User:Arkuat/Preprehistory

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[edit] The short version of preprehistory

This is not really so short yet; as of 2008, I've just begun trying to condense it to a more manageable summary.

Began (-years) Name Events Duration (years)
-13.7 E9 Pregalactic Starts with the Big bang, and for this time is the chronology of the entire universe. (See Timeline of the Big Bang and Graphical timeline of the Big Bang.) Not long after the beginning of this period, helium nuclei (alpha particles) coalesce from free protons and neutrons. Later, electrons join with protons and alpha particles to form hydrogen and helium atoms, at which point space becomes transparent to light for the first time. Galaxies are currently thought to have begun forming around 600 million years after the Big bang, some 500 million years after the first star begins to shine. See reionization. 600 E6
-13 E9 Presolar Here we are talking about the chronology of our own galaxy, although it's no different in general from the chronology of the rest of the universe. 8e9 years of the history of the universe go by, during which all of the atoms in the Solar system (except H and He) form in stars and supernovae of the Milky Way galaxy. The first Population I stars are thought to have begun forming 10e9 years ago, some 4e9 years after the Big Bang. See also: Graphical timeline of the Stelliferous Era. 8000 E6
-4600 E6 Hadean Henceforth we are only discussing the chronology of a particular planetesy, and in particular of the planet Earth, which did not exist before this time. Solar nebula, Sun, and Solar system form at the beginning of this time. See Timetable of the Precambrian. Earth and Moon form from planetesimals. See in particular the animation at History of Earth#Moon. Ends after the Late Heavy Bombardment. 800 E6
-3800 E6 Archaean The calm between extraterrestrial bombardment and free oxygen. Reducing atmosphere supports the development of anaerobic prokaryotes (common ancestors of us and the Archea). Continents smaller than they are today because Earth's thermal heatflow three times higher than today. 1300 E6
-2500 E6 Proterozoic The Oxygen Catastrophe. Green bacteria (ancestors of chloroplasts as well as of contemporary green bacteria) produce free diatomic oxygen which floods the Earth's atmosphere and oceans. To the existing obligate anaerobes, oxygen is a potent toxin, and they retreat to something like their contemporary habitats. The ancestors of mitochondria and contemporary aerobic bacteria probably arose around this time as well. Evolution of sexual reproduction among protists? See Eukaryote#Origin and evolution. Initial Rodinian orogeny; expansion of platform covers. Pannotia forms and break up. Sturtian and Marinoan glaciations, AKA Snowball Earth, occur near the end of the Proterozoic. 1960 E6
-542 E6 Paleozoic The Phanerozoic eon begins. The great radiation of animal phyla probably happened during the late Proterozoic, but most of the fossil record of it was deposited during this time period. Trilobites are plentiful early on. Gondwana and Laurasia form. Early Paleozoic landscapes are purely rock, sand, clay, wind, and water: all macroscopic life is still confined to the ocean. Later, macroscopic plants and arthropods invade land, beginning to coevolve into great insect-infested forests (of tree-ferns), establishing what are now our seams of coal. Great radiation of bony fishes. First seed plants (gymnosperms and ancestors of angiosperms). Trilobites become rare later on. Giant amphibians and giant dragonflies succeed in the terrestrial forests. Appalachians and Urals form (see Alleghenian orogeny and Uralian orogeny). Toward the very end, we have one continent Pangaea and one ocean Panthalassa, and the first modern conifers. The Paleozoic ends with the most severe extinction event in the Earth's past. 291 E6
-251 E6 Mesozoic Gymnosperms and fern allies are dominant land plants. First flying vertebrates (pterosaurs). Pangaea endures as a single supercontinent. Massive volcanic eruptions (and extinctions) toward beginning of period as Pangaea begins to break up. Great radiation of dinosaurs. India begins to drift from Africa toward Asia, but other continents as now, although in different positions. Dinosaurs dominant. First adaptive radiation of birds. Extensive oceanic transgression. Great angiosperm radiation takes place, although land biomass is probably still dominated by gymnosperms up until the end of this period, the notorious Cretaceous-Tertiary extinction event. 185 E6
-65.5 E6 Cenozoic General cooling trend. Further radiation of angiosperms and birds. Great radiation of mammals. See below. 65 E6

[edit] A longer version of preprehistory

Began (-years) Name Events Duration (years)
-13.7 E9 Big bang Everything? See also: Graphical timeline of the Big Bang. 0
-13.7 E9 Preatomic Near the beginning of this period, helium nuclei (alpha particles) coalesce from free protons and neutrons. At the end of this period, electrons join with protons and alpha particles to form hydrogen and helium atoms, at which point space becomes transparent to light for the first time. 300 E3
-13.7 E9 Pregalactic Galaxies are currently thought to have begun forming around 600 million years after the Big bang, some 500 million years after the first star begins to shine. See reionization. 600 E6
-13 E9 Presolar 8e9 years of the history of the universe go by, during which all of the atoms in the Solar system (except H and He) form in stars and supernovae of the Milky Way galaxy. The first Population I stars are thought to have begun forming 10e9 years ago, some 4e9 years after the Big Bang. See also: Graphical timeline of the Stelliferous Era. 8000 E6
-4600 E6 Collapse of the presolar nebula Formation of the Solar nebula, Sun, and Solar system. See Timetable of the Precambrian. 100 E6
-4500 E6 Hadean Earth and Moon form from planetesimals at the beginning of this period. See in particular the animation at History of Earth#Moon. Ends after the Late Heavy Bombardment. 700 E6
-3800 E6 Archaean The calm between extraterrestrial bombardment and free oxygen. Reducing atmosphere supports the development of anaerobic prokaryotes (common ancestors of us and the Archea). Continents smaller than they are today because Earth's thermal heatflow three times higher than today. 1300 E6
-2500 E6 Paleoproterozoic The Oxygen Catastrophe. Green bacteria (ancestors of chloroplasts as well as of contemporary green bacteria) produce free diatomic oxygen which floods the Earth's atmosphere and oceans. To the existing obligate anaerobes, oxygen is a potent toxin, and they retreat to something like their contemporary habitats. The ancestors of mitochondria and contemporary aerobic bacteria probably arose around this time as well. The Paleoproterozoic era is the first of three eras of the Proterozoic eon. 900 E6
-1600 E6 Mesoproterozoic Evolution of sexual reproduction among protists? See Eukaryote#Origin and evolution. Initial Rodinian orogeny; expansion of platform covers. 700 E6
-900 E6 Neoproterozoic Algae and sponges and cnidaria, oh my. Rodinia and Pannotia form and break up. Sturtian and Marinoan glaciations, AKA Snowball Earth. 466 E6
-542 E6 Cambrian The Paleozoic era begins, and the Phanerozoic eon with it. The great radiation of animal phyla probably happened during the late Neoproterozoic, but most of the fossil record of it was deposited during this time period. 50 E6
-490 E6 Ordovician trilobites, brachiopods, (Taconic orogeny, Gondwana forms?) Ordovician landscapes are purely rock, sand, clay, wind, and water: all macroscopic life is still confined to the ocean. 50 E6
-443 E6 Silurian Plants and arthropods invade land, Laurasia starts to form 35 E6
-408 E6 Devonian First forests (of tree-ferns) appear. Plant/insect coevolution begins. Great radiation of bony fishes. 50 E6
-340 E6 Carboniferous Lignin-producing plants spread into vast forests. First seed plants (gymnosperms and ancestors of angiosperms). Trilobites become rare. Giant amphibians and giant dragonflies. Appalachians and Urals form (see Alleghenian orogeny and Uralian orogeny). 60 E6
-280 E6 Permian One continent Pangaea and one ocean Panthalassa. First modern conifers. The Permian (and the Paleozoic) ends with the most severe extinction event in the Earth's past. 29 E6
-245 E6 Triassic The Mesozoic era begins. Gymnosperms and fern allies are dominant land plants. First flying vertebrates (pterosaurs). Pangaea endures as a single supercontinent. Massive volcanic eruptions (and extinctions) toward end of period as Pangaea begins to break up. 46 E6
-200 E6 Jurassic Great radiation of dinosaurs. Modern continents begin to form. Nevadan orogeny. 60 E6
-135 E6 Cretaceous India still joined to Africa, but other continents as now, although in different positions. Dinosaurs dominant. First adaptive radiation of birds. Extensive oceanic transgression. Great angiosperm radiation takes place, although land biomass is probably still dominated by gymnosperms up until the end of this period, the notorious Cretaceous-Tertiary extinction event. 70 E6
-65.5 E6 Tertiary (i. e. Paleogene and almost all Neogene) The Cenozoic era (see below) begins. Great radiation of mammals and further reradiation of birds. Gradual cooling trend, retreat of shallow continental seas. Angiosperms become dominant land plants except in the taiga. 63 E6
-2 E6 Quaternary (i. e. very recent Neogene) See prehistory and history. 2 E6

[edit] A more detailed look at Cenozoic Earth

Began (-years) Epoch name Events Duration (years)
65.5e6 Paleocene The Tertiary and the Paleogene periods begin, simultaneously. Begins with ecological recovery from the great dying, with attendant radiation of mammals, birds, and angiosperms on land. Ends with a heat wave. 10e6
55.8e6 Eocene Exceptionally warm and homogeneous climate. Typical of the Paleogene period, in that it comprises the central half of it, the Eocene epoch was the warmest epoch of the Cenozoic. Throughout most of the Eocene, what we now think of as tropical forests grew up to very high latitudes (60 degrees or more) and mammals were generally smaller than in cooler epochs. The Azolla event produced by the warm climate is thought to have sequestered enough carbon to lead to our cooler climate today. Sirenians and cetaceans were developing during this epoch. The Indian subcontinent approached close enough to Eurasia to begin the Himalayan orogeny. 21e6
34.0e6 Oligocene South America separates from Antarctica and drifts north, allowing cool ocean circulation all the way around the continent and the development of the Antarctic ice cap as the epoch opened. The cool spell lasted throughout the entire epoch, the end of which is marked by the melting of the Antarctic ice again. The Paleogene ends at the same time the Oligocene epoch does. 11e6
23.0e6 Miocene The Neogene period begins, and the Miocene epoch comprises most of it and so may be said to be typical of the Neogene. The Miocene began with the melting of the Oligocene Antarctic icecap, but cooling trends continued, and the Antarctic icecap reformed from the late Miocene onward. Great radiation of grasses and ruminants as grasslands expand over territory formerly covered with forest. 18e6
5.33e6 Pliocene Australopithecines, mostly confined to this epoch, are completely bipedal. Antarctica remains icebound, as the Pliocene is cooler than the Miocene. The Pliocene is only one-fifth as long as the Miocene. The Tertiary period ends at the same time the Pliocene does (see Gelasian). 3.5e6
1.81e6 Pleistocene The Quarternary begins (see Gelasian). The Pleistocene epoch is known in archeology as the Paleolithic and is also known popularly as the Ice Ages. See Eemian interglacial for information about the last time (125,000 years ago) global climate was as warm as it is getting to be now. However, just as the Pliocene was cooler than the Miocene, the Pleistocene was cooler than the Pliocene. The Pleistocene is only half as long as the Pliocene, but encompasses almost all of human evolution since the australopithecine type. This epoch ends with the Younger Dryas. For general information see Timeline of glaciation. 1.8e6
0.012e6 Holocene The most recent interglacial period, running for 11,500 years so far. The Holocene is less than 1% the length of the Pleistocene. See Holocene extinction event, global warming, and prehistory and history. ongoing, 11.6e3 so far

[edit] See also