dominated communication by singing voice, agile exercise ability.
Cenozoic terrestrial volcanic activity is well investigated. The volcanic territory of Yellowstone National Park moved from Oregon to Wyoming during 16.5 million years. This is because the North American continent has moved westward over the hotspots. Large eruptions in Yellowstone National Park occur approximately once every 1.5 million years. The largest ones are the Idaho eruption 8.7 million years ago, followed by the large eruption 2.1 million years ago. Since they were about the same scale as the eruption of Toba volcano 74,000 years ago, it should have been accompanied by a temporal cold climate of several years.
From 2.6 million years ago to the present, the glacial and the interglacial time have been periodically replaced. This time is called as the quaternary period. According to survey of the ice sheet on Greenland, the cycle was about 40,000 years from 2 million years ago to a million years ago, and from a million years ago to the present, the cycle was about 100,000 years. When analyzing the cycle, several waves are overlapped. Several external factors are considered to affect the climate change, by changes in solar radiation amount, due to the change of distance between the Earth and the Sun (100 thousand years period), changes in the inclination of the Earth's axis (period of 20 thousand years and period of 40 thousand years). However, changes in temperature, ice sheet volume, etc. are larger than those changes. Changes in solar radiation amount are thought to have been amplified due to air, ocean and continental arrangements, topography, and so on.
Loess began to accumulate in China in Loess Plateau from about 2.5 million years ago, most of which began in the quaternary period which started about 2 million years ago. It is estimated that the uplifting of the Tibetan Plateau would block the atmospheric circulation from the tropical zone and that the inland parts of China would dry out.
Glaciers widely covered the northern part of the northern hemisphere during the heyday of the glacial period, and a massive flood occurred due to the breakdown of the glacial lake every time the interglacial age. In the bottom of the Dover strait, there are evidences that devastating floods occurred twice, 400,000 years ago and 200,000 years ago. Due to the large flood, Britain Island would have been separated from the continent.
The last glacial period started 130,000 years ago. It became gradually cool with some fluctuation since then, until 18,000 years ago. The temperature rapidly rose from the glacial period to the modern interglacial period, because warming was accelerated as the glacier began to melt. It is estimated that rapid warming occurred as well as 130,000 years ago.
Changes in the global environment in recent years since the Industrial Revolution are comparable to catastrophes in the past. Since this environmental change is attributable to human activities, a new period classification of Anthropocene (Fifth century) named after Anthropogenic (by human activity) has been introduced in fields not related to classical geology. This time classification, the definition does not depend on the strata. The basic idea is the same as the classification of the geological age is decided by the annihilation of the species recorded in the strata and the large-scale change of the global environment.
Before entering the evolution of mankind, I will summarize the history of the Japanese archipelago in two parts.
Among the rocks in the Japanese archipelago, the oldest is located in Kitakami Mountains in Tohoku district, or Hida mountains. It is thought that these rocks were not the accretionary prism but were accumulated in the shallow sea. It probably accumulated in the north side of the Gondwana continent before the Bariscan orogenic movement, and on the Panthalassa side of the China-Korean subcontinent. Estimated from the Paleozoic fossils included, it located in the southern hemisphere near the equator.
The origin of the limestone caves in Japan dates back to the Paleozoic era. The limestone body of the stratum contains fossils of Sea lilies and Fusulina, which are indicator fossils about 300 million years ago. The huge limestone body that creates limestone caves extends from Kanto to Tokai, Kii, Chugoku and Shikoku to the central part of Kyushu. The limestone body originates from coral reefs developed in the far south ocean. It is located on the basaltic sea mountain on the sea floor. The submarine volcanos that were born at a hot spot on the Pacific Ocean had moved northward by the movement of the Pacific plate. Coral reefs and submarine volcanoes are considered to be accretionary bodies that detached from the ocean plate and accumulated at the plate boundary.
The growth process of accretionary complexes in the Chugoku and Shikoku districts has been elucidated. The stratum on the Sea of Japan side is an accretionary complex of about 300 million years ago. Going south from there, the age of the strata becomes newer, with accretionary complexes younger than 200-150 million years old in the Setouchi region and 80 million years old in southern Shikoku. Over 300 million years, the continent has grown 450 km towards the sea. It is estimated at 150 km in 100 million years.
In Mesozoic era, from Jurassic to Cretaceous periods, strata were formed around the bodies with sediments flowing from the continent of that time. They were taken in the Japanese archipelago formed later and appeared on the ground due to crustal deformation.
It is in the midst of the Cenozoic period that the Japanese archipelago started to be formed like the present shape. The Japanese archipelago up to about 30 million years ago was located in the east edge of the newly created Asian continent, and there was no intense fluctuation. Two inland bays were present at a position of present Kyushu and Hokkaido, and plant fossils were deposited there. Most of Japan's coal was made of at this age. Inner Bays are a sign of the Japan Sea. Adducts from the Pacific plate were accumulated at the Sea near the continent.
The Pacific plate came a long distance thus became cold and heavy. Thus, it would sink at a large angle. The plate dragged in the continental margin, a small rising flow of mantle occurred inside the continent. As a result, the continent was stretched and torn. About 25 million years ago, the edge of the continent began to tear, and around 22 million years ago, a huge fault activity occurred across East Asia. It is believed that the Sea of Japan started expanding from one point and split in three directions. Two of these fissures form the ocean floor of the Sea of Japan, and the other one forms Fossa Magna without becoming an ocean floor.
The northeastern and southwestern parts of the Japanese archipelago swollen toward the Pacific Ocean, with western Japan rotating clockwise and eastern Japan rotating counterclockwise. The bent portion was pulled to either side and sank, becoming Fossa Magna. Fossa Magna is a large trench found on the east side of a large fault called the Itoigawa-Shizuoka Tectonic Line, which is filled with sediments.
The same phenomenon was occurred between Australia and New Zealand. A drowned continent Jealandia is supposed, and at the edge of Jealandia again uplift occurred, New Zealand and New Caledonia were formed. Similar terrain is found in Kamchatka Peninsula, Taiwan, and Philippine Islands.
Around 19 million years ago, a big fault was formed on the side of the Japan Sea and the ocean entered into the rifts. At the same time the eruption of the submarine volcano began. The activity of the volcano was very active, lava and volcanic ash spread throughout the region and accumulated in large quantities. Eventually the lowland expanded, the Japan Sea formed. The living organisms and fossils of dinosaurs that lived on the continent came to the Japanese archipelago on the edge of the continent.
The Philippine Sea plate was born as a result of a new plume 52 million years ago. It expanded northward, began to subduct from the Ryukyu Trench, through the off coast of Shikoku, then reached the Ogasawara Trench in 20 million years ago. As a result, the volcanic islands that were in the border between the Philippine Sea plate and the Pacific plate have been added to the central part of Japan from 14 million years ago. In addition, due to this change, a large amount of magma was supplied to the basement of western Japan, the caldera volcano was active, a large amount of granite was made under the western Japan which uplifted the mountains.
Because the Philippine Sea plate was blocked northward and the direction of its movement changed, East Japan was pushed by the Pacific plate westward and started uplift three million years ago. The ocean floor from Hokkaido to Kanto became mountain ranges till the present. The northeastern and southwest parts of the Japanese archipelago moved toward the Pacific Ocean. East part of Japan moved in a clockwise direction, and East Japan rotated in a counterclockwise direction. The bent portion was pulled on both sides and settled, and it became Fossa Magna.
The Pacific plate has been driven down below the North American plate near Hokkaido, and the Kuril islands were formed at the top of the subduction zone. Below the Eurasian plate in western Japan, the Philippine's Sea plate was driven down, where the Ryukyu archipelago was formed. The Pacific plate was driven under the Philippine Sea plate and the Ogasawara Islands were formed.
The Pacific plate subducted below East Japan, a trench extending from north to south was formed, and in parallel to it, wrinkles of earth in the north and south direction were formed. A series of outer arc uplift zones were formed on the land on the side of the trench, that is, a mountain range. A central lowland was formed on the west side of the mountains, further west side, a volcanic front and inner arc ridge were formed. The volcanic front is formed just above the magma where the Pacific plate sunk into the mantle and melted. Volcanic activities began several millions years ago and reached the peak in the period from 2 million years ago to one million years ago. Outer arc uplift zone consists of old Mesozoic rocks, volcanic front and inner arc ridge consists of igneous rocks from 23 million years ago to 5.3 million years ago.
Under the western Japan, the Philippine Sea plate subducts obliquely to form the Nankai Trough. This movement of the plate has made a huge lateral fault (Median Tectonic Line) at the part corresponding to the outer arc uplift zone. On the north side, the Seto Inland Sea exist, which corresponding to the central lowland, and further north side, the inner arc ridge and volcano front are formed and it reaches the Japan Sea. The volcano front is far from the Nankai Trough because the subduction angle of the Philippine Sea plate is shallow. Since the plate sinks diagonally, wrinkles of earth are obliquely formed in the outer arc uplift zone, and there are large peninsula and basins between them. Wrinkles of earth also occur in the central lowland, forming a large basin (Nobi Plain, Lake Biwa, Osaka plain) and several open sea in the Seto Inland Sea.
The current Japanese archipelago is located where the land masses on the Eurasia plate heading southeast collide with the Pacific plate moving towards the west. Meanwhile, the North American plate and the Philippine Sea plate are sandwiched. The North American Plate and the Pacific Plate are in contact with the Tohoku from the Kanto to the Pacific Ocean facing the Kuril Islands, forming the Japan Trench. The North American plate moves from the northeast direction to the southwest direction. Both the North American plate and the Eurasia plate have a land mass, and they do not fall inside the earth at the point where they hit. The area around the Kii peninsula is extruded in the southwest direction by the North American plate.
On the east side of Fossa Magna, the Philippine Sea plate is subducting from the south. The islands of the Izu-Ogasawara arc, formed where the Pacific plate can get in under the Philippine Sea Plate, came to Japan on the Philippine Sea Plate at the position of the Izu Peninsula. The landed lumps of old ages were Tanzawa mountain clumps and the Izu peninsula. They had pushed the land to from winkles of earth such as the northern, central, southern Alps and Yatsugatake mountains. The next islands to hit will be Oshima and its surrounding islands. It is said that a peninsula will be formed of the size of Nagano prefecture in 10 million years,
The Boso Peninsula is at the intersection where the two plates are submerged. Thus, from Boso peninsula, two outer arc uplift zones are erecting and a huge central lowland (Kanto plain) is made. The reason why the Kanto Plain did not become the sea is thought that a large amount of earth and sand was supplied from many rivers.
Hakone is volcanic area that has been active since 600,000 years ago. Fuji was formed by eruption several times from 100,000 years ago. The volcanic group of the spine of the Tohoku region and the volcano group of the San'in region started from several millions years ago and reached the peak in the period from 2 million years ago to one million years ago. Several volcanoes consisting of a huge caldera have erupted in Kyushu since one million years ago. In the southern Kyushu region, the topography from Mt. Aso to Kirishima to Kinkou Bay is a giant caldera assembly. Aira caldera on the north side of Kinkou Bay erupted about 30 thousand years ago. The most recent caldera eruption was the Kikai caldera in the southern part of the Kinkou bay, 7300 years ago. With this massive eruption, the living organisms in the southern Kyushu area have been extinct. Large caldera-type eruptions are expected to occur in the future, and southern Kyushu will continue to expand toward Yakushima islands.
The Shatsky Plateau, the second-largest known volcanic activity in history, approaches 1,500 km east of the Tohoku region of Japan. The expansion rate of the East Pacific Ridge is calculated to be 18 cm per year, and if this rate continues, it will collide with the Japanese archipelago in 8.3 million years. The Shatsky Plateau is 1.2 times the size of Japan and rises 5,300m above the seabed. In eight million years, the area of Japan may double.
The anthropoidea of the old world appeared in the Africa continent then entered into the Eurasian Continent. The oldest fossil of an ancestor of a primate is about 65 million years old (late Cretaceous period). About 30 to 25 million years ago, the anthropoidea were divided into two groups, old world monkeys including Japanese monkeys and hominoids including apes and humans. Old world monkeys and hominoids live in groups. From the fossil record, the hominoids were prosperous at the beginning, but the proportion of the old world monkeys increased after about 10 million years ago. Currently nonhuman hominoids (ie apes) are on the verge of extinction.
In mammals in general, the main sense is olfaction, but in primates it changed to vision. For example, in mice, the odor receptor gene family has 1391 genes, of which 328 are pseudogenes. In human, there are 802 odor receptor genes, of which 415 are pseudogenes. In primates the opsin gene were duplicated and their sense of vision to red and orange became better. Communication between primates also changed from smell to vision. Besides primates, mothers and children recognize each other by smell. The vision became important and the expression of emotion was developed in the primates.
The primate's ancestor lived on the tree. The movement and tactile sense of hands in the primates developed and adapted to arboreal life. The thumb was opposed to the rest of the fingers, which makes primates able to grasp. The muscles necessary for movement of fingers are also sensory devices of movement. Animals feel the extent of muscle's elongation and the contraction speed, so they inform their brain how much the finger is bent and how far the fingertip is spreading. Eyes of primates came to the front of the face. The visual information from the eyes passes through the brain, the command goes to the muscles to move the fingers, and prepare the fingers to move. A monkey instantly recognizes whether the grabbed branch is sufficient to support its weight or not, how about the deflection, and takes appropriate action. Brain and hand functions co-evolved.
Another difference between primates and Old world monkeys is the presence or absence of a tail. There is a tailless mutant in mice, and an associated gene has also been identified. The tail is also an important locomotory organ for Old world monkeys. Genetic clocks estimate that the ancestors of primates lost their tails 25 million years ago.
There are some abilities and properties that are thought to have been acquired in the monkey era (incorporated as genes). Use of simple tools, group life, ranking in herds, skincare such as grooming in herds, fear of certain things.
Old world monkeys also use tools as extensions of the hand. In order to use a tool, we need the muscles of the hand, the skeleton that supports the hand, the vision that observes changes in objects, and the brain that controls harmonious behavior. Individuals with dexterous fingertips and the ability to control their power were advantageous for feeding on insects underground and in decaying trees.
Needless to say, sociality in Old world monkeys is a subject of extensive research. Phobia can be divided into four distinct categories. 1. Fear to animals such as snakes, spiders and scorpions. 2. Fear to the environment such as high places and dark places. 3. Fear to blood, corpses and injuries. 4. Fear to dangers such as being trapped in a small space. These were programmed to survive.
Upright bipedal walking and shrinking of cuspid teeth are characters separating apes from human beings. Human and chimpanzee brains are not very different anatomically, other than size. Comparing the chimpanzee and human genomes, they are 98.5% homologous. However, when only 6000 promoter segments were examined, the difference was about 10%, and the differences were concentrated in genes related to brain function and nutritional intake. 49 human accelerated regions (HARs) have been identified that are presumed to have changed after chimpanzees and humans diverged, but their association with genes related to brain function remains unclear. HAR itself does not code for a protein.
Bipedal locomotion has been evolved in arboreal life. Orangutan seems to be a direct descendant of a monkey who walked two legs in arboreal life. Some of the muscles required for upright bipedal locomotion are also required for arboreal living. Among our tree-dwelling ancestors, there happened to be one with a pelvis suitable for bipedal locomotion. Such individuals were rather restricted in arboreal behavior, but were advantageous in foraging activities on the ground. Primates remained in a sparse forest with no canopy, evolved into gorillas and chimpanzee, which moving up and down in the space in the forest. On the other hand, primates who live in savanna evolved into pithecanthropus (8-5 million years ago). Gorillas and chimpanzees changed from bipedal walking to knuckle walking, but the pithecanthropus did not do knuckle walking.
Using the mutation rate revealed by genome analysis, the species branching age between homo and chimpanzees, gorillas, orangutans were estimated as 6 to 7.6 million years ago, 7.6 to 9.7 million years ago, and15 to 19 million years ago, respectively. Similarly, the effective population size (number of individuals) in the ancestral line corresponding to these species branches was 59,300 to 75,600, 51,400 to 66,000, and 159,000 to 203,000, respectively. The branch ages estimated from their genome sequences are in good agreement with the age of fossils of human ancestry that has been known hitherto.
It was suggested that the large ape, Nacalipithecus, who lived in Africa about 10 million years ago, are common ancestors of humans, chimpanzees and gorillas. Similarly, Fossil of Sahelanthropus was discovered from the strata of seven million years ago. Saheranthropus's brain volume is similar to gorilla, it is only about 350 g. Only skulls have been found, but the shape of the face is like human. It is thought that Saheranthropus is just before or just after the branch of human - chimpanzee species. Aldipithecus (5.2 - 5.8 million years ago) is considered to be the oldest human immediately after branching of human - chimpanzee, typically the Australopithecus Ramidas is well known.
The eastern part of Africa about five million years ago was much more rain than it is now, covered with humid forests. Many apes were living in groups. Gorilla makes a harem. In contrast, chimpanzees live with multiple females of male. Southeast Asian apes, orangutans and gibbons, live alone. Since the direct ancestor of hominin cannot be found in Southeast Asia, Australopithecus is expected to live a social life of African ape type. African apes had an arboreal living and are good at climbing trees. There are few foreign enemies on trees, which seems to have been on near the top of the food chain.
The African Rift began to form around 30 million years ago, but uplift and drying occurred in the last 3 to 4 million years ago. At the same time, the Himalayan mountain-building and the closure of the Indonesian sea route dried up East Africa. East Africa has transformed from flat land covered in tropical forests to rugged mountainous terrain with plateaus and deep valleys, with vegetation ranging from cloud forests, savannahs to desert scrublands. A mosaic environment was appeared of forests and grasslands, ridges, steep cliffs, plateaus and plains, valleys, and deep freshwater lakes at the bottom of the Great Rift Valley. Forest habitats slowly fragmented, that provided diverse food sources, livelihood resources and opportunities for our ancestors. Australopithecus then diverged from tree-dwelling primates. At the same time, rapid environmental changes allowed early humans to survive longer, evolving tool-using brains and intelligence, made them versatile and adaptable.
The first ape having a completed upright bipedal walk is the famous fossil Australopithecus aforesensis called Lucy (3 - 4 million years ago). Her brain is not so large compared with an ape, and the volume was about 450 cc.
Characteristic cuts remained in the mammalian bone of 3.4 million years ago found in Ethiopia. It is reported that this is the earliest evidence that Australopithecus used stoneware. However, stoneware has not been found in the same place. Likewise, in Ethiopia stoneware from 2.6 to 1.5 million years ago was discovered along with the bones of animals. It is called Ordwan Stoneware. This stoneware was created by Australopithecus Habilis (also called Homo Habilis).
There are mainly two kinds of Hominina. One is a spindly type (homo genus) and another is a muscular type (Paranthropus genus). The Australopithcus has disappeared as fossils since the Paranthrhophus genus appeared around 2.5 million years ago.
The genus Paranthropus was larger and had hard grinding teeth compared to the genus Homo. Also, Paranthropus seems that the power of the jaw was strong as the cheek bone was developed. It was advantageous for ingesting hard plants with a lot of fiber. Fossils of the head of Paranthropus Robustus were found in the cave of Swartkrans in South Africa. Animal bones of 1.8 to 1.2 million years ago are also found in this cave. It is presumed that this cave is a living place of carnivorous animals where captured preys were drawn in and eaten. Heads of Paranthropus were left to become fossils, because they were hard to eat. Paranthropus coexisted for a while with Homo that appeared almost at the same time, but it was extinct about one million years ago.
It is thought that about 2 million years ago that the Homo genus, the current human strain, appeared. The fossils of the oldest original people were discovered from the stratum of 2.2 million years ago. Homo genus developed to the same size as the modern person. A mother gave birth to a child as immature state, which showed secondary late maturation that the brain develops even after birth.
The rewarding nerve affecting a wide range of the brain is called dopamine pathway. It extends from the midbrain as the base point to enter the hypothalamus. Here, the intensity of pleasure of appetite, sex will be determined by the amount of dopamine released by the nerve. Next it extends through the amygdala in the limbic system, some extend to the mesolimbic system, the rest reach the frontal association area. It is said that the dopamine pathway covers important parts for human mental activity, and human pleasure is brought about by the dopamine pathway.
Human being is born in the state that he/she needs the 100% protection from his/her mother. Although this is disadvantageous in survival, growth of the brain after birth produced plastic intellect and eventually succeeded in survival. If child's maturation took time, it seems that children's education became a joint work of father and mother, so human sexual bond was fixed in the early history. In a slightly expanded interpretation, children's education has become more important as a group's collaborative work. In contrast to apes, the male would never fight over sex, sex would be privatized, and the group's cooperation system might have been enhanced.
Hominina evolved in Africa continent, but spread over Eurasia continent 1.8 million years ago. Homo erectus has also been found at the east end of the Eurasian Continent as Homo erectus pekinensis, Pithecanthropus erectus (Java) etc. However, it has not arrived in Japan. Perhaps there was no ability to cross the strait sea. Besides, a small human being of 1.8 million years ago was discovered in the Republic of Georgia and is called Homo erectus georgicus. The shocking finding is Homo floresiensis found in Flores Island in Indonesia. Its height was less than 1 meter and its brain volume was only 420 cc. Bones of from 90,000 to 18,000 years ago have been found.
Homo erectus can spread over Eurasian Continent thanks to rock salt scattered inside the continent. The way of salt is the rope of life. There is no human survival without it. The belt area of Northern latitude of 40 - 50 degree produced rock salt in Eurasian Continent. Homo erectus could not spread to cold regions such as Siberia.
Understanding of a human infant about the movement and so on of the object is similar level to that of infants of chimpanzees and orangutans. However, human comprehension skills in infant are much better than those of apes. Social ability is to learn from others and to understand what others know and do not know.
Characteristics of the Hominin are significant brain enlargement. Brain upsizing accelerated around 2-1 million years ago. The size difference between the macaque and human brain is 10 times. Considering the developmental process of the brain, if the proliferation period of the progenitor cells is longer by three days, the brain becomes 10 times larger. Human brain has more nerve connections than other mammals, so the brain becomes larger.
Human brain enlargement is observed in the fetal stage. It is characteristic of humans that brain volume continues to grow until the late stage of fetal life. This is not seen in apes such as chimpanzees. Furthermore, in Homo sapiens, the brain grows after birth. The maximum brain volume before birth is determined by the size of the birth canal of the female or the opening of the pelvis. The newborn skull up to 400 cc can only pass it. The volume of 400 cc is the size of the skull of an adult chimpanzee.
Why did the human brain grow in size? The candidate gene is NOTCH2NL. The NOTCH family is a group of genes that induce differentiation during development. NOTCH2NL is a gene unique to humans by comparing the genomes of mice and chimpanzees with humans. 14 million years ago, A part of the NOTCH2 gene was copied to the long arm of chromosome 1 (ape type). However, this incomplete gene was repaired to become a functional NOTCH2NL gene 3-4 million years ago. After that, the NOTCH2NL gene was duplicated to 3 genes at last. The NOTCH2NL gene is strongly expressed in the human fetal brain and also in the nervous tissue (organoid) made from iPS cells. Duplicate genes are evolutionarily unstable and are prone to deletions and duplications. Scientists are investigating whether hereditary neurological disorders are associated with the NOTCH2NL gene.
The larger brain needs a lot of energy. The cultural difference between the monkey and Hominin is the use of stoneware and carnivorousness. That is, crush the bones to eat bone marrow and brain, which other carnivores have left behind. Later Hominin used processed stone tools and left evidences using fire. Although there is the theory that enlargement of brains has come to eat meat, the carnivorous animals do not necessarily have big brains. It is thought that having a hand that can hold a tool promoted the development of the brain. Another hypothesis is that the genus Homo started using fire two million years ago and succeeded in nourishing the brain by ingesting carbohydrates and enlarging it. In any case, the graph of brain volume started up 2 million years ago.
The three most recent epochs of extreme climate change occurred 2.7 to 2.5 million years ago, 1.9 to 1.7 million years ago, and 1.00 to 900 million years ago. Fossil records suggested that the emergency of new species of early humans and the extinction of older species coincided with these epochs of dryness, humidity, and temperature. It is thought that the epoch of change not only influenced human evolution, but was also the driving force behind the migration of some species of the genus Homo to the Eurasian continent. The most dramatic expansion of the brain occurred between 800,000 and 200,000 years ago, coinciding with repeated ice ages.
In the past millions of years, the glacial period repeatedly arrived at a cycle of 40,000 to 100,000 years. Especially, the period of 100,000 years appeared predominantly from 800,000 years ago. The history of the climate cycle is preserved in the deep sea as sediments. It is also recorded in Antarctic glaciers in the past 200,000 years. The isotopes of various atoms in samples excavated from glacier of the Antarctica and rocks in the sediment are examined to determine the temperature of atmosphere. A commonly used isotope is the oxygen 18. Examining content of O18 in the sediment at the bottom of the ocean, it is cold if the ratio of concentration of O18 to that of O16 becomes higher, and it is warm when the ratio becomes lower. It is opposite in the case of the glacier. The amount of O18 relative to O16 contained in ice and snow increases as the temperature rises. The marine oxygen isotope stage (MIS) is a basic memory for discussing paleoenvironments. There are over 100 stages covering 2.6 million years.
Mathematical analysis divides the cycle of isotope fluctuation into three kinds of waves, which are related to the fluctuation of the orbit of the Earth. It is general that not only in the Earth, there are three elements in the planet orbit; eccentricity, inclination angle of the Earth axis, and precession movement.
Eccentricity is a numerical value that represents the extent of the ellipse of the Earth's orbit. The distance between the Earth and the Sun changes in accordance of eccentricity. The eccentricity variation has a period of about 400,000 years and about 100,000 years. The inclination angle of the earth's axis is the angle between the axis of the Earth and the orbital plane of the Earth, and varies from 24.5 degree to 22.1 degree with a period of 40,000 years. When the inclination angle is large, the solar radiation is strong in the summer and weakens in the winter, that is, the seasonal change increases. Precession is a swinging motion in which the tilted axis slowly rotates. It will make a lap in about 23,000 years. In half of the time, summer and winter will be reversed.
These changes only slightly vary in day time and angle of sunshine. However, the changes in greenhouse gases (carbon dioxide, methane, etc.) due to biological activity, the albedo effect by glaciers (rearrangement of continents) result in enhancement by positive feedback to fluctuate the average temperature. The air composition in the glacial bubbles of Antarctica was examined on a large scale and it was shown that the concentrations of carbon dioxide and methane in the atmosphere correlate well with changes in temperature.
As the name suggests, the glacial age is the era when glaciers exist on land. As the glacier developed, water moved from the sea to the land. The coldest period of the ice ages is called the glacial period. The range of fluctuation of the temperature slightly increases since 500 thousand years ago, the glacial period tended to become longer. The last three glacial periods are the Mindel glacial period (300 to 230 thousand years ago), the Riss period (200 to 130 thousand years ago), and the Ulm glacial period (70 to 12 thousand years ago). Meanwhile, the sea level decreased by about 100 m. In the vicinity of the pole, the land where the living creatures were able to live becomes narrower, and the land increased near the equator. Also, it seems that the salinity concentration rose by the amount of seawater less. For terrestrial organisms, temperature and vegetation may have been promoting species differentiation due to the relatively short period variation, as the same, salt concentration may have been for marine organisms.
The temperature variation graph shows that the present age is the interglacial period. The present warm interglacial period ends in at most 10,000 years, after which the glacial period arrives in about 70 thousand years.
In the classification, the genus is above the species, and the family is, then, the order. There are 180-200 species (so-called monkeys) in the order of primates. Among them, there is only one species of Homo sapiens in the family Homo. Obviously, it is abnormal. Only the homo sapience cannot have made any special evolution exceptionally in the family. Like in other families, many genera and species were born, but it is thought that everything was destroyed.
The nature of departing from home and to the world seems to be one of features of humanity. Apes survive in the fixed place of the jungle and will not move to look for new habitats. Hominina who left Africa more than 1.8 million years ago immigrated to Eurasia continent promptly, from Flores Island (Indonesia) at far East to Spain at far West, where is tropical or Mediterranean climate. From a few fossils and archaeological evidence, Hominina lived primarily in a temperate climate. It was exceptionally only warmer period that the Hominina went beyond 45 degree line of the north latitude.
Homo erectus was born in Africa 1.9 million years ago and left Africa to enter Asia. They reached Java 1.6 million years ago, which was connected to Asia. It was extinct 500,000 years ago in Africa and Asia. However, they lived on Java until 100,000 years ago.
Recent discoveries have found other humans, other than Homo erectus in Southeast Asia. Small human Floresiensis found on the island of Flores, Indonesia. H. luzonensis was also found on Luzon Island in the Philippines. Floresiensis had survived till 20 thousand years ago, but it is thought to be Hominina from the structure of the wrist bone. Height is 1 meter, brain volume is only 400 cc, it is a size of Australopithecus. Therefore, the assumption collapses that the brain upsizing occurred in cooperation with the evolution of human beings, that is, the use of tools and sociality. There is a genetic disease called Microcephalic osteodysplastic primordial dwarfism type II. It is a mutation of the gene PCNT. Human being with this mutation has a small body and brain. Is Floresiensis a progressive Hominina with this genetic mutation?
The melanocortin receptor gene controls the proportion of melanin pigment in skin, which determines the color of the skin of hominina. When examining the silent mutation in the melanocortin receptor gene in current black peoples and applying it to the gene clock, it was fixed 1.2 million years ago. Melanocortin receptor gene mutation is thought to have spread over 120,000 years ago, that is, throughout the Hominina. Did the color of the black skin be chosen because their hairs became thin? Analysis is awaited of genes involved in dwarfing of body hair. On the contrary, the invention of clothes overcomes the temperate of freezing winter and became the basic technology crossing the glacier.
Traces of human beings using fire trace were found back to the Middle East of 790,000 years ago. Homonina used fire first. After this, traces of fire use were discovered about 500,000 years ago in China and about 400,000 years ago in Europe. To use fire is to have technology to control fire. There should have been knowledge and tools to obtain and maintain fire. The method of using fire that hominina invented was handed down to Neanderthals and modern people.
To use fire has various merits. Heating, cooking, light and weapon. Human beings could expand their settlements around the world due to the use of fire. There is the winter even in temperate areas. Fire would provide men a heating system to get over the winter. The technique to withstand the cold was also a technique that crossed over a highland which is a cold district. Furthermore, when heated, all microorganisms, such as bacteria, die. When boiling or baking, hard food also softens. In addition, it was heated to eat hard fruits and dried meat with high storability. Many foods found in unknown places could be edible by heating. It is unknown how the hominina got the fire.
Mankind has acquired digestible food by using fire. Their internal organs had shrunk and the energy used by internal organs had become to use for the brain. Human brain grows slower than brains of other mammals. The maturation of the body is also slow. There is a theory that body growth has been sacrificed in order to develop a brain with high energy consumption.
In the ruins of Grand Dolina 780 thousand years ago, evidences of cannibalism are found. In addition, the outrage is a routine matter in an undeveloped society. In a typical undeveloped society, 80% of tribes perform tribal conflicts more than once a year, and the deaths from battles are one in 200 every year. Moreover, there are many extermination fights. For early hominina, cannibalism may have even been a valuable source of food. In East Africa, a cradle of human beings, several species of Australopithecus and Hominia were inhabited together. I cannot think that they had mutual consciousness as a human being.
Human being closer to modern people appeared among Hominina remaining in Africa. Neanderthal people are famous. Genomic DNA was analyzed from the Neanderthal fossil bone, and at least 99.5% of the genome were found to be identical between the current human being and the Neanderthal. They branched between about 706,000 and 330,000 years ago from the ancestor of the present human race.
The Neanderthal people have slightly larger brain volumes than the current human beings, and the skeletons are almost the same. They produced a new stoneware technology. The Neanderthals are said to have lived in Europe and West Asia, but recently their fossils have been found in Uzbekistan and southern Siberia. A mixing between the ancestors of the present human race and the Neanderthal surely occurs, and a part of the Neanderthal genome sequences are found in the modern human genome. Modern people settled in Europe 45 thousand years ago. Analysis of 51 genomic DNAs from between 7000 and 45000 years ago showed that the Neanderthal DNA in the genome decreased from between 3 and 6% to 2% during this period. The Neanderthal people disappeared from the fossil record about 30,000 years ago.
Analysis of the hyoid bone of the Neanderthal people discovered from the Kebara cave in Israel suggests that the Neanderthals had the same speaking ability as us. The hyoid bone is a potential role in speaking and its position is adjusted by 12 muscles. The Broca’s area, which is the center of speech, is probably well-developed as estimated from Neanderthal brain volume. Between Neanderthal's DNA and current human beings have the same version of "language gene" called FoxP2. It seems that the Neanderthal people could talk with each other.
The genomic base sequence of an old woman excavated at the Denisova cave in the southern part of Siberia was examined using DNA extracted from the finger bones of the hand. From the shape of one tooth, Denisovan was suggested to be evolutionarily different from both Neanderthal and present human beings. The group to which the Denisova woman belonged has the same origin as Neanderthal. It is estimated that the Denisovan and Neanderthal ancestors diverged from today's humans 800,000 years ago. After that, the two humans separated, but the time is unknown. The characteristic base sequences of the Denisovans remains in humankind today and is found in the natives living from Siberia to Oceania. Mixed-race bones of Denisovans and Neanderthals have also been found.
The Denisova Cave was discovered in 2010 and is located at the foot of the Altai Mountains, the boundary of four countries, Russia, Mongolia, China and Kazakhstan. Humans began to live in the Denisova Cave 300,000 years ago, and judging from the stone tools, they were Denisovans or Neanderthals, and from 200,000 - 55,000 years ago, the cave was mainly used by the Denisovans. During this time, it seems that Neanderthals lived together 190,000 - 100,000 years ago.
Not only did mankind come out of Africa, there should also be a return group. In particular, the Middle East is the area of intersection of the going-out and the returning human beings. There is expected direct crosses and diverse cultural interactions. Genes from Neanderthals can be found in the African genome. There is no evidence that a new human race was born on the Eurasian continent. If it is all African origin, there will be some reason.
During the ice age 425,000 years ago, a vast lake was dammed between glaciers in Scotland and Scandinavia, and a 30km-wide rocky ridge that connected France and England. The water that overflowed during the interglacial period formed a huge waterfall and eventually caused the dam to burst. The rupture also occurred 200,000 years ago during the interglacial period between the Mindel Ice Age (300,000 to 230,000 years ago) and the Liss Ice Age (200,000 to 130,000 years ago), creating the Strait of Dover. Part of the former land bridge remains as the White Cliffs of England and France.
The direct ancestor of the modern human, Homo sapiens, was born in the Riss glacial period (200 to 130 thousand years ago). The birthplace was in Africa continent. In the glacial period, the tropical regions of Africa are thought to be dry. The tropical rainforest shrunk and was surrounded by spacious savanna. The desert expanded.
Naked modern human beings were unable to leave Africa for tens of thousands of years, during the Riss glacial period. Meanwhile, the modern human being was able to develop and maintain advanced technology compared to the other human being. Present human race invented polished stone tools. They also developed heavy stone instruments (such as axes) with fine workmanship, in consideration of stone quality. When they started agriculture, they developed stone sickles for harvesting grains, stone dishes, stone bowls, stone pestle for milling, and stone arrowhead etc.
The stoneware developed by the present human race is designed according to the application. They also used bones and ivory in combination. Perhaps they would have changed the design of the tool to match the ecosystem (such as prey animals and plants are, the geographical conditions of the hunt).
A phylogenetic tree based on mitochondrial DNA of modern people, one of the African branches is corresponding to other races, such Caucasian and Asian. When chimpanzee's DNA sequence is added as a reference to this phylogenetic tree, assumed that human and chimpanzee branched five million years ago, the common ancestor of the modern human beings is calculated to be about 200,000 years ago. Because the phylogenetic trees are made with the hypothesis of "branching", this alone is not enough for evidence of the time of birth. After Homo sapiens idaltu (about 160 thousand years ago) was found in Ethiopia, who had quite similar characteristics to the current human race, "African single origin theory" was almost confirmed.
Evidence was discovered that ancestors of modern human used coastal resources at the Sea cave near the Pinnacle Point in South Africa. It is 164,000 years ago. In South Africa there are archeological sites of Brombos cave and caves of the Klasies River. Bone tools were found to process leather goods. For the decoration of the body, they used a red paint or carved a geometric pattern using bone tools. They also used fire on a small fire pit, and hunted various animals and fish. They lived near the sea and can prosper by use of sea food, especially shellfish as a revolutionary food. In the hunting and harvesting society, shellfish is easy to collect and provided high quality protein to mankind. Perhaps women's contribution has been enhanced to food security.
It is unclear which is the hometown of modern people, Ethiopia or South Africa. Both are possible, but there may be another possibility.
Africa suffered from droughts from 135,000 to 90,000 years ago. Human being experienced a severe bottleneck. Probably it decreased to about 2000 people. From the analysis of genomic DNA, it was then expected that as many as 40 populations were scattered on the African continent. 74,000 years ago, the Toba eruption in Sumatra make human being experience a bottleneck again, and about 60,000 years ago, two small groups began great migration.
In the group hunting for a group of large mammals, it was necessary to consult in advance about how to catch prey and the target animal to catch. Hunting for large animals is dangerous, but fruits are so great. It can provide much food to live for a long period of time for a group of human beings. It can provide fur to surpass the cold and a lot of hard bones that are easy to process. The co-conspiracy is thought to develop their logical form of the language. Words or abstract gestures like words were used, sometimes pictures and figures are drawn on the ground. The words were arranged to clarify causal relationship, to have logics, the spatial position and time.
For the ability to speak a language, various factors are involved. The function to understand and produce languages is thought to be Broca's area or Wernicke's area, respectively, of the cerebral cortex. Both areas were born in the Hominina. The nervous system related to motor control of vocalization has changed markedly in the course of human evolution.
Anatomically speaking, vocalization involves the jaw, tongue, laryngeal organ, and head muscles. It is the muscles that control the vocal organs. They move in cooperation to create various phonemes. The rich vocalization of human beings should have developed the set of muscles of the head and the nervous system governing it. The area that controls head muscles is next to the area that controls the hand in the cerebral cortex. Possibly, the two regions might have developed in relation to each other.
In mammals, control of movement of the jaw, tongue, and laryngeal organ is performed by the premotor reticular formation. Cerebral cortex directs the premotor reticular formation. That is, the cerebral cortex controls the vocalization indirectly. The nerve extends from the premotor reticular formation to the trigeminal nucleus, the sublingual nucleus, and the pseudo nucleus. Each nucleus controls muscle movement of jaw, tongue and laryngeal organs. That is, control is near the periphery.
In nonhuman primates, the cerebral cortex for vocalization directly dominates the trigeminal nucleus and the sublingual nucleus. Direct control of the cerebral cortex also extends to the movement of hands and fingers. That is, motion commands in the cerebrum are reflected directly in the motion of the fingers.
Direct control of the cerebral cortex has developed further in humans, and the respiratory system and visceral motor nucleus are also under its control. Vocalization involves the jaw, tongue, laryngeal organ, and all breathing exercise. By controlling these movements directly by the cerebral cortex, we made possible complicated and agile vocalization. This means we can learn the control.
FoxP2 was reported in 2001 as an essential gene for the ability of conversation. It was found as a mutated gene in a family with a defect in conversation. FoxP2 is a transcription factor. The person with FoxP2 gene deficiency cannot understand such as the regularity of the sequence of the sounds in the conversation, the information of the context or the relationship with the action.
Mice lacking this gene cannot produce crying of ultrasound to attract opposite sex. Sonar of the bat is related to the function of this gene. Inhibition of this gene in Zebra finch decreased their learning ability of the song and their stability of the song. Apes also have one change in nucleotide sequence that occurred five million years ago.
It took a long time before the language system was born. First of all, we distinguished things by giving an individual name, such as to fruits, small animals, and fish. Next, words were born to indicate the location, time, how to eat, differences from similar poisoned items. Then, taking the tool as an example, the meaning as a material of the tool, its strength, its weight, ease of processing, how to use it, and more, effective usage. Words were refined during communicating among generations, and were arranged as a language. The brain already had enough capacity to store the much information. Individuals with excellent linguistic ability were also advantageous in terms of evolution. I believe that this selection is still continuing.
200,000 - 60,000 years ago: Modern human was born in Africa 200,000 years ago, and reached Eurasia after a period of time. The dairy life of modern human beings was a little better than other human beings during from 200,000 to 50,000 years ago, judging from the tools such as stone tools. The ancestry of humankind actively started to move to the Middle East about 85,000 years ago, and spread to all over the world.
It is calculated that the size of gene pool would be 5,000 of the modern human being at the beginning in 200,000 years ago. The human race seems to have advanced from Africa to the Middle East 125,000 - 90,000 years ago in the final interglacial period (Riss-Wurm interglacial period). It is estimated that the gene pool when entering the Eurasia continent is about 500,000 people in 70,000 years ago.
Ancient genomes studied in Africa can be divided into three lineages. North Africa, South Africa, and East Central Africa. What is strange is the temporal distance between lineages. It is estimated that Asians and Europeans diverged between 80,000 and 50,000 years ago, but using the same method, the three groups on the African continent were separated by 200,000 years.
Blombos Cave in South Africa was inhabited by modern humans from 100,000 to 72,000 years ago. Decorations made from shells and bones have been discovered, as well as crayons filled with Ocher inside conch shells. A 73,000-year-old stone the size of a palm was discovered that is believed to have been written with this crayon. Is it a pattern or a symbol like a letter? It symbolizes the budding of human intelligence.
It is thought that the spread from Africa to Asia occurred several times starting 200,000 years ago (First Exit of Africa), but the most successful one was between 60,000 and 50,000 years ago (Second Exit of Africa).
There is currently no evidence that early modern humans, who followed the first route north of Africa, ever arrived in East Asia. Along the southern route, remains of modern humans dating back 40,000 to 70,000 years ago have been discovered in Southeast Asia, Indonesia, the Philippines, and southern China, including the Majedbede site in Australia (65,000 years ago).
The Toba volcano on Sumatra Island erupted about 74,000 years ago. It temporarily lowered the temperature of the Earth so that mankind faced to be endangered. In particular, since the continent of India was covered with thick volcanic ash, mankind should have been near extinct if arrived.
Modern people advanced into cold weather by devising a hooded clothe with cold weather-proof. In the glacial period, Siberia was not covered with forest (Taiga) but grassland. Large mammals such as mammoth lived. The hunting prey was large, enough food was obtained by one hunting, and the cold climate was suitable for preserving raw meat and other foods. There are two subspecies in the lice parasitizing and sucking blood: the head lice in the head and the body lice in the clothes. It is thought that the body lice have diverged from head lice, since human began to wear clothes. As a result of comparing the genes of both lice, the branch was calculated to be about 72,000 years ago.
70,000-50,000 years ago: The first African group reached Australia. Humans interbred with Neanderthals in the Middle East and Europe, and with Denisovans in Southeast Asia and Central Asia.
When humans left Africa, they first came into conflict with Neanderthals in the Middle East. It is estimated that during the last glacial period (Urum Ice Age), there was a huge continuous desert extending from the Arabian Peninsula, the Middle East, Iran, and Central Asia. Furthermore, the desert was connected to the tundra desert of Northeast Asia. The spread of human being took a route around the edge of this desert. Human expansion was forced out of the remaining green areas around Ethiopia. In addition, there were various routes of expansion, including via the Sinai Peninsula and the Arabian Peninsula, and they probably moved north along the coast. During the Ice Age, the Red Sea was a sea dotted with small islands.
Our ancestor arrived approximately 66,000 years ago at India around the Arabian Sea, which was relatively greening. Analysis of genetic variations on 132 individuals from 25 different groups of Indians revealed that two genetically different ancient populations are the ancestors of the current Indians. One of them, the group named Ancestral North Indian, is genetically related to Middle Easterners, Central Asians, and Europeans. The other line, the Ancestral South Indian, has no population close to the Indian subcontinent. Negrito ethnic minorities living in the Andaman archipelago were isolated from the south Indian population in ancient times.
The route was to go to Southeast Asia. Although it was the glacier period, a horizontal movement near the equator did not take long time to advance. In the Wurm glacial period, the sea level declined, Sumatra, Java, Kalimantan (Borneo) islands connected with the Malay Peninsula, the surrounding continental shelves also landed, collectively, formed the Sunda continent. The Sunda continent was adjacent to the Sahul continent composed of Australia and Papua Island and its surrounding continental shelf. There were narrow straits between the two continents. Modern human expanded by tracing the seaside, which provided similar natural environment. Provably, this spread was rapid due to applying the hunting and sampling technique once established at the beach.
They arrived in Australia about 60,000 years ago. The Aborigines, the indigenous people of Australia, have dark skin and seem to have inherited the characteristics of the African population. At that time, Australia was connected to Papua New Guinea due to the ice age and low sea levels. The island of Tasmania is also connected and is called the Sahul continent. Wombats the size of rhinoceroses, giant hedgehogs and carnivorous kangaroos were howling. Over the course of 6,000 years, Aboriginal people expanded their range from the Kimberley region near the equator to Tasmania in the south.
50,000-30,000 years ago: Humans from 50,000 years ago left behind technology that is still relevant today. The climate is the Ulm Ice Age. Humans, who lived primarily as gatherers and hunters, developed a variety of tools and adapted to diverse environments.
As shown by figures and decorations at the ruins of South Africa fifty thousand years ago, human being has clearly an ingenuity since this time. At the latest at 25,000 years ago, human beings have expressed and presented various relationships between individuals, or individuals and groups, by art expressed in tools. The needles and threads invented 30,000 years ago helped lives in cold circumstance. They made a rope from threads. A bow has been invented 20,000 years ago.
The oldest painting of mankind was found in a cave on the island of Slavesi, Indonesia. It is a picture of a pig, a small buffalo, and Anoa, estimated to have been painted 40,000 years ago, when humans arrived in Indonesia. The first European cave paintings discovered were 14,000-21,000 years old. 40,000 years ago. In addition to animals, the painting depicts a half-beast man with protruding a nose and a tail, and there was also a figure hunting anoa. It is presumed that human beings at that time had myths and metaphors of the supernatural.
Modern humans arrived in Europe 45,000 years ago. A group with the characteristic Gravette culture was formed in Eastern Europe between 45,000 and 37,000 years ago. After that, the genome of humans after the Last Glacial Maximum differed from that of ancient Europeans. It is thought that a population change occurred between 19,000 and 14,000 years ago. A people with the Madeleine culture, who were hunter-gatherers, was established on the Iberian Peninsula. There were hunter-gatherer groups in western and central Europe.
In Europe, the latitude is high and the amount of ultraviolet rays is reduced, so dark skin cannot produce vitamin D. Vitamin D is essential for calcium metabolism, and a deficiency causes skeletal abnormalities (rickets). In order to advance into Europe, it was necessary to become white. Whitening occurred twice, first in Neanderthals and then in modern humans.
It is estimated that modern humans arrived in East Asia 40,000 years ago. However, it is estimated that the population changed after that by 14,000 years ago. Ancient East Asians are closely related to modern Native Americans and have similar genomes to ancient Siberians. The East Asians of the new era lived by hunting and gathering, and are considered to be the direct ancestors of modern East Asians. Distinctive stone tools and pottery can be found from 12,000 years ago.
The African tribes of the second exodus made distinctive stone tools, which are easy to infer from archaeological evidence. Ruins dating back 40,000 years have been discovered in Malaysia, Australia, and southern China. Human fossils appear to have been interbreeding between modern humans, Neanderthals, and Denisovans, and their morphological characteristics vary widely. Additionally, there are many deep mountain basins in the Indochina Peninsula and southern China, making it easy for human groups to become isolated, which may have led to unique development.
Mutation of the microcephalin gene (MCPH1) involved in frontal lobe development dominated 37,000 years ago (between 14,000 and 60,000 years ago). It probably affected human culture afterwards, especially language formation. Mutation occurred somewhere from Africa to India because this mutation is not detected in human beings in the south of the Sahara. In fact, there are 1800 genes that have recently been mutated. Mutations in these genes are thought to have been naturally selected with the civilization of humankind.
30,000-20,000 years ago: Humans moved north along the coast from the Sunda continent and reached the Sea of Okhotsk. Meanwhile, another race moved from Central Asia to Siberia then reached the Sea of Okhotsk. The two streams intermingled as they headed for the Americas, mainly along the northern side of the Pacific Ocean. It was the coldest era in the Ice Age, so the Bering Strait was turning into land.
There are not many measurable points showing the sea level of the mid Wurm glaciation period, but 35,000 years ago, the sea level seems to be 60-80 m lower than the present. A sharp drop about 40 m in sea level occurred around 31,000 years ago. In other words, rapid development of glaciers occurred in the northern hemisphere. It is estimated that 26,500 - 19,000 years ago the sea level decreased by about 125-135 m from now. Over the next 10,000 years, the glacier developed and the sea level remained much lower. The sea level declined rapidly by 20 m from 22,000 years ago in 500 years. Rapid warming started 19,000 years ago and the glacier melted. It became the interglacial period.
The prosperous group on the Sunda continent formed a race as Mongoloid. The body features of Mongoloid are like Neoteny (short arms, legs and a relatively large head) and pale skin color. Yellow skin Mongoloid is considered to have expanded northerly in the final glacial period and mixed with a group migrating from Siberia to the East. Genes that have lost the skin color of Mongoloid have not been identified yet. Mongoloid has moved from Southeast Asia into South China and India.
There were human race groups emigrating northward from the Sunda Continent. They went north along the arcuate archipelago located near the coast of China and the Philippines. Utilizing ocean current, they moved along the arcuate island from South China Sea northward, then arrived in Japan. Human beings migrated from the coast to inland areas along the river basin of the Mekong River, Yangtze River, or Yellow River. Since these large rivers are flowing from the Tibetan Plateau, human being had lived in the Tibetan Plateau early age. They could move to Alaska along the arcuate archipelago, but there is no evidence. It should have been mixed with a group from Siberia to East Asia.
It is thought that humans arrived in the Sea of Okhotsk from Siberia quite early. However, to reach the Americas, they had to wait for the arrival of Sundan descendants who had advanced navigational technology. Because the nature of the Sunda continent and southern China is highly productive, humans settled in these regions and were slow to move north.
There are three routes of immigration to Japan. 38,000 years ago from the Korean Peninsula to Kitakyushu, 35,000 years ago from Taiwan to Okinawa, and 25,000 years ago from Sakhalin to Hokkaido.
As humans expanded their living area, large herbivorous mammals became extinct. This is particularly noticeable in the Americas and Australia, where about 80% of species found in fossils are extinct. The remaining elephants in South Asia and sub-Saharan Africa have survived the tragedies of their mammoth and mastodon cousins. Since elephants and other large grassland herbivores survive in Africa, it is thought that the human hunters moved to Asia. They had a skill of hunting in group. Humans finally reached to Australia and the Americas had advanced hunting techniques, so they hunted efficiently and may have driven large animals to extinction.
There were evidences that 23,000 years ago human being collected grain seeds. Because of ruins using a furnace by old human being, they are considered to be a semi-settlement life. Also, evidence of baking bread was found from the furnace 14,000 years ago. In order to make bread, techniques are needed such as threshing and grinding grains.
20,000 - 15,000 years ago (1): The Earth entered a period of great freezing. North America, Siberia, Europe were covered with glaciers. The sea level decreased by 150 m from now, and the continental shelf expanded. The climate has reversed in 19,000 years ago and the rapid warming started.
It wasn't always cold during the Ice Age. The isotopic ratio of oxygen stored in the Greenland ice sheet suggests that there had been occasional warm periods. On average, temperatures were low. However, the changes in climate were much larger than during the interglacial periods. In other words, during the Ice Age, the climate changed rapidly. This means that stable agricultural production was impossible. Humans had no choice but to continue their hunting and gathering lifestyle, making use of vegetation that was changing with the climate. This ultimately led to the spread of humans across the globe.
The origin of agriculture is unknown. Traces of the early days of agriculture can be found on the current continental shelf, and it is believed that they were all submerged under water. However, it would not be surprising if agricultural techniques spread even in the middle reaches of major rivers, areas that were not submerged. According to ice core data from Greenland, during the Ice Age there were large fluctuations in temperature, humidity, and dryness over a period of several years. Even if they planted a field, they could not expect a harvest that year. Therefore, people lived on the move in search of food that was easily available at the time. After entering the interglacial period, there was almost no fluctuation in temperature, which made it possible to start farming.
Evidences of art have been discovered in Europe for about 50,000 years ago, but especially at these time, human being elaborated fine cave paintings. Lascaux is drawn at 15,000 years ago, Altamira is a ruin of 18,000-10,000 years ago. The origin of the Great Eurasian language family proposed by Dr. Greenberg dates back 15,000 years ago. The Indo-European language family, a big branch, is said to have been established 8,000 years ago.
In the Wurm glacial period, it was coldest about 19,000 years ago. Temperature was 6 degrees lower at the average than now. The ice sheet went the most south and the land above 50 degrees north (North America, Canada, the Scandinavian Peninsula, Siberia) is covered with ice sheets and Greenland and North America were connected by ice sheets. There are large rivers flowing into the Arctic Ocean in Siberia now, but they were stopped by the ice sheet and a huge glacial lake appeared. Europe was covered with glaciers to England and the Baltic Sea.
The volume of the ice sheet is estimated to be three times the current ice sheet in Antarctica and Greenland. As the water was on land as ice, the sea level declined. It is estimated that when the glacier was the largest it was 150 m lower than the current sea level.
Inland parts dried. Of the land between 30 degrees both North and South latitude, the area of the desert is about 10% now, but before 19,000 years ago, it reached 50%. In particular, they were distributed in two belt-like shapes centered around both 20 degree North and South latitude, and sand dunes developed in North Africa, South Africa and Australia. For this reason, the human race remaining in Africa is divided into three groups in the north, the south and the equator, there is a possibility that the genetic difference became larger among them.
The yellow sand has been brought from the desert inland China. Examining the yellow sand, in addition to deserts distributed in mid-latitudes such as Takla Makan and Gobi, it also flew from the northern Asian continent such as northeastern China, Mongolia, Siberia widely from about 75,000 to 10,000 years ago. It is thought that the desert had spread in the central Asian continent of the last glacial period.
20,000-15,000 years ago (2): There is a vast continental shelf on the sea side of the area where an ancient civilization appeared. The history of ancient civilization before its birth may have been developed on the submerged continental shelf. In addition, ancient civilization appeared around 30 degrees north latitude, where crustal movements are severe due to continental collisions.
It is thought that the continental shelf was coastal plain during the ice ages. The average depth of the continental shelf is approximately 130 m and the width is 78 km on average. It reaches about 10% of the ocean area. This land was given to our ancestors in exchange for the ice sheet and the desert. From the distribution of continental shelf, we can infer the distribution of human beings 19,000 years ago.
First, Persian Gulf. The Tigris / Euphrates's large river would have been one and would have given moisture to the valley of the Persian Gulf. Human beings left for Central Asia from here. The shelves of off Bombay in India and Bengal Bay provided pretty large plains.
The Red Sea and the Mediterranean Sea became inland Sea. The Mediterranean was divided into two by the Italian Peninsula, and the Aegean Sea became a plain where the island and the lakes entwined. The human race in Europe ran down south of the Mediterranean coast according to the expansion of the ice sheet. The vicinity of the UK became a vast plain. The Baltic Sea became a frozen, wide valley. The European plains were high in latitude and cold, so population density was low. The water overflowing from the lake of Siberia flew as rivers from the Caspian Sea to the Black Sea, on the other hand, also poured into the Baltic Sea (valley at that times).
Many human beings lived in the Sunda and Sahl continents, centered in Southeast Asia. In East Asia, there was a large continental shelf now called the East China Sea. It was a relatively temperate even during the ice ages. Also, as a result of the distribution of many islands, the human race might have developed greatly here. The Sahl continent was so closer to the Solomon Islands (which was one island) that human being could go by ship.
Northward from the Sunda continent, there was a land from the Philippines through Taiwan, so the South China Sea may have been inland sea or a lake. The East China Sea became land, where Yellow River and Yangtze River gave moisture. Were the two big rivers joining one? Their estuaries will be around Okinawa. The northeast area where human beings could live might be Hokkaido. In Okinawa, the oldest human bones were found in 2007, estimated to be 20,000 years ago. In the case of the Japanese archipelago, global warming preceded about 3,000 years because there were no huge ice sheets like in Europe and North America. Earthenware was invented in this area at around those era
The Sakhalin connected to the Siberia. The Kuril Islands divided the Okhotsk Sea from the Pacific Ocean. The Aleutian Islands surrounded the Bering Sea with the Bering Cross Bridge. This area is called Beringia. Beringia is the third largest in the submerged continent.
The Gulf of Mexico and the Caribbean Sea became the inland Sea, but the human race would have not yet reached.
15,000 - 10,000 years ago: The Earth became warm and glaciers melted. Especially the destruction of a huge glacial lake caused the sea level to rise all at once, so human beings had to move to inland from the coastal plain. As heavy thicker glaciers pushed the crust down, Scandinavian peninsula and Canada are still rising now.
Glacier melted gradually due to global warming. As the continent was tilted towards the Arctic Ocean, water was caught by glaciers to form a huge lake. The glacial lake broke down and a large amount of pure water flowed into the vicinity of the Arctic Ocean. This caused oceanic floods. It is estimated that the oceanic flood happened 3 times (about 14,000 years ago in the first time, about 12,000 years ago in the second time, 8,000 years ago in the third time). Sea level rose rapidly about 10 m by one marine flood. The flood hit the coastal plain. This 10 m rise of sea level at a time was enough to destroy the human culture which had spread to the beach.
Among the three, the most famous one is the marine flood of the Younger Dryas cooling of 12,000 years ago. The lake of Siberia reached the Arctic Ocean, and a lake of North America flowed out, the Arctic Ocean and the North Atlantic Ocean were considerably desalinated. As a result, the deep-sea circulation stopped that sea water had been submerged from the North Atlantic into the deep sea. The warm Gulf of Mexico Current ceased, which had been flowing northward in the Atlantic Ocean. Temporary cold season hit Europe and North America. During the cold season, human being developed agriculture in the Middle East and Mesopotamia region. The population 12,000 years ago when agriculture began was about 5 million.
During the cold season, humans developed agriculture in the Mesopotamia and the Middle East. As the ice sheet receded, forests expanded again and deserts shrank. In Levant region, wild wheat, rye and barley were overgrowing, and a group called the Natufs established the first settled society. After the last ice age (12,000 years ago), a large-scale migration of farmers originating from West Eurasian groups occurred, and they expanded while interbreeding with earlier hunter-gatherers. This resulted in the formation of early European agrarian groups. This migration also extended to Ethiopia.
Here are my guesses of the main areas that were submerged and the new destinations of human beings living there.
People who lived in the Mediterranean East Coast Plain went back along the Nile River and founded the Egyptian civilization. Other of them moved to the Aegean Sea, Anatolia. People who lived in the coastal plain of the Persian Gulf migrated to Iraq along Tigris and Euphrates River, and built a Mesopotamian civilization. In the Middle
People who lived in the coastal plain of the west of the Indian continent migrated along the Indus River and built the Indus civilization. People who lived in Sunda moved diversely as the sea level rose. West to Indochina peninsula, East to Polynesia, North to China, Japan and Korea. People who lived in the coastal plain of the East China Sea migrated northward along the Yellow River and the Yangtze River. The first cereal (rice) cultivation was made about 15,000 years ago is the Yangtze civilization.
Families who moved to Siberia lived in south region of the glacier. The candidates are in the coast of the Japan Sea and the Okhotsk Sea, where had become inland sea. Also, Mongoloid adapted to the cold climate had lived in the southern side of a huge glacial lake. Along with global warming, glacier lake moved to the north, and they may have moved north along with the lakes. After the glacial lake broke down and disappeared, they may have moved to the Americas across the Bering crossover. The Bering crossover was accessible from 14,000 years ago to 11,000 years ago. When the Bering Strait landed, the Kuroshio current should have flowed towards the North American continent in a substantially horizontal direction. There are records that Japanese fishermen in the Edo era were flowed to the Aleutian archipelago. In the past, some of the people can get in the ocean current and can migrate from Aleutian Islands to North America.
The first culture in the Americas is Clovis culture which makes spears with characteristic stoneware around 11,500 years ago. When they first appeared in the Midwestern part of North America, they spread quickly throughout the North American continent and then expanded to Tierra del Fuego at the southernmost point in South America only in 1000 years.
Around this time, Jomon pottery was made in Japan (bean grain pottery found in Senpukuji Cave, Setogoe-cho, Sasebo City (12,000 years ago)). With the addition of earthenware, the meal changed completely. Until then, raw vegetable and meat were barbecued on stones. The staple food has been replaced by preservable starch-based foods such as walnuts, chestnuts, acorns, and grains. Animal meat became rare, with the addition of fish and shellfish. The distribution of various precious stones in the Jomon period was about 200 km from the production area. This distance was within the scope of logistics, politics, mutual understanding, etc.
Dogs were domesticated in East Asia 15,000 years ago. Dogs are rare animals that have a strong sense of belonging to a group and can grasp human facial expressions. It was useful as a watchman in the hunting life.
10,000 - 8,000 years ago: The Earth warmed rapidly and the sea level rose. Agricultural technology was discovered all over the world. Human beings have developed agriculture and spread to various places along with the language.
Agriculture is said to have started in a fertile triangle 10,000 years ago, but occurred around the world almost at the same time. It is estimated ten independent areas that agriculture started in the world. In China, rice farming started 8,000 years ago. There are ruins of rice field, where people pulled water and irrigated. Pumpkin was cultivated in the America continent 10,000 years ago, corn was 9,000 - 8,000 years ago, peanuts 8,500 years ago. In New Guinea, agriculture of banana, taro and yam potato started 7,000 years ago. As the temperate climate had continued, the people who settled and began agriculture became relatively rich.
There are 200,000 kinds of angiosperms that makes flowers bloom and seeds, but there are only thousands of edible plants. Among them, there are hundreds of things economically possible for cultivation. Currently, only 80% of agricultural crops consumed in the world in one year are a dozen or two cereals, beans, root vegetables, vegetables, and fruits. These main plants have been cultivated for thousands of years. Only five major species are domesticated in mammals, such as sheep, goats, cows, pigs, and horses. Others are camels, donkeys, alpacas and buffaloes, but the environment is limited where they can be bred and be functional for production.
Livestock seems to have established at about the same time as the establishment of agriculture. Livestock has the great advantage that meat can be obtained without hunting. Since 10,000 years ago, sheep have been domesticated in the Taurus Mountains and goats in the Zagros Mountains in Levant. At the same time, cattle were domesticated from the wild Aurochs in the Near East and India. Pigs were 10,000-9000 years ago in Asia and Europe. Chickens were in South Asia 8000 years ago. 8000 years ago, Mongolian horses were domesticated in the central grasslands of Eurasia. Llama was 5000 years ago in the Andes in the Southern America. Turkey was 3000 years ago in Mexico.
The use of "secondary" products such as milk, hair, traction force which obtained without killing livestock were one important advance in agricultural development. Analysis of the organic residue of more than 2,200 pottery excavated from the Middle East to the Balkan Peninsula shows the first use of milk 9,000 years ago. The use of milk was particularly important in the present Northwest Turkey, and the environmental conditions in this area were considered particularly suitable for cattle. 15,000 years ago, dogs were domesticated in East Asia. According to the analysis of the genetic clock, it was estimated that the cat separated from the wild cat in the Middle East 100,000 years ago. It seems that it was domesticated by humans kept in the Middle East since 9,000 - 10,000 years ago.
Clams were cultivated in the Salish Sea in eastern Canada 9000 years ago. When the size of the fossil clams was examined, the size of the shellfish was larger than before 11,500 to 10,000 years ago. Humans, who arrived 9,000 years ago, began farming clams, and 5,000 years ago they were developing shellfish farming technology. The ledges of the shallow sea were surrounded by walls to protect the shellfish from predators such as fish and crabs, and to feed plankton and mollusk meat.
The Indo-European language family originated from the Anatolian Plateau of Turkey and began spreading about 9,000 years ago. The geographical distribution of the language, the time when farming started in that area, and the distance of closely related relation of language are correlated. The people living there are not descendants of conquerors who conveyed farming techniques and the Indo-European language. Only agricultural skills and language were conveyed. People with excellent technology introduced languages with technology, to those who learned actively the language.
Grains can be preserved for a long time, so wealth can be preserved. Agricultural culture with grain as a staple food has developed greatly. Traditional hunters kept living as they were in mountainous areas, forests, coastal areas where agriculture cannot be done.
8,000 - 6,000 years ago: The Earth was warmed towards the Hypsithermal period, and the climate became warmer globally than in the present age. A prototype of the walled city was built.
During the Hypsithermal interval, the area from North Africa, India, to East Asia became wet climate. In particular, the current Sahara desert had become extremely moist, and large vegetation had spread inside it. Sea level rose around the world 5,000 - 7,000 years ago when global warming peaked. It is thought that half of the Kanto Plain was covered by the ocean deduced from the distribution of kitchen middens (Jomon/Flandrian transgression).
As the sea level rose, a large amount of water flowed into the Black Sea through the narrow Bosporus Strait from the Mediterranean Sea. Perhaps the Black Sea coast would had been hit by a gigantic flood. In the sea bed of the Black Sea, a trace of a large amount of water flowing about 7,600 years ago, that is, canyons were discovered. The Great Flood of Noah, the Great Flood of Gilgamesh epic poems may have been handed down a major incident at this time. In addition, the shallow Bosporus Strait may have been made over land bridges several times due to climate change. Moses' miracle of breaking the ocean may have actually happened. Similar incidents would have taken place all over the world.
The oldest ruin of the walled city was Jericho of Jordan 8,000 years ago. Rectangular buildings using sun-dried bricks were preferred. Storage facilities and bread kilns were also provided. Buildings are interpreted to be used for defense or religious facilities. There are also large-scale residences in the vicinity 11,000 years ago. People have lived in Jericho since ancient times and have built a rich culture that makes cities.
In the ancient Orient, the use of earthenware was from relatively old, about 7,000 years ago. Earthenware was first made with sunburn, after that it became to strengthen by adding heat. Heat of 700 ~ 800 C is necessary to make earthenware. This level of heat was achievable by making a large bonfire or using a furnace.
Mutation of the ASPM gene determining the number of neurons in the cerebral cortex is estimated to have occurred about 6,000 years ago. The ASPM gene was identified as a causative gene of a genetic disease that became encephalopathy with a recessive mutation. As ASPM mutation coincides with the time of character or city formation, is it a genetic cause of urbanization ability?
Eyes of European people are blue (blonde hair, white skin), which is derived from mutation of HERC gene 6,000 - 10,000 years ago. From the analysis of genes it was thought that a group with a blue eye gene migrated from the shores of Black Sea to Europe. The HERC gene controls the neighboring OCA2 gene (expressed in black pigment cells, which seems to be involved in the biosynthesis or intracellular transport of melanin). Is the blue eyes spread among Europeans due to gender selection?
Most Africans and Asians have an old type (111 A) of SLC24A5 genes involved in skin color. The new type of gene (111 T) differs by 1 amino acid, 99% of the Caucasian has it. It is estimated that this change became dominant among Caucasians 5,000 - 12,000 years ago.
Several city names (including Ur of Caldea) were found among the letters written on Sumerian clay board known as the oldest letter, but most of them were not Sumeric. On the other hand, it was written in an unknown language, not the language of other Semitic people that had hostile relations. This suggests that the Sumerians were not from this area from the beginning but people who emigrated from other places and borrowed words from unknown people who originally lived in Mesopotamia.
The ancient English who made Stonehenge is believed to have been hunting-gathering life 6000 years ago. The origin of the people who lived in Britain during the Neolithic Age are regarded as Anatolia (modern Turkey).
Since 8,000 years ago, Mesoamerica began cultivating life changed from hunting-gathering life. Maize is a typical example. Making pottery and weaving cloth started independently.
6,000 - 5,000 years ago: The hypsithermal period ended, then the interior of the continent dried. Nomadic people gathered around the large rivers. Around the area, farming and nomadic culture fused. The development of agriculture and livestock farming had made human living stable and affordable. The population had increased more than ever, the settlement developed into a large village, a city state emerged.
Mesopotamia was located downstream of the Tigris / Euphrates rivers, where was a very suitable area for agriculture at that time. The oldest ruins are of the Sumerians. Flood control and irrigation were done in 6,200 years ago. Agriculture was the main industry. Although the village was scattered, several city states were established 5,500 years ago. Sumerian city states fought each other over a farmland. One of them is the land of Eden. The nomadic people of this time had great military power, sometimes they seemed to invade the agricultural tribe and the forest people.
5,500 years ago, in the Sumerian city-state, clay pieces called tokens, engraved with the prototype of letters, were used as a record of trade. This is the prototype of both money and sphenogram.
The oldest library in the world in ancient Babylonia was built about 5,000 years ago and contained a large number of clay tablets engraved with sphenogram. In addition, the number of clay tablet documents found in the Sumerian ruins was about 300,000, 95% of which were records of the national economy. Bills, receipts, sales contracts, adoption and contractual consents, testaments, worker and salary lists, letters. The rest are votive texts of goods and buildings, accounts of temple property (mainly grain), educational documents, religious documents on spells, and literary works. Literary works are myths and epics, including lyric poems (threnody, hymns) and didactic poems (proverbs, wisdom literature).
The oldest copper product was made 6,000 years ago on the Anatolian Plateau in Turkey. Bronze was first made in Anatolia and Mesopotamia 6,000 years ago. Copper was relatively easy to obtain, but tin was not found in the both regions and was found nearby near the German-Czech border or in the Britain. It is said that the Phoenicians transported the tin. Bronze, which is harder than copper, spread to Egypt, China and Indus.
Downstream of the Nile River was also a fertile land. The Nile River regularly flooded every year, and flood control project created the history of Egypt. Because Egypt was surrounded with deserts and a relatively isolated area, the development of the Kingdom occurred first in the world. The flood control project of the Nile River required enormous labor and large-scale collaboration, so a strong leadership was born. By around 6,000 years ago, 22, 20 Nomos (small tribal state, city state) were formed, respectively in the upper and the lower Egypt. Eventually they gathered up in the upper and lower Egypt. Finally, 5,000 years ago, the first dynasty was unified by the legendary King Menes, first Pharaoh of Egypt. Hieroglyphs were used in Egypt.
Varna civilization was established on the west coast of Black Sea 6,000 years ago. Gold products are featured. Horseback races with Kurgan culture spread old Indo-European family of language in Europe and the Middle East. Beakers formed their own culture on the Iberian Peninsula 5,000 years ago, emigrated to Central Europe and spread their culture. The original Beaker people was from a nomad who lived in the meadow area spreading from Ukraine to Kazakhstan.
The oldest rampart of China is the castle wall of Chengtoushan. It was a city surrounded by a 360 meters diameter circular wall built in 6,400 - 6,200 years ago and has a castle gate in north, east and south. The altar was built and rituals wishing for the rich rice farming were held there. Yangtze civilization is a civilization based on a rice farming and fishery, it was an ancient civilization heterogeneous to so-called the four great civilizations based on upland dry field and pastoral type.
5,000 - 4,000 years ago: As agriculture became popular, civilization developed dramatically. Demand for fire increased due to brick making for city construction, earthenware making, smelting metal, and growing population. In the plain, forest trees were cut down and used as firepower. At the same time, the destruction of the environment began that turns the forest into agricultural land.
There is a mystery that there is no evidence that people lived in ancient Southeast Asia from 6,000 to 4,000 years ago. About 5,000 years ago, Southeast Asia was hit by a drought that lasted for 1,000 years. Examination of the annual rings of the stalagmites in the Tham Doun Mai cave in northern Laos found evidence of a drastic decrease in precipitation 5,100-3,500 years ago. During this period, the green Sahara turned into desert, the Akkadian Empire collapsed, and the city of the Indus Civilization was abandoned. In addition, in a climate simulation of the time when Sahara turned into desert, not only the monsoon in Southeast Asia would have disappeared, but also the El Nino phenomenon would have been prolonged in the Pacific Ocean, and floods would have occurred frequently in East Asia. In China, Yu the Great, who ruled the flood, built the first dynasty, Xia.
The northern part of Mesopotamia is called the Assyrian region, and the southern part is called the Babylonian region. The Babylonian region is further divided into the Akkad region in the north and the Sumer region in the south. In the middle region of Mesopotamia, Akkadian started to live, who were a nomadic branch of Semite peoples. They accumulated power while learning the culture of the Sumerian people. Finally, the Akkadian conquered the area of the Sumerians in the south and founded the Akkadian dynasty 4,200 years ago. King Sargon was able to conquer the Sumerian due to their out-standing army which had a swift mobility with the bow and arrow as the main weapon. King Sargon of Akkadian unified the tribes of different languages, so he decided to use Akkadian as a common language. He also made a zoo. Since Sargon ruled humans, he might have thought to control animals next time. Naram-Sin, the fourth King of the Akkadian Empire, declared himself a god first in history. The Akkadian dynasty declined in 200 years. In the political confusion, the Sumerians recovered their forces again, the Ur 3rd dynasty was formed. King Ur-Nammu, the founder of this dynasty, is known as the publisher of the world's oldest law (Ur-Nammu Code) prior to the Hammurabi Code.
In Egypt, the pyramid was built during the Old Kingdom era (5,000 - 4,100 years ago). Especially the huge pyramid was made in Old Egyptian Kingdom 3rd-6th Dynasty era (4,600 - 4,200 years ago). The Three Great pyramids and Sphinx are very famous of the 4th Dynasty, located in the suburbs of Cairo, of the King Khufu (the largest pyramid), Khafre and Menkaure.
The Crete civilization was established in the Aegean Sea in the eastern Mediterranean. People who came across the sea from the advanced regions such as Egypt, Anatolia, Syria and Lebanon and others actively worked around Crete. About 4,600 years ago the Bronze Age began in the island. Agriculture was done such as wheat and olive, livestock farming such as sheep and goats. In addition, maritime trade has developed, and the Cretan is regarded as the oldest maritime commerce navigator in the world.
4,500 years ago, Beakers moved from Europe to the UK, and almost began to occupy the population of Britons, to 90%.
In the Indus river basin, ruins are found such as the planned cities Mohenjo-Daro and Harappa. These cities were constructed 4,500 to 3,800 years ago. Indus civilization is a bronze civilization, irrigation agriculture and livestock farming were the main means of production. Indus characters and stamps are left. They had traded with the Nations in Mesopotamian region. Hypothesis has arisen that one of Mesopotamia's Nations made the cities for trade or the colonies because it looks like as if high-level of civilization would suddenly appear.
The situation of China in this era is currently being constructed. In the Yellow River Civilization such Yangshao and Longshan culture, villages were formed depending on farming and hunting. Coloring earthenware is characterized by Yangshao culture, and black pottery baked at high temperature is in Longshan culture. As the heyday of Yangtze civilization, where rice cultivation was main industry, there are Qujialing culture and Liangzhu culture. Many tools made of gemstone were excavated, and trade with Yellow River civilization was also demonstrated. Although the age has not been confirmed, the Sanseitai ruin of Sichuan Province was established around this time and had its own culture.
There is reliable evidence that production of Chinese silk dates back to 4,570 years ago. The old silk found in the city of the Indus civilization is considered to be 4,450 to 4,000 years ago. For production of silk, oak silkmoth was used in India and silkworm was in China.
4,000 - 3,500 years ago: The kingdoms were established in various places, and built city civilizations. The letters were invented in ancient Babylonia, Egypt, China, Maya civilization. By using letters, society was recorded, organized, authorized and became the foundation of the kingdom.
In Crete, large palaces were built about 4,000 years ago in Knossos, about 3,700 years ago in Faith, and in Maria. The city developed around the palace. Labyrinth of Knossos is famous. The city without a wall shows they were a bright and peaceful marine civilization. They already had characters. They made progress from early pictograms to line characters. People recorded the accounting of the palace on the clay board. Cyprus produced abundant copper which was traded by the Minoans. The eruption of Thira volcano destroyed the Minoan city 3,600-3,500 years ago.
The middle Kingdom era (4,100 - 3,600 years ago) was started by local big families living in Thebes at the middle of the Nile river. They extended the power to unify all Egypt and set the capital on Thebes. In Egypt, they further developed technology to make copper from copper ore. As a burial item of King of Egypt, many copper needles, pins and bracelets are excavated. In 3,600 years ago, the Hyksos of Semitic semi-nomads invaded into Egypt from Syria. The Hyksos overwhelmed the Egypt army with Chariots pulled by horses, conquered the Middle Kingdom. Egyptians were to be under the control of foreigners for the first time for about 100 years.
After Sumer and Akkad, it was Semitic Amul who dominated Mesopotamia. About 3,900 years ago they built Babylonian kingdom with Babylon as the capital. King Hammurabi of the sixth unified the Mesopotamian region by the war of 30 years of conquest and built a centralized nation. Hammurabi enacted the law which is the culmination of the laws of the past. The ancient Babylonian kingdom became the center of thought and civilization in West Asia. The King Hammurabi set a calendar and developed the legal system. The King declared release of people from slavery and debt, which was regarded as a deal with God. Using copper, metalware was made. The Babylonian and its sphenogram became the diplomatic language of West Asia. Their astrology, calendar, building technology, weight unit and so on affected Greece as well. The ancient Babylonian kingdom declined after King Hammurabi's death and was destroyed by Hittites 3,530 years ago.
The prosperity of the ancient Babylonian kingdom stimulated the surrounding ethnic groups. A large number of ethnic groups advanced to Mesopotamia aiming for wealth. Also, nomads in Iran and Asia Minor, Central Asia, Northern Russia's Indo - European tribe have made a big move. Hittites first moved to the Anatolian peninsula where they learned the production technology of ironware. Hittites conquered the surrounding tribe and beat the old Babylonian kingdom, but their kingdom was short-lived. The Aryans migrated to ancient Afghanistan from 4,000 years ago to 3,500 years ago. The Aryan people are divided into two, one migrating to Punjabi (Indus basin). The other moved to Iran and became Iran-Aryan. Some historians have a doubt about the existence of Aryan people.
4,500 years ago, the Phoenicia merchant had a record of carrying tin. Bronze (an alloy of copper and tin) was invented 4,000 years ago. Copper was too soft for weapons, but it became harder when turned into bronze. Furthermore, bronze was free to deform, weapons such as swords and spears developed. The technique of making bronze quickly spread all over the world. In the ancient China, sophisticated bronze wares were made in the age of the Shang (Yin) 4,000 years ago. Bronze and its accessories also functioned as money.
A city state Erlitou was born 4,000 years ago at the middle of the Yellow River, China. Erlitou is regarded as the legendary Hsia dynasty. A large amount of jewel instruments and bronze ware was excavated. About 3,500 years ago, the Han Chinese people arrived in northern China and oppressed the indigenous people of the Yangtze River Basin (originally thought to be people who lived on the continent of Sunda). The Han people established the Shang Dynasty. Ethnic groups of the Yangtze River basin spread to Japan, Southeast Asia, Polynesia. They are the people of the Altai language.
Many ancient civilizations appeared on the plate boundary. There are risks of earthquakes, volcanoes and tsunamis, but in general, they are rich in water. A moderate natural disaster may encourage people's cooperation and preparation, and may have revived the challenge spirit.
3,500 - 3,000 years ago: Nomadic people in Central Asia moved to various areas. This is the oldest record written that nomadic tribes entered into the ancient civilization area. Ethnic groups who lived near Egypt and Babylonia became civilized under the influence of ancient nations. Iron was made in Anatolia 3300 years ago, but at that time, it was lump iron. The iron was not completely melted, so it needed be reheated and beaten to make wrought iron.
The Phoenicians started to form city states 3,500 years ago. They developed shipbuilding and navigation technologies from 3,200 years ago, and conducted sea trade, and advanced from North Africa to the Iberian Peninsula. The alphabet is thought to have been invented by the Phoenicians as a convenient letter that mediates Mesopotamian Sphenogram and Egyptian hieroglyphs which are both trading partners. The prototype of the alphabet was born in the ancient Orient. The Phoenicians conveyed the excellent civilization and culture of Mesopotamia and Egypt throughout the Mediterranean, and promoted the development of ancient Greece and ancient Rome.
From 3,500 years ago for several hundred years, Dorians and Achaeans, move down to south of the Balkan Peninsula. They destroyed Mycenae and Creta civilization 3,200 years ago, and swept the eastern Mediterranean as sea people. They built many cities called Polis like Phoenicians. Later, they are called Greeks.
Egypt ran out Hyksos. Egypt came to the most prosperous era in 3,500 years ago, including strengthening militarism and conducting expeditions abroad. King Tutankhamun of Egypt 3,300 years ago is famous for its golden mask and coffin. Egypt battled with the mighty Hittite Kingdom at Kadesh, but later had a co-prosperity posture such as marriage relationship. Egypt declined gradually from 3,000 years ago and received invasion by Assyria and Persia.
The ancestors of Hebrews are people who emigrated to the present Israel from Mesopotamia around 4,000 years ago. Some groups moved to Egypt (due to famine? Hittite's mercenary? Egypt invasion?). They were treated as a slave under the New Kingdom of Egypt. About 3,200 years ago, a group led by Moses escaped from Egypt. They established Judaism and became the backbone of the later Jewish people. They built a kingdom and prospered in era of King Solomon.
Mesopotamia invaded the nomadic tribe from Central Asia, and many kingdoms such as Hittite, Mitanni, Cassito were established in parallel and were in a state of antagonism. Meanwhile, practical academic technologies advanced such as arithmetic, 60-digit method, astrology, formation of calendar, law, etc.
The Indus civilization flourished in the plains that crossed the Indus River Basin to the present Bombay, but it was destroyed about 3,800 years ago. Later, Aryan people gradually moved to the same area by clan from 3,500 years ago. As the Aryans had technology of iron usage, they could dominate the Dravidans who had a dark skin color. Creating a caste system (class system) based on their religious thought, they were in the ruling classes Brahmin and Kushatria.
In China the King Tang opened the Shang dynasty 3,500 years ago. In a history book Shiki, it is called Yin. Characteristic of politics of the Shang is theocracy, decided by divination all the national affairs such as politics, military affairs, agriculture, etc. by using the oracle bone script. The oracle bone character is a prototype of Kanji. Production activities were carried out by clan, and ancestral worship was regarded as the root of their religion. Many large bronze bowls with bizarre designs were discovered, showing that they had advanced technology to make bronze ware. The Zhou dynasty that occurred in the western part of China gained a know-how to make iron through trades with the central Asia region. 3,000 years ago, King Wu of the Zhou dynasty beat the King Chou of Shang dynasty.
In Central America, the Olmecca civilization was established about 3,200 years ago, and reached its peak in 2,500 years ago. In addition, the Sapoteca civilization was established for 2,600 years ago. They devised a Maya character, and built many monuments. They also created a long-term calendar that starts in 3,114 BC. The Maya character is a pictogram that contains pictures and symbols characterized by the profile of a human or animal in a square.
2,500 - 3,000 years ago (BC 1,000 - 500 years): The national backup is necessary for practical use of iron. Iron technology was also necessary for military power to maintain and expand the nation. Roman was founded. Hebrew was at its peak. Brahmanism and caste were established in India. In China, Zhou dynasty collapsed due to the invasion of nomadic people, and entered the spring and autumn period. Iron was spread in Europe.
It is thought that modern nomadism was established about 2,800 years ago. They were control of flocks such as castration and equestrian, technology of milking and processing. Nomads have a lot of dependence on agricultural production. Nomad industry was trade and livestock supply. They governed grassland areas where agriculture is impossible.
The Celts in Eastern Europe (Romans called them Gaul) had resided in the upper line of the Rhine, Elbe and Danube rivers. They had the power gradually to drive away the aboriginal people, and spread to almost all Europe before 2,700 years ago. The Celts were the first European representatives of ironware culture. Basque people who live in the Pyrenees might be one of the aboriginal groups that was depressed by the Celts.
It was the Scythia that made the kingdom for the first time in equestrian ethnic groups. It was confronted with the two countries of Greece and Orient, based on the northern Black Sea coast, around 2,600 years ago. They were accustomed to riding horses and were the strongest troops that could use bows and arrows while riding. The army with high mobility overwhelmed Chariot, the main force of the military of other big kingdoms of these days. The equestrian people invaded the civilization area many times in following era and became the driving force which made Empire. The ethnic group of the Varna civilization that flourished on the east coast of the Black Sea was later called Thrace, and reached its peak as a kingdom 2,600 years ago.
Each Greek police has developed from 3,000 years ago. Although economy of Athens was based on slavery, Athens invented the Republic. Democratic politics created Ionian natural philosophy (Thales: the origin of all things is water, Heraclitus: all things flow, Pythagoras: all things are numbers, Democritus: all things are made of atoms), and in Athens, Sophists (Socrates etc) were active. 2,800 years ago, the use of casted money began at Lydia. Since Greece is a land with low productivity, they developed commercial, trade and craftsmanship and built up the monetary economic zone. 2,700 years ago, Rome was founded. Rome shifted to the Republic by influence of Athens 2,500 years ago.
In Egypt and Mesopotamia of rich river basins, neighboring ethnic groups repeatedly invaded and built the kingdom. Assyria dominated Egypt, Syria, Mesopotamia, and eventually unified Orient 2,700 years ago. Assyria has powerful armies, mainly of cavalry. They built and maintained the highway. Assyria forcibly moved many ethnic groups with its militarily, and imposed heavy taxes to them. The Jewish people were one of them, and in the Old Testament, Assyria is portrayed as an ethnic who favorite blood. After about 140 years of control, Assyria declined due to the independence struggle around of each country.
In India 3,000 years ago, Aryans who acquired steelmaking technology advanced to the east area along the Ganges River. Agricultural production increased, commercial and industrial yield were developed, accordingly villages developed into cities or urban states. Mixed with indigenous people (such as Dravida), progress of differentiation of the status class, the caste system was born. Brahmanism, which is the basis of the thought of the caste system, used Veda as a scripture, and the ceremony of the religion was prepared. As society evolved, the power of Kushatria and Vaisha strengthened, who had political and military power or economic power, respectively. Some of Kushatria and Vaisia, who were suffering from the domineering of Brahmin, sought new ideas to adapt to the new era. Religious people who train in the forest and conduct training and inner thinking have emerged, and the oldest philosophy called Upanishad was born. Jainism and Buddhism were established based on Upanishad philosophy.
In the Zhou dynasty established 3,000 years ago, territory was given to the family by the king (the head family), and politics was managed by the clan feudal system. When the power of the Zhou royal family declined, it became the spring and autumn period when many kings competed against each other. In the spring and autumn period, iron making technology became popular, and productivity also increased. The kings had scaled up policy of increasing wealth and military power in each country and sought talented person. In the trend of realism, many thinkers and schools appeared, and many books were written. These are collectively called "Hundred schools of thought". It gradually changed to the Ages of the warring state 2,500 years ago.
Individuals who revolutionized the interpretation of humanity appeared at the same time around 500 BC in the world. Jaspers called this the Axial Age. Great philosophers and religions were produced in the east and the west, such as the Greek Sophist, Zarathustra in Zoroaster, Buddha, and Hundred Schools of China. They thought that slavery and human sacrifice should be denied, which were regarded as evils of ancient society, and that family values and laws should be respected. However, according to the historical database Seshat, the birth of new philosophies is scattered over a wide range of times from 1200 BC and cannot be simultaneous.
2,500 - 2,000 years ago (BC 500 - 0): The Earth warmed since 2,500 years ago, the productivity of agriculture rose. Empires such as the Roman Empire and Han Empire have stabilized and thrived. From the introduction of steelmaking technology, society became stratified in 1,000 years, and people were separated to aristocrats and slaves. A philosophy was born from the affluent life of aristocrats.
After the Assyrian Empire was destroyed, the Neo-Babylonian Empire was one of the countries where independence had recovered. The reigns of the two Kings Nebuchadnezzar are famous. Since the Neo-Babylonian Empire captured the Jews as slavery, the capital Babylon has a poor reputation as a evil religion or a depraved city in the Old Testament. Two kings built magnificent Jigrads and aerial gardens. The Jigrad is regarded as a model of the Tower of Babel. Achaemenid dynasty of Persia was the next empire that has expanded its power. 2,500 years ago, when Darius I established the empire ranging from northern Greece, Turkey, Egypt, Middle East, Mesopotamia, to Iran. Departing from one of races of the Media kingdoms, he did his feat in just 50 years. Although Assyria did tyranny politics, Darius I was tolerant of religion and culture of the ethnic groups within the Empire. He improved the way of the king and made Aramaic a common language. He divided the whole country into 20 regions and ruled with Satrap officer. The Jews captured in Babylon was also released. The Jews who came back to Jerusalem compiled the Old Testament. This book is their foundation.
Poleis in Greece formed a Delos alliance under a hegemony of Athens and fought against Persia. Persia was destroyed the large fleet in the battle of Salamis and was forced to withdraw. Persia quitted the advance to Greece. Greek poleis, mainly Athens, had prospered. In Athens that established the Republic, Greek philosophy represented by Socrates, Plato and Aristotle was established. On the other hand, it conflicted with Sparta which was a totalitarian regime. The confrontation between them developed into a Peloponnesus war and led to the decline of the Greek society.
Filippos II stood in Macedonia, which was occupied by the Persian empire. He made a powerful army with the tactics composed with heavy infantry and cavalry, then in BC 336, conquered Greece under internal conflict. Although Philipps II was assassinated, his successor Alexander destroyed the Achaemenid dynasty Persia which was the center of the world at that time. He made an expedition to the Indus River. Alexander got the territory of the former Achaemenid dynasty Persia, but he had gone in young age. The vassal lords of Alexander gained independence in each region, and the Hellenistic countries were formed. Hellenistic culture blossomed around Alexandria city in Ptolemy dynasty in Egypt.
On the other hand, Rome, which was only one city on the Italian Peninsula, established a political organization with the law and the Roman Senate. It unified the Italian peninsula. In BC 146, Rome destroyed Carthage, the other crucified player of the Mediterranean. Rome unified the Mediterranean coast in around 100 years, with Hellenistic countries as the territory. The enormous Roman Empire put an Emperor, organized the bureaucratic organization, organized specialized armies. Rome made political control thoroughly outside of Italian peninsula as the provinces.
In India 2,500 years ago, small nations rallied, Kosara and Magata countries were the biggest two. The invasion of Alexander to India has created a unified momentum and has brought the appearance of a unified nation in India. Chandragapta lifted himself from the castle's low class and became a warrior of the Nanda dynasty. At the confusion of Northwest India by Alexander's army, he destroyed the Nanda dynasty, established the Maurya dynasty. Chandragapta expanded its power from the Ganges River basin to the south of Afghanistan and the Indian peninsula, and built the first unified state in India. The 3rd King Ashoka was the manifestation of the heyday of the Maurya dynasty. He became an enthusiastic Buddhist follower and encouraged and protected Buddhism. The Maurya dynasty declined rapidly after the death of Ashoka. Since then, many states of small powers repeatedly rushed in India.
In China, economic development is remarkable due to popularization of iron tools, each country competed against each other by accumulating power. In BC 403, after the Zhou dynasty went out, seven influential Lords in the Zhanguo period fought each other. The kanji that had been monopolized by Zhou spread out throughout the country due to the collapse of Zhou dynasty. Qin dynasty became powerful, which was located in the remote frontier of the west. In BC 221,the Qin dynasty destroyed other countries in China. The King of the unified dynasty is Sei. He became the king at the age of 13, and began to manage at the age of 21, and achieved unity at the age of 38. He called himself "Emperor" (the First Emperor).
The First Emperor made a centralized system to dispatch local governments to govern and stopped domination by clan relationship. He did revolutionary big projects such as unification of weight balance, money, and letters which were different for each country. But the rebellion increased against his brute forced method, the nation was disturbed after his death. Liu Bang (Gaozu of Han dynasty) re-established kingdom and succeeded the measures of the First Emperor. In Han dynasty, the Emperor Jing and Wu stood after the internal bloody battle, and they established Han's heyday.
In the northern part of China, there was Xiongnu with a strong cavalry army. The First Emperor built a Great Wall against them. Gaozu of Han were almost killed at the expedition to Xiongnu. In the case of the Han dynasty, Jing and Wu Emperor attacked Xiongnu and weakened their power. Han took in to the division of Xiongnu latter and drove it to the west. Military actions against Han's fellowships have brought information of the countries of Central Asia of that time and are recorded. Wang family got the power in Han, which a mother of the Yuan Emperor belonged, who pushed Xiongnu away. In AD 8 years, Wang became the emperor, by going away the Han's Emperor
AD 0 - 500 years: Compilation projects of holy books were held. The environment was cooled at around AD 300 for more than 500 years. Races with horseback people moved to the West globally, especially in Europe, it was the great movement of Germanic people.
The Roman Empire celebrated its heyday. The largest version is; England, Rhine, Borga River in the north, Mediterranean coast north of the Sahara desert in the south, Iraq in the east with battles with Parthia and Sasanian Persia. However, dispatching troops for the conservation of the territory and power battle went the Rome havoc, the senate system collapsed. Rome shifted to the centralized politics to the Emperor. After the transition to the tyranny, the Emperor Diocletian began divisional rule. Emperor Theodosius used Christianity as a national religion in order to utilize the organization network of Christianity in 380 years. In 395 the Roman Empire split into the east and west.
Xiongnu lost in war against the Han Empire and escaped to the west. Xiongnu appeared in Europe as Hun tribe. They conquered the East Goths who lived in the North Shore of Black Sea across the Don River in 375 and oppressed the West Goths. At that time, Germanic tribe of an undeveloped tribe lived in the European frontier of the Roman Empire. The government of Germanic people was based on blood relationship, with looted-type agriculture and hunting as industries. Pressured by the Huns, the Germanic tribes entered the confused Roman Empire. In 476 the Western Roman Empire was destroyed by army led by Okeador. The Western Roman Empire with a low degree of culture was divided by the Germanic tribe into the Kingdom of the Western Goat, Kingdom of Vandals, Kingdom of Burgund, Anglo-Saxon 7 Kingdoms, Frank Kingdom, East Gotha Kingdom. It is the prototype of the current Europe.
Large religious books were compiled between AD 0-500. In AD 77, Avesta of Zoroastrianism which became the state religion of Sasan Dynasty of Persia. The Buddhist scripture was translated in the book from the previous oral messages at the King of Kanishka (around AD 130 - 170). It is said that the New Testament was formed around AD 150. Buddhism spread to northwestern India during the Kushana era in the first to third century. Buddhism came there up with the faith of Zoroastrianism, Brahmanism, Jainism, Greek/Roman gods. Mahayana Buddhism was created by Nagarjuna, from religion originally only for priests. Mahayana Buddhism has a philosophical structure that can encompass various religions, and became the driving force behind Buddhism's spread internationally. In India, Buddhism was absorbed in Hinduism (philosophically approaching). There, Vairocana and Brahman are identical.
In India, after the confusion period in which the Maurya Dynasty collapsed, the Kushana Dynasty which was an invader from Iran was established. Buddhism prospered with the protection of King Kanishka and created Gandhara art. The Kushana Dynasty declined in the fight with Sasan Dynasty of Persia, and in exchange the Gupta Dynasty (around AD 320 - 550) was established. Under Gupta Dynasty Buddhism faded.
The East Asian society had double-layered structure of the Chinese hegemony order and the similar order of neighboring countries. In China, Emperor Kuang-wu killed the Emperor Wang and the Han Dynasty revived (AD 25). The territory became the largest at the time of the next Emperor Ming and diplomacy was actively carried out. After that the emperor continued ninth generations by relatives and eunuchs. Han did not recover. The powerful people of various places fought with the Yellow Turban Rebellion (AD 184), it became the Three Kingdoms era. Liu Bei, Kanu, Zhang Fei are famous for their Three Kingdoms. Wu (Sunkuan) and Shu (Liu Bei) united against the biggest power Wei (Cao Cao) and fought against each other, Liu Bei died (AD 223) due to split of fellowship. Zhuge Liang (AD 181 - 234) who succeeded Shu's real power dispatched against Wei, but Sima Yi prevented them. Mr. Sima held power, destroyed Shu, Wu and established West Jin. During the Chinese chaos, the surrounding ethnic groups (Five Barbarians: Xiongnu, Jie, Xianbei, Di, Qiang) entered North China. Starting from Former Zhao by Xiongnu, 13 countries rose during around 100 years. At the end of era, the northern Wei (AD 386 - 534) of Xianbei was prosperous. In South China, the three nations of the Han Chinese were established in turn. The reason why the unified dynasty was not established is that the power of local rulers was strong.
Teotihuacan civilization (BC 250 - AD 400) and Maya civilization (AD 250 - 900) were established in Central America. Teotihuacan ruins are including the pyramid of the moon, the street of the dead that extended to the east and west from the pyramid, the pyramid of the Sun along the street, Quetzalcoatl temple at the end of the street. It was estimated to have a population of 100,000 and dominated central Mexico. Teotihuacan may have been a group rule like the Roman Empire, not a royal government. Maya civilization is famous for Acropolis temples in the center of Copan ruins and Tikal ruin. A long-term calendar and a Mayan letter inscription engraved on a stone remained, and many city-states flourished around the central and southern lowlands. The royal system that adopted the advanced culture of Teotihuacan was their basis of politics. Unlike the so-called four major civilizations of the other continents, the civilizations of the Americas did not use the large river. Many cities flourished in the tropical rainforest. It was a city civilization in Neolithic age without metal instruments such as bronze ware nor ironware. They did not have domestic animals such as cattle and horses. The wheel was not put to practical use. Because of that, the dynasty which unified the whole region was not born.
AD 500 - 1000: Global warming occurred mainly in around AD 900. The activities of the northern ethnic groups had increased. The area that nations were established expanded toward the North.
In the UK, after the Roman Empire withdrew, seven countries of German, consisting of Anglo-Saxons, were fighting against the Celtic country. Essex unified England in 829. After that, UK invaded by Viking. Several German countries and the Byzantine Empire (East Roman Empire) were fighting in the central part of Western Europe. The Kingdom of Frank has expanded his powers. The King Carl (reign 768 - 814) expanded the domain to France, North Italy and the western part of Germany at the time. The Byzantine Empire also strengthened its power from the Balkans to Southern Italy. The Kingdom of Frank and the Byzantine Empire became the military background of the conflict with the Roman Church and the Constantinople Church, which became Orthodox faith. The Kingdom of Frank was divided into three countries by the grandchild of Carl the Great in 834, into the West Frank Kingdom (France), the East Frank Kingdom (Germany).
In 610, Islam was established with Muhammad as a founder on the Arabian Peninsula. Muslims built a caliph country and destroyed the Sasan dynasty Persia who had fought with the Byzantine empire. After Muhammad, the caliphate was elected and lasted until his fourth generation. In 650 the only Quran was compiled. Moawiyah assassinated the fourth caliph, Ally, and established the Umaiya dynasty. Muslims have divided into Shia Islam who do not recognize anything other than Ally as a valid caliph and Sunnah Islam who accept other caliphs. Islam may be the result rather than the cause of the Arab conquest. Both Christianity and Judaism claim similar historical grounds. The religion insist that there was an inevitable reason for its birth, and that became history.
The Umaiya Caliphate robbed the territory in North Africa of the Byzantine Empire, expanded its territory to Iberia Peninsula, Morocco at the west and to Iran at the east. Later on, the Abbasid Caliphate pushed the Umaiya Caliphate away. The Umaiya Caliphate moved its capital to the Iberian Peninsula. In the Abbasid Caliphate they introduced paper technology through the war with Tang. They translated Hellenistic culture and Chinese classics and constructed a huge library. Shia Islam founded the Fatimid Caliphate mainly in Egypt. The economy developed in the Islamic cultural area, a culture blossomed that blended Greek, Hellenism, and the heritage of India.
In the height of the Abbasid Caliphate, Islamic merchants used Dow ship to create a worldwide trade network. The center of the network was Bakudat. When they went to the west, they entered the Mediterranean from Damazukus, went through Tunis, Cordova, throughout the Atlantic, to Tombuktu in West Africa. When going south, to Mecca from Persian Gulf, Aden, reached to Malindi and Kilwa in East Africa. When going north, from Samarkand to Chang'an via Kucha (Silk Road), or from Constantinople to Kiev. When going east, cross the Indian Ocean from Calicut to Malacca, to Guangzhou and Yangzhou of China. It is the world of Arabian Nights story.
In India the Hindu kingdoms had battled each other repeatedly. In Southeast Asia, the conquest dynasty developed due to the influence of civilization in the Indian sphere. The influence of India was presumed from the transmission of letters. Cambodia's Angkor Wat (around 800) is famous as the ruins of this time.
In China in 588, Yang Ku established the Sui dynasty and put an end to the era of Sixteen Kingdoms. Sui dynasty was short lived because the Emperor forced large scale civil engineering works and wars. Then Tang dynasty (618 - 907) was founded. Tang dynasty developed into the global empire, its territory was to the west to Turkestan. It was because the foundation necessary for maintenance and operation of the empire was established in the era of the Sixteen Kingdoms. First, the ranking system of the executive branch (nine class system: incorporation into the regime of local strong ruler) was established, then it moved to a clan (a government official appointment system by examination). The Chinese examination system was a selection system that guarantees fairness and objectivity. It also established the land ownership mechanism and collect taxes (Equal-field system). The bureaucracy was set as the three ministries plus six divisions which was the system of three powers under the emperor. Paper technology made a big contribution as a medium for recording and transmitting information to support the bureaucracy. Tang dynasty was destroyed in 907. After that, the Dynasty diverged in the north and the south, the two major cultural spheres named the fifth generation ten countries were established.
In the Eurasian grassland region, new nomadic forces from Eastern Siberia, such as Mongolia and Manchuria, appeared one after the other, and they moved to the agricultural area in the south and the grassland in the west. In Central Asia, the Turkic people first expanded their forces and founded Gokturks dynasty. They built a great empire ranging from the west the Aram Sea to the east to Manchuria, and conflicted with the Islamic empire or Tang dynasty. Gokturks was annihilated by Uighur of the same race (744 - 839). Then, the Kyrgyz ethnic group is founded. In Manchuria, after the Tang faded, Liao (916 - 1125) was founded. The founding movement came active in Japan and Korea, and the conquest dynasty was formed respectively.
Maya civilization celebrated in Central America. Many cities representing Teotihuacan have been built. But suddenly the city was abandoned from the 820 to the 889 (the last date of the monument). The cause may have been written in the book incinerated at invading of Spain and Portuguese. Analysis of the annual stripes deposited on the Cariaco Basin on the coast of Venezuela revealed that discontinuous but severe drought occurred several times at the time of the destruction of Maya civilization. There were 6 droughts in 9 years from 810, then 3 years from 850 and lastly, three droughts during 6 years from 910, hit the Maya civilization. No matter how flourish a civilization goes, but when food shortages continue for three years, it would collapse. After Maya civilization, the Torteka people advanced.
The characteristic of the African empire is that it disappears from the map without invasion and occupation by another country. List of African empires.
1,000 - 1,500 year: The birth of a global society
The Iranian Buyid dynasty invaded the capital city of Abbasid dynasty, and in 945, the caliph of the Abbasid became a mere facade. In 1055, a Turkish Nomadic, Seljuq Turkey, in the Central Asia released Bakudat from Buyid dynasty. Abbasid caliphate appointed the King Tughril Beg of Seljuq Turkey as Sultan and allowed to administer as an authoritarian state. Seljuq Turkey entered Anatolia and oppressed the Byzantine Empire.
In Europe, living Germanic ethnic groups were under aggression of Viking from the North, Islam from the South, Majar people from the East. European countries began to function as a national group centered on the Western Roman Church. The Pope of Byzantine Empire asked Western Rome church for assistance against Muslim invasion. European countries pretended to help the Pope, and formed the Crusade to invade the Middle East region for a new territory (1096 - 1270). Initially the Seljuq dynasty was in a state of division so the Crusader occupied the eastern coast of the Mediterranean. Jerusalem was plundered, the inhabitants were massacred, the kingdom of Israel was founded. Saladin who set up the Ayyub dynasty (Kurdish) organized army and kicked out the Crusaders (1187). Although the crusader's invasion continued thereafter, the Ayyub dynasty that the capital city was Cairo and then Mamluk sultanate repelled them all.
The period from 800 to 1300 was a mild temperate period of global warming. Viking was active in Europe, from England to France, to the Mediterranean. The Kingdom of Sicily is a Norman country. They went to the west for Iceland and Greenland. Viking, who explored North America, was Reef Ericsson, and his mythology remains. It was about 500 years ago of Columbus’s voyage. Viking headed to the east established the Kingdom of Novgorod, and Kievan Rus'.
The Turkish ethnic group worked as a foreign soldier in the Abbasid dynasty. They determined Muslim as the state religion, established the Karahan country in the Central Asia. They also reached the Ganges river basin of India and established the Ghazna dynasty, the Goal dynasty in the 13th century (Delhi sultanate dynasty, 1206 - 1290). Since then, conflict between Muslim and Hinduism began in India.
The Slave dynasty was held in India in the 13th century by Aibak. Since then, until the Mughal Empire of the 19th century, the Muslim dynasty dominated in India. Muslims were open to other religions, so Indian domestic religions never went out.
In China, Zhao Zhengu established the Song dynasty (Northern Song) after era of the fifth generation ten countries. His brother Zhao Ming was reunified China in 979. Song dynasty was pressed by the northern ethnic Liao and Jin dynasty, but Song had governance by law and reason rather than by military force. Its culture had prospered greatly. Especially since the South Song (1127 - 1279), the development advanced in Gangnam, agricultural production improved dramatically. Special products such as tea, ceramics, silk were born. Merchants dealing products had political power, and economic systems also developed. Compass, gunpowder, and printing technique were invented. Cheng Zhu school which summarizes the Chinese thought and respects a rational mind was born. Weapons using explosives invented in China were developed in the war between Song and Jin, and evolved as weapons to throw fire. Mongolia used these firearms and improved explosive bullets.
It was Mongolia that oppressed Muslim countries after the Crusade. The Mongol army led by Genghis Khan destroyed the West Liao dynasty, obtained key cities of trade in Central Asia, destroyed the Kingdom of Islamic Horasm which dominated Central Asia and Iran (1231). The Mamluk sultanate won Mongolia and prevented the invasion of Mongolia to North Africa. After conquering Eastern Europe, Russia and the Middle East, Mongolia began to invade into China of great powers.
Mongolia beat Jin dynasty (1234), destroyed the South Song (1279). Invading Korea and Vietnam, it also attacked Japan. At this point, a large area from Eastern Europe to China was to be tied up in the Mongolian Empire's transportation and economic system. Islamic culture, science and technology of West Asia was transferred to Han Dynasty. When the expedition of Mongolia ended, Arabian, Iranian and Turkish Muslims moved to China one after another. They were called Semu, estimated to over 1 million people. Mongolia retreated to Central Asia when Red Turban Rebellion occurred in China. After that, the Timur Empire took over Central Asia and in the Middle East Ottoman Turkey expanded its influence. Ottoman Turkey, founded in 1299, was one of the local governments, but organized a powerful army and advanced from Anatolia to the Balkans. Once destroyed by the Timur Empire, it was revived and restored its territory. Mehmet II in 1453 fell Constantinople and destroy the Byzantine Empire.
In Europe, the merchants in each city on the Mediterranean coast accumulated property since the crusade activity. Greek and Arabic literature was translated into Latin in the 12th century. The Islamic scholarship, which was at the highest level in the world at that time, was transplanted to Europe and Renaissance of the 12th century started. The modernization of Europe can be thought of as the result of people moved to the South due to transition of climate from warm to cold. The kingdom was centralized while the powers of the Pope and the small owner were weakened. Europe was not invaded at last by Mongolia having its domestic problem, and also by the Timur empire. However, the Nomadic tribes were still a major threat to Europe and prepared a military regime for their invasion.
In North Vietnam, Lee Dynasty was founded. The Pagan dynasty established in Myanmar imported the hinayana Buddhism from Sri Lanka and made it the state religion. Buddhism was transmitted to Thailand, Cambodia and Laos.
In Central America, the Tortekas came to hegemony until the year 1200 after the Maya civilization. After that, the Aztec empire invaded and the Central America was under Aztec until the Spaniard destroyed the Aztec empire. The Cusco Kingdom was established in the 13th century on the Pacific side of the Andes Mountains in South America. It was united as the Inca Empire by the King Pachacuti in 1438. In the heyday, there were 80 ethnic groups and a population of 16 million in Inca Empire.
The plague struck the countries united by Mongolia. The plague, which was endemic to the steps of Central Asia, reached China in 1345. It struck Constantinople in 1347, was brought to Genova and Venice by ship, and spread to Europe the following year. It has killed one-third of the population of Europe and China. This plague shook the feudal system and brought about a more fluidic society.
1500-1900 years (Asia: from 40 degrees east longitude to 160 degrees west longitude): The empire system with hereditary leaders has Limited prosperity.
Ming (1368 - 1644) was established in China who kicked out the Mongolian people. Advanced bureaucracy based on the rule of law was set up, and a tyranny was born. After governance by Emperor Yongle, its heyday period, domestic politics were appropriated by mediocre emperors. Disturbance by neighboring ethnic groups often occurred. However, the national consciousness of the Han people greatly increased.
Manchuria constructed political power over three generations from around 1600, dominated China by the corruption of Ming regime, and established Qing (1636 - 1911). The era 140 years of Kangxiang, Yongzheng and Qianlong Emperor were at their peak. The Manchu people became Chinese civilization about politics, economics, and culture, but forced to the Han people through clothes and hair styles. Resistance of the Han Chinese continued long, and Qing has expanded the territory at every time it drove resistances away. Many Han people became displaced people, and formed an overseas Chinese society mainly in Southeast Asia.
Russia was under Mongolian rule, but in 1480 the Grand Duchy of Moscow became independent under Ivan III. Russia culture was a Central Asian style. They converted farmers into villeins and built a tyranny. At the time of the next Ivan IV, he expanded his territory, hired a Cossack soldier and advanced to Siberia. After this, confusion continued for a while, Romanov dynasty was established, especially Peter I (1682 - 1725 years) changed Russian culture to European style. Russia entered the Baltic Sea, had a war with Sweden to build a port town of Petersburg. It also signed a treaty with Qing, thus obtaining control of Siberia.
In the 15th century, a huge and complicated trade community network appeared with autonomy from the coast of China to the Indian Ocean. Even if the state power was trying to control them by force, they fled to the sea, shifting their base of activity to a distant port far from the state power. This network is composed of mainly Muslim, local people, China, and Hindus. Japanese pirate, which has mainly exercised power in the East China Sea from the 14th century to the 16th century, is one of them.
In East Asia, there was a principle that the rulers guarantee security and equal trade opportunities in the trade zone and leave the problem handling to merchants and residents to their autonomy. From the 16th century Europeans came to appear in East Asia from South Asia and Southeast Asia. The Portuguese brought in maritime control. Fearing the Hideyoshi's approach to the south, Spain will send a battleship to Taiwan in 1598. It was 1597 years that Ming took the troops stationed in Penghu Islands in preparation for Hideyoshi's southward movement. Europeans succeeded in industrial revolution in the 18th century, developed low-price textile products, gradually dominated the commercial network. After that, with the backdrop of armed force, European politically intervened in the unstable period of Asian countries, expanded their colonies.
A ban of pirate policy was implemented to crack down on Japanese pirate activity. This is the origin of closure of Japan. In Japan, the closure policy is for the Shogunate to monopolize relations with foreign countries, and it excludes Christianity related powers which can be said to be the essence of Western culture. The selective acceptance was strengthening of foreign culture by the Shogunate. Closure policy was never a system to block all external relations and reject foreign culture.
Descendants of royalty of the Timur empire invaded northern India from Afghanistan and built the Mughal Empire (1526 - 1858). Although the royal family was Muslim, it adopted a consolidation measure against the Hindus and expanded the territory to the south. Aurang Zebue (ranking 1658 - 1707) conducted Islamic-centered politics, inviting resistance of Hindu and other religions. British intervened in that turmoil, the Mughal Empire became a colony of UK.
Ottoman Turkey fell Constantinople in 1453. They determined the city as their capital and renamed as Istanbul. It expanded the territory to Egypt, Iran, seized governance of the Mediterranean Seaside and approached Eastern Europe. The Ottoman Empire kept pressing on Europe for a long time, maintaining a powerful force. In 1922, the Sultan system was abolished with the democratization revolution of Turkey.
In a major cultural area with a long history, a new state was born even if confusion occurred, the central government was immediately recovered. In stable society, merchants are guaranteed property, so credit transactions were smooth and active. The developed transport system, a unified money system allows merchants to operate in a wide area. Besides currency that was functioning only in daily transactions within the region, the currency necessary for settlement was set between long distant regions. Gold or silver was used as the material for such a currency and gained consensus as an international currency in a wide area. Accumulation of wealth was promoted after expensive currencies circulated. As the bureaucracy matures, it restricts free trade and international exchange to maintain domestic order.
1500-1900 (other than Asia: from 160 degree west longitude to 40 degree east longitude) European countries got super power and started to reform social structure on a global scale.
In the historical view of Europe, the era of the great voyage began at the end of the 15th century. However, it was a very small scale. European adventure team crossed the Pacific Ocean about 1,000 years after indigenous people of Micronesia and Polynesia made a voyage. Since Ottoman Turkey was a great diplomatic enemy, Vasco da Gama managed to discover a route to India through the Independence Peak of Africa. The Santa Maria was a so small ship that Columbus got on and found the American continent, which was only about a sixth (one sail) of the ship that Zheng Hu had sailed to the east coast of Africa 100 years before Vasco da Gama. Zheng Hu led a fleet of 1,000 vessels.
Ottoman Turkey was the biggest military threat to Europe, on the other hand, played an important role to grow Europe countries socially and culturally. In addition to the support of the Renaissance by cultural exchanges, Ottoman Turkey interfered with the internal conflict and religious reform in Europe.
The year 1492 is a memorable year for Spain. Spain displaced the Islamic forces from the Iberian Peninsula (Reconquista). Also, Columbus arrived at the America continent which opened the way to enter the America continents. In 1533, the Inca Empire was destroyed. The kingdoms of the America continent without cavalry and iron-making technology succumbed to the pressure of Spain. The Inca Empire was looted by a large amount of gold and silver, the people enslaved by mining development and farm management by Europeans. It resulted the population of the continent decreased to one tenth. Spain plundered a large amount of gold and silver, but practically it only improved the trade deficit against Asia and Islam.
Around 1540, the firework gun developed in Spain transformed the ways of the wars. On behalf of a well-trained cavalry party, civilians with guns became the main power of solders. The horse-riding nomads ruling actively in Central Asia were completely sealed up. Europe has advanced to the world centering on trade with a background of military force. East India Company was established around 1600. European countries have come to interpret the world with Christian standards. Therefore, Europeans clearly distinguished, discriminated, and disrespected to the world deviating from their standard. It is a basis for physically consolidating the residential area of other people as its own area. European countries have expanded their dominant regions in Asia and forced the natives of their values.
Europe has supplied labor from the African continent for the development of the America continents. Triangle trade, exporting goods from Europe, buying slaves in Africa, exporting slaves to the America, buying sugarcane and cotton etc, and processing it into industrial products in Europe, is particularly profitable. Europe increased its economic power and technology to the world level. On the other hand, Africa's population was said to reduce by one third.
Europe was a backward region, and was struck by the invasion from the East regions and the wave of the global monetary economic system. Now Europe became equal to Asia in the 1700s. Europe has developed its own culture since the Renaissance. They invented three fundamental concepts, human rights, capitalism, and scientific methodology.
Europe created a system other than the monarchy for governance of the state. Until then it was common sense that the conqueror would become the king. The foundation of new government was born in the UK, the United States without the king (1776). In France, the revolutionary army executed their king (1793). The democratic state was managed by administration under Congress. The concept of public was born, fundamental human rights were invented. On the other hand, the war became a work of the people, the war itself became a harsh political act. With the emergence of a national war, European countries colonized the other world against their background of strong armies. In 1840, Opium War. In 1877 the UK colonized India. Only colored race who kept complete independence at the beginning of the 20th century was Japanese.
In the United States and Europe, black people became absolute lower-class citizens who were abandoned African culture (by being destroyed) and brought to the America continents and Europe as slaves. Yellow races were able to act as a citizen who can compete equally with Caucasian because their home culture is preserved. At the time when the Chinese began immigration, they were under pressure and discriminated. After slavery was abolished, Asian immigrants to the US increased rapidly.
The Japanese archipelago stretches over 4,000 km from north to south, and there is archaeological and anthropological evidence that humans have lived there for more than 30,000 years. Currently, three ethnic groups, Ainu, mainland, and Ryukyu, are distributed in order from the north. It was the descendants of an old type of Asian population who lived in Southeast Asia that emigrated to the Japanese archipelago and formed the Jomon people about 15,000 years ago.
The distribution of various precious stones in the Jomon period was about 200 km from the production area. For example, obsidian, which is hard and smooth and is the best stone tool material, is not found so common. The known production areas are Shirataki in Hokkaido, and Kozushima in the Izu seven islands in the Kanto region. Obsidians produced in Kozushima have spread all over the Kanto region until about 3,000 years ago. Kozushima has never been connected to land even during the Ulm glacial period, so people needed a ship to get obsidian. 200 km was the range of daily exchanges such as logistics and politics in the Jomon period.
The Amano-Iwato myth is said to be a memory of a solar eclipse. However, solar eclipses are not so rare and do not cause any damage. It wouldn't be handed down as a myth. Imagine that the prototype was the eruption of the Kikai Caldera 7,300 years ago. Volcanic ash covered the whole of western Japan and probably covered the sun in the short term. West Japan is a region that would become the prototype of the nation later, and is also the place where the ancient affairs were compiled. The eruption of the volcano was not felt directly, but it is provable that a cloud of black ash would cover the sky. It was a large eruption that turned Southern Kyushu into a land of death, but although it caused disasters in distant regions, survived people inherited the story. The myth peculiar to Kojiki is considered to be the memory of the Jomon people.
In the Jomon culture of Japan, we created a system that allowed people to settle down by collecting, hunting, and fishing. A variety of cultures and societies have emerged due to the natural environment of the region and each cultural tradition. A village was built at the Sannai-Maruyama site in Japan for 6,000 years.
About 3,500 years ago, the Han Chinese group arrived in northern China, oppressing the indigenous people in Yangtze River basin. The Han Chinese founded the Shang dynasty. The people of the Yangtze River basin spread to Japan, Southeast Asia, and Polynesia. Immigrants to Japan had different morphologies from Jomon people such as faces due to cold adaptation. The Yangtze River people brought the technique of paddy rice cultivation to Japan. The advent myth of Emperor Jimmu in Kojiki and Nihon Shoki seems as memory of this migration. Due to the civilization they brought, they moved to the Yayoi period. After the Yayoi period, migrants via the Korean Peninsula settled from northern Kyushu, moved on the coast of the Japan Sea to the Kinki region in Honshu. they repeatedly mixed with the descendants of the indigenous Jomon people and became mainlanders. However, the descendants of the Jomon people in Hokkaido were separated as Ainu people after almost no mixed blood with the migrants. The Ainu are likely to be mixed with the peoples around the Okhotsk Sea. The Ryukyu people in the Nansei Islands, centered on Okinawa, were also a unique ethnic group mixed with the ethnic groups of the southern islands. Ryukyu people are not as clear as the Ainu because of the large number of immigrants from the mainland since the Warring States period. They retain the characteristics of the Jomon people more strongly than the mainland people.
Japanese and Korean are Paleo-Far East Asian languages and belong to the Altaic language family. There is a language similar to Japanese in the Tamir region of South India. In addition to the language system that the Jomon people had, Japanese was formed by incorporating words that entered via the Korean Peninsula. The historical era of Japan began with the import of Chinese characters in the 7th century. The import of language is also the import of culture. Japan was strongly influenced by the Chinese civilization. However, due to the wars in China and the Korean Peninsula, trade was often closed. As the sea separated Japan and other Asia, the Japanese formed a unique culture.
From the latter half of the Muromachi period, the Japanese shogunate and Fudai Daimyo traded and made huge profits. The disorder of the balance of power against the background of the profit caused the Onin War, which in turn caused the Warring States period. The Tokugawa Shogunate, which ended the war, banned the free trade of Japanese people for several reasons and adopted a so-called seclusion system. The direct reason is the prevention of Christian missions. Christianity was the first powerful religion since the introduction of Buddhism. In addition, as missionaries brought in their own colonial policies, diplomatic relations were abolished with Spain and Portugal, and other Catholic countries. In addition, big trade would flourish commerce and industry in the daimyo area and wealthy commerce. If they would become huge, there would be a risk that the shogunate would be relatively weakened. There, trade was controlled and foreign information was monopolized by the shogunate. However, instead of closing the door completely, information was actively gathered, and officials of the Shogunate were dispatched to investigate if necessary.
The Edo Shogunate at that time had world-class military power, so it was able to adhere to its own policies toward other countries. Although China and Korea could not be as thorough as Japan, they adopted a seclusion system to stabilize their countries. At that time, many of Japan's imports and exports were munitions such as raw materials for gunpowder, and weapons themselves were also imported. Since the Taiho Code, cows and horses have been valued as a means of production in Japan, so it was forbidden to slaughter them just for leather. Leather was imported in large quantities from Southeast Asia. A few necessities were imported through the Netherlands.
Until the Edo period, Japan was the world's largest producer of gold, silver and copper. According to Arai Hakuseki's Oritaku Shiba no Ki, in the latter half of the 17th century alone, there produced 2.4 million gold, 370,000 pieces of silver, and 70,000 tons of copper. Since gold was more abundant in Japan, the exchange ratio of silver and copper was different from that of other countries. As a result, foreign exchange trading was active, and one-quarter of domestic gold and three-quarters of silver flowed overseas.
I made summaries on the history of human beings every 500 years, focused on way of thinking. Current human beings were born in Africa approximately 200,000 years ago. We stayed in Africa a hundred and several tens of thousands of years, we spread to the continents of the Earth. Since the climate has warmed up, we established agricultural technology (10,000 years ago). We invented the use of letters and metals to create cities and communities (6000 years ago). Technology and knowledge have been accumulated and systematized in the state (2000 years ago). People explored knowledge and skills and organized the wisdom they got. And modern scientific knowledge was highly organized (200 years ago). It can be said to be a period of great revolution.
Through these times, human beings have not changed as species. There is no big difference in intelligence. Therefore, the human who went south of Indian continent 30,000 years ago, the Dravidian warrior who faced the invasion of the Aryans 3,000 years ago, the merchant of the Mughal Empire which had traded with the British merchant 300 years ago, an Indian physicist who observes the fate of elementary particles by driving a synchrotron, all belong to the same species.
Since all human activities are never preserved, we cannot deny a possibility of existence of the destroyed civilization. During the history of human beings of 200,000 years, if it allows a time of progress for only 5000 years, there is a possibility that some people built a civilization of 200 years ago somewhere on the Earth. However, when becoming a civilization of the modern level, even if it would have been destroyed for some reason, its footprints cannot be completely erased due to their big change on the Earth. Therefore, I can conclude there was no civilization existed in the past at the same level of contemporary one.
The influence that human being exerted on the Earth is more abrupt than the change caused by living creatures before the human race, crustal deformation, and meteorological phenomena. In the earth history, it took thousands of years for the grassland to become a large forest. In addition, stable forests will continue to exist in the order of tens of millions of years. Human beings plant trees to convert the grasslands into forests in hundreds of years, and conversely turn the large forests into grasslands (ranches) in decades. The biosphere cannot keep up with the environmental change caused by human activities, so to speak, the extinction of species in present days is equivalent to the mass extinction in the past.
Since mankind has invented agricultural technology to control natural energy circulation, they have created their living area in the ecosystem on the Earth. Understanding of the natural world is indispensable for maintaining their living area. Since the method of understanding has shifted from religion to natural science, human beings have become able to expand their living area more efficiently. We have maintained the living area by scientific principles, only about 200 years ago. However, the change is rapid. The values of scientific civilization have already entered the period of comprehensive evaluation.
Until now I have described along the flow of history, but as the information volume becomes enormous as approaching the present age, it is difficult even to summarize. The history in the world is usually described as the history of politics, therefore the history of the war between the states. Politics is treated as small as possible in this thesis, and instead chose the foundation of contemporary civilization as a topic. I will outline as the development of basic technology in each field of energy technology, chemistry, agriculture, medicine. After summarizing the history of war, I will look at urbanization, democratization, the Internet which is the result of complex technology. Then I will look at the remaining 21st century as the near future and conclude with a summary of the future of the Earth.
Perhaps in 95% of the time since the human race was born, the main power source was human. Thousands of years ago, we got more power when capturing large mammals such as cattle, horses, or buffaloes, into human society as livestock. Livestock has greater output than humans, but rearing management of them is necessary, and control of them is difficult. Humans were still necessary as power sources. Large mammalian livestock was mainly used as a means of transportation, and it also became food.
Next, a water wheel, windmill, and sail were invented. A description on the water wheels is preserved in Greece around the 1st century BC. I could not find the oldest windmill, but it will be in the same time and area as the waterwheel. A power unit that uses natural energy saves human labor in a simple operation for a long time. However, the amount of water in the river or the wind was influenced by natural conditions, and there was a defect in the stability of the output. Still, they became widespread, improved and used around the world until steam engines, internal combustion engines became common.
Steam power was put into practical use in the 18th century with the change that parts of various machines became iron. In the early days of the Industrial Revolution, steam engines and steel industries fueled wood. Eventually, when the forest decreased, the fuel turned into coal. Especially in the UK, there is a large vein of coal and iron ore, and two resources are tied together. An inventor, Mr. Watts improved the steam engine and put it into practical use. After that, it was incorporated into a steamship, a steam locomotive. Coal was used in coke furnace for ion manufacturing, production amount of ion increased at a stroke. Steam power was available even without river and wind, so we could make factories even in cities. We were able to consolidate production activities as factories by supplying power in cities.
In an agricultural society, we can barely make foods we eat, but there is little left to feed others. Therefore, very few people have extra energy to build castles, coats, and armor. The use of cows, horses, wind and water produced a small amount of surplus energy, but not much. The Industrial Revolution has dramatically increased the amount of energy per worker. The surplus energy has built houses, machines, software and tools that enrich our lives today.
The power plant is basically an energy conversion device. The windmill transforms the kinetic energy (wind) of the air into rotational motion of the shaft. Water turbines also convert the positional energy of water into kinetic energy. The steam engine converts (burns) the chemical energy of fuel into thermal energy, creates steam, and the controlled expansion of steam is converted into kinetic energy. The internal combustion engine explodes fuel in the confined cylinder and transmits the expansion energy to the piston. That is, the chemical energy of the fuel is converted into the kinetic energy of the piston for use.
An internal combustion engine has put into practical use in the latter half of the 19th century. It was a power technology that can be downsized and lightened by integrating the combustion part and the engine part. Internal combustion engines have been applied to various applications. Especially automobiles and ships have developed as transportation power. We have changed the trade of the world while infrastructures were prepared such as arranging roads and gas stations, and large harbor, Suez Canal, Panama Canal and so on.
At the same time, an electric power generator was invented. Wind power, hydraulic power, steam engine, and internal combustion engine are also used to turn the generator, converted to electric energy to be used. Nuclear energy was also added in the 20th century. Electric energy requires initial investment in infrastructure such as transmission line, but because of its low cost of transportation, small size of power plant, and high safety, it has spread rapidly.
Furthermore, batteries and accumulators that store electric energy in the form of chemical energy have been developed and spread. Batteries and accumulators are convenient to carry because they do not have to be connected with generators and transmission lines, further promoting device compactness. At present, fuel cells are being developed that directly convert chemical energy into electricity without burning.
Electricity travels through the transmission line, but it also travels in the air as electromagnetic waves. The technology which sends information as electric waves (radio waves) to a long distance via a transmission line or atmosphere accelerated the handling of information. It was 1890 that a submarine cable was laid between the UK and India. After this the submarine cable extended to China and Australia.
The international specialization supported by transportation and telegraph technology is a structure of the world history created since the era of the great voyage. International division of labor has developed in the form of supporting the industrial society of Western countries and promoted colonization of Asia and Africa. Conversely, after the Great Wars it became a driving force to raise national consciousness of each region.
The research theme of natural philosophy is matter, life, and prediction of future. Natural philosophy is trying to understand the material world, including physics and chemistry. To clarify the fundamental principle of the material world, for example, it was thought that gold could be produced. Alchemy is a technique that turns a substance into a more complete existence. Likewise, a medicine to change the human body into immortality was sought. In the ancient nation it was called an elixir. An anecdote of the Chinese emperor is famous. Medical arts for explanation on complex life phenomena and to improve the pathological condition were born in many civilizations. Astrology was established as an academic exercise to accurately predict the future with the movement of the celestial bodies. The idea that ordered motion of stars would be in conjunction with the movements of this world has brought about the concept of time to humans. It also became the basis of fortune-telling that the future is implied in various forms.
After Kepler, Galileo, Descartes and others, Newton introduced mathematics as a language to describe the law of dynamics, thus physics separated from natural philosophy. Physics is a discipline to explain natural phenomena by utilizing the results of mathematics. By using mathematics, we could explain nature more deeply, not limited to the phenomenon of real world. Moreover, it gained a calculation method which is convenient for application. The idea that celestial movements are mere physical laws has driven astrology into superstition.
On the other hand, the natural philosophy on objects and substances has developed another way. The medieval alchemist accumulated extraction techniques of various materials and created the foundation of chemistry. Gas is generated when mixing acid and metal. Hydrogen was discovered because the gas generated by the reaction of acid and metal is different from air. In the second half of the 18th century, gases such as nitrogen and oxygen were discovered one after another. By quantitatively analyzing the weight of the reacting substance and the weight of the products, it became clear that there is a certain proportional rule in the chemical reaction. The law of conservation of mass was proposed by Lavoisier, the concept of elements, atoms, molecules was also organized by Dalton.
At that time, the European countries expanded their forces and explored all over the world and gathered samples from the natural world such as animals, plants, and minerals as specimens. To record information such as the type and nature of specimens, and further to classify them is called as "natural history".
In the 19th century, the chemical reaction of matter was understood by combining atoms and their bonding, and various chemical reactions were discovered. Searching of elements began and the results were summarized as the periodic table. Also, synthesis and extraction of new molecules were carried out based on the list of chemical reactions. Chemistry is characterized as the science of understanding by the concept of molecules the myriad materials themselves existing on the Earth and the Universe, and the world where materials and life are interwoven.
At the same time, the chemical industry has spread all over the world. At first, pigment was synthesized, then explosives (such as dynamite) were synthesized. With knowledge of chemistry, it is possible to create substances that do not exist in nature and use them for industry. Chemical reactions were examined more comprehensively with accuracy far beyond by alchemists. Among them, a new industry that produces convenient substances for industries was born, and it was alchemy in literally.
In the 20th century, molecules constituting the living body were added to the analysis targets. In 1907, the world's first synthetic plastic "Bakelite" was born. Also, in order to explain theoretically the interaction of molecules, physics was introduced into chemistry, and a boundary science called physical chemistry was born. One representative product of this new area is a semiconductor that is the basis of electronics technology.
It is not too much to say that our civilization is supported by chemical knowledge. Many of the things directly and indirectly used in daily life have been obtained from the results of synthetic chemistry, from petroleum products, medicines, chemical fertilizers, semiconductors, iron, cement, plastics, synthetic fibers, cosmetics and stationeries.
Mankind has used various living organisms, such as plants and animals that grow on land and oceans as well as invisible microorganisms. Living organisms are nutrients for maintaining our lives and activities, and resources that support and enrich daily life. We have chosen a biological resource from the natural world that meets the purpose of our usages through long history. In addition, we have kept them close to us, selected desirable properties, and breed. At the same time, we have developed cultivation and breeding methods that maximize the ability of these living organisms.
The method of breeding depended on experience. Some of nature of parent are inherited to their child or sometimes not. In order to ensure stable harvest, we have bred strong crops against cold climate or pests. Mendel revealed that genetic elements behave as independent units mathematically. The units are named genes, and their chemical substances are called DNA. Genetics has extracted useful traits from a vast breeding collection and helped to fix advantageous genes (to produce breeds).
Basis for breeding of rice and wheat was founded in Japan, and new varieties of corn was commercialized in the United States. Rice and wheat are dwarfed. Plant nutrition is made by photosynthesis. It is a breed that reduces the amount of limited photosynthetic products to distribute to root, stem and leaf growth and distributes as much as possible to the grain. The allocation to grain has been raised from 20% to 50-55%. At the same time, because of its low height, it became resistant against the wind not to fall down even if the crops were heavy. It is suitable for automated harvesting. For healthy growth of plants, enough roots, sufficient leaves for photosynthesis, and sturdy stems are required, so modern dwarf species is considered to mark the upper limit of harvest index.
In 1840, Liebig of Germany discovered that the inorganic components required by plants are carbon dioxide, water, nitrogen, phosphorus, and potassium. Nitrogen, phosphorus and potassium could be supplied from the ore, but nitrogen (nitrate) was also a natural resource derived from feces of birds and was a material of explosive, so it was sometimes in short supply. A method to chemically fix nitrogen in the atmosphere was developed from the beginning of 1900, and in 1913 the German company BASF developed a technology to mass-production of nitrate industrially. The technology of nitrogen fixation also allowed the mass production of explosives, so it is considered to be one of reasons why Germany took the World War I. It became possible to perform nutritional supplementation by chemical fertilizer artificially that relied on soil microorganisms. After World War II, chemical fertilizer was produced in earnest. It was said that the gunpowder factory was turned into a chemical fertilizer factory one after another. In addition, herbicides and insecticides that kill and eliminate organisms other than crops were also put into farmland. These chemicals promoted grain growth and minimized wear damage.
When reclamation is done with civil engineering machines equipped with power and cultivation is done by machine, hard labor which had been dependent on the power of livestock and people until then has become unnecessary. In addition, construction of dams and agricultural canals by civil engineering machines make it possible that meadow or forest were used as cultivated land. Groundwater was also pumped up by the power plant and it became available as agricultural water.
Giving chemical fertilizer to new varieties that grain harvesting is large and is difficult to collapse, further reclaiming and cultivating using large machines, the world grain production amounted to 2-3 times in this half century. Together these three technologies are called green revolution.
As a result, food and living goods are overflowing around us today. However, on a global scale, conversely the increase in food production causes an increase in population, and food production is unlikely to catch up with population growth. Excessive use of water resources and cultivated areas simplifying complex ecosystems cause deterioration of the global environment and destruction of ecosystems.
Advanced countries have spread agriculture using chemical fertilizers and agricultural chemicals, and assembled developing countries into the world market. Developing countries prioritize the production of commodity crops such as coffee and cocoa to acquire foreign currency, and are forced to import grain for their life. In addition, traditional agricultural production is declining, a lot of farmers are produced with full of dissatisfaction with liabilities. The seeds of traditional edible plants are decreasing. Genetically modified crops (GMOs) are being alerted by developing countries as they strengthen agricultural and economic control by advanced countries.
Until the 18th century, scientific advances were hardly seen in medical technology. In the nineteenth century, great progresses have emerged in medical technology. One is safe surgery using anesthetic and disinfection technology, and the other is the development of vaccine.
As for anesthesia, there is a description saying that Hua Da, a doctor in the early 3rd century in later Han dynasty, performed general anesthesia using Mandarin (Korean morning gloria, thorn apple). The Mandarin contains chemical substances with strong sedative action called scopolamine. Since side effects are also strong, it was not used in general. Anesthesia as a medical technology was established in 1804 by Hanaoka Seishu in Kishu. He devised how to use Mandarin, improved efficacy and reduced side effects. Anesthetic effect of chloroform and ether was also found in the 19th century. It is easy to obtain because it can chemically be synthesized easily. However, the effect is not sustained, so it is necessary to control the amount of inhalation, side effects such as liver disorder. Nevertheless, the anesthesia method significantly reduces the patient's burden in surgical operations and raises the success rate of surgery.
Large injuries are often suppurative and fatal. For the treatment of suppuration, the affected part was incinerated with burning trowel to arrest bleeding and to prevent infection. After we understand the cause of suppuration is microbial breeding, in order to remove microorganisms as much as possible (disinfection), we wash hands before surgery and treat instruments and bandages with hot water. Also, chemicals to disinfect the wound have been devised, and the wound wrapped. The times of the discovery of pathogenic microorganisms was the same time as damage by battle of soldiers became worse, because large firearms such as cannons were used for war. The surgeons at battlefront decided to try the disinfection technique on the field to prevent suppuration of the wound.
Pasteur denied experimentally the theory of spontaneous microbial generation around 1860 and proved the presence of environmental microorganisms in air, water and soil. He thought that microorganisms cause rot and disease. In 1885, he developed a rabies vaccine. The idea that some diseases are caused by infection with microorganisms has become the basis for development of disinfection and sterilization methods. Many microbiologists have studied pathogenic bacteria causing gangrene, septicemia, puerperal fever and isolated as pathogenic bacteria. The first vaccine is smallpox vaccine (1796) by Jenner. The vaccine is a drug that makes animals resistant to infectious diseases, and surely confined epidemic infections. Especially in 1980, smallpox who was an enemy of human beings for many years was eradicated by the spread of vaccine.
In the 18th century, the number of dead in a war was those who died from infection overwhelmingly more than those from direct attack. The control of microorganisms by disinfection and sterilization enabled drastically to decrease the dead. In 1804, Mr. Appert invented canned and bottled food. The army adopted them as a portable food, then infectious diseases such as diarrhea drastically decreased. Still, the pandemic influenza epidemic in 1914 was raging in soldiers gathered for the World War I, and killed 20 million people worldwide.
Many drugs were discovered in the 20th century. Antipyretics, analgesics, anesthetics have advanced rapidly to be more effective and with few side effects. Using such as antibiotics, anesthesia and blood transfusion, surgeons can perform complicated surgical procedures such as cancer resection, heart surgery, or organ transplant. In particular, the power of antibiotics is enormous, dramatically improving the survival rate of newborns. Around 1950 when antibiotics were popularized, baby-boomer generation was formed in advanced countries, and distortion by age occurred in the population. In addition, antibiotic-resistant bacteria have been selected and have been shown to cause infections, especially in hospitals that use large amounts of antibiotics. The development of new antibiotics has not caught up with the emergence of resistant bacteria. Modern policies have been taken to effective use of as few antibiotics as possible.
When the control of microorganisms that killed a lot of people was almost completed, the next target of medical treatment became cancer and lifestyle diseases. While microorganisms are foreign enemies, cancer and lifestyle diseases can be said to be internal enemies. Human beings have changed their lifestyles to self-manage their bodies and spirits for healthy life. Due to progress in medicine, the culled genes in the past become preserved. A good example is myopia.
Race improvement has been done empirically from a long time ago. Plato envisioned a dictatorship elite society dominated by philosophers. He insisted that the ruler should secretly arrange a desirable male and female union. It should make a choice by lot. In Sparta, the newborn was interviewed by the tribal chief and frailty was abandoned deeply in the mountains. In the Roman times, people with malformations and incurable diseases were thrown away from the cliffs. Babies unwanted in the medieval Christian society were abandoned in public places, normal children were sometimes picked up, but children with disabilities were left alone. Since genetic analysis is possible in modern times, such screening is possible not only by phenotype but also by analysis of potential genes.
As a reference, modern epidemiological factors of high risk are reported by WHO in 2002. Low body weight, dangerous sexual intercourse, high blood pressure, tobacco, alcohol, dirt drinking water, hygienic hazard, high cholesterol, indoor smoke from solid fuel, iron deficiency, obesity, zinc deficiency, insufficient intake of vegetables, lack of exercise, Job injury risk, lead exposure, illegal drugs, infection with needles, not taking contraception, childhood sexual abuse.
In the 18th century, the Asian empires gave priority to stabilizing internal affairs against economic growth. On the other hand, the Europe countries began the political competition. The war between European countries has intensified by colonization of the African and the America where civilization was delayed. In addition, European countries has advanced to and promoted colonization of the Asia using the wealth gained on both continents. The European strengths that gained vast colonies led to the world wars.
Spain and Portugal were the first to win hegemony. Spain lost the naval battle with the UK and then declining. The UK got Africa, India and advanced further to the East. Meanwhile, the Netherlands and Belgium enhanced economic power with a focus on trade. France has advanced to North Africa, Russia and Austria robbed territories from Ottoman Turkey, whose power has declined. In addition, Russia acquired Siberia and advanced into the Sea of Okhotsk and Alaska.
Because the national state was established in France, it was attacked from the surrounding kingdom. Napoleon led the national army as a military, and removed their interferences, swept across Europe with its aggressive war as its mission. Other European countries had sense of crisis against the power of the national military. They also became national states one after another and had a national military.
On the other hand, the United States became independent from England. Then the countries of Latin America became independent. The United States issued the Monroe Declaration, completely denying the stereotype that the new continent (Americas) equals colonies by Europe.
Capitalism is fully dependent in expansion and growth. Capitalism at the national level was adopted by imperialism, and compete to gather colonies. It was inevitable that the world war brought about just before colonization of most of the world. Austria and Ottoman Turkey were divided into racial nations after the World War I, and the Russian revolution took place. Although the capitalist economy temporarily rallied due to the recovery from the World War I, the world economy and politics became confused by the 1929 World Depression. Among them, a totalitarian state (planned economy) such as the Soviet Union and the Nazis emerged. Fascism was inevitable where the national state system was extremely promoted. Nazi Germany, Japan Empire, Soviet Union developed a powerful military force. As a result, World War II broke out. Beginning with the tragedy of Guernica, an indiscriminate attack on the city was instantly started. In the nation-state regime, when the nation decides to war, the people must fight unlimitedly.
After the World War II, Europe was exhausted. The United States and the Soviet Union was established as the two major power system. The Soviet Union succeeded in industrialization by the planned economy which started from the World War I, and at the same time established a system of totalitarian communism. The influence of the Soviet Union dominated Eastern Europe, China and mainly the major parts of the Eurasian Continent. Meanwhile, the United States dominated global shipping by the mighty navy. The United States promoted the liberalization of trade by setting the disappearance of totalitarianism and colonialism as an international standard.
As a result of the two major powers being armed with nuclear missiles, direct confrontation became impossible. Two strong forces in the international community brought about waging war in each region. The Korean turbulence is its first, the Soviet invasion of Afghanistan is the last. Eventually, when the European society and Japan recovered their national strength, the Soviet regime became relatively weak and the economy of the Soviet Union began to stagnate. When the Communist party dictators became politically unstable, the Baltic States and Eastern Europe took a democratization campaign. Gorbachev accepted it, then the Soviet regime collapsed and the Cold War ended.
At the end of the Cold War, the civil war has intensified in the developing countries that had been stable due to the balance of the two powers. The United States, who confessed the world police, were also criticized by international society for the two Gulf Wars. When the demand by the Cold war disappeared, low-cost firearms were offered all over the world and the cost of war fell. Many local conflicts with army frequently occurred. Several countries are in ambiguity between normal time and wartime in various places. Moreover, the destruction activity by terrorism was activated in these countries with blank of power force. The symbol event was the September 11, 2001 terrorist incident in New York.
