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Jump to: ,

.

This timeline of the evolution of life outlines the major events in the development of on the planet (See ). For a thorough explanatory context, see the , and . The dates given in this article are estimates based on scientific evidence.

In , is the process by which populations of organisms acquire and pass on novel from generation to generation. Its occurrence over large stretches of time explains the origin of and ultimately the vast diversity of the biological world. Contemporary species are related to each other through , products of evolution and over billions of years.

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The basic timeline is a , with (very approximate) dates:

  • 4 billion years of , and first , and ,
  • 2.5 billion years of ,
  • 2 billion years of in ,
  • 1.4 billion years of ,
  • 1 billion years of ,
  • 550 million years of , , , , and ,
  • 475 million years of and proto-amphibians,
  • 418 million years of ,
  • 410 million years of ,
  • 372 million years of
  • 340 million years of ,
  • 220 million years of ,
  • 210 million years of ,
  • 160 million years of ,
  • 120 million years of ,
  • 65 million years since the non-avian ,
  • 60 million years of ,
  • 53 million years of ,
  • 52 million years of ,
  • 30 million years of ,
  • 6 million years of ,
  • 1 million years since the first fire made by our primate ancestors

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Note that , , means "million years ago".

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3800 Ma and earlier.

Date Event
4600 Ma The planet forms from the revolving around the young .
4533 Ma According to one plausible theory, the planet Earth and the planet collide, sending countless moonlets into orbit around the young Earth. These moonlets eventually coalesce to form the . The gravitational pull of the new Moon stabilises the Earth's fluctuating and sets up the conditions in which life formed.<ref> on the Giant Impact Hypothesis. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.</ref>
4100 Ma The surface of the Earth cools enough for the to solidify. The and the form.<ref>"However, once the Earth cooled sufficiently, sometime in the first 700 million years of its existence, clouds began to form in the atmosphere, and the Earth entered a new phase of development." (URL accessed on January 9, 2005)</ref> <ref>*</ref>, and synthesis along deep ocean platelet boundaries, may have led to the of competing organic compounds.
Between 4500 and 3500 Ma The appears, possibly derived from molecules.<ref></ref><ref></ref> The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with favouring those molecules which are more efficient at replication. molecules then take over as the main replicators and these archaic soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: .<ref name="Hoenigsberg2003SelectionWithoutSpeciation">(also available as )</ref><ref></ref><ref></ref>
3900 Ma : peak rate of upon the inner planets by meteors. This constant probably obliterated any life that had already evolved
Citation needed
, as the oceans boiled away completely; conversely, life may have been by a meteor.<ref>" Between about 3.8 billion and 4.5 billion years ago, no place in the solar system was safe from the huge arsenal of asteroids and comets left over from the formation of the planets. Sleep and Zahnle calculate that Earth was probably hit repeatedly by objects up to 500 kilometers across" (URL accessed on January 9, 2005)</ref>
Somewhere between 3900 - 2500 Ma resembling appear.<ref>, , "" , October 21, 1999.</ref> These first organisms are : they use as a source and inorganic materials to extract energy. Later, prokaryotes evolve , a set of chemical reactions that free the energy of organic molecules such as and store it in the chemical bonds of . Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.<ref>Romano AH, Conway T. (1996) Evolution of carbohydrate metabolic pathways. Res Microbiol. 147(6-7):448-55 </ref><ref></ref>

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3800 Ma – 2500 Ma

Date Event
3500 Ma Lifetime of the ;<ref>Doolittle, W. Ford (February, 2000). . Scientific American 282 (6): 90–95.</ref><ref>Nicolas Glansdorff, Ying Xu & Bernard Labedan: The Last Universal Common Ancestor : emergence, constitution and genetic legacy of an elusive forerunner. Biology Direct 2008, 3:29.</ref> the split between and occurs.<ref></ref>

Bacteria develop primitive forms of which at first do not produce .<ref></ref> These organisms generate by exploiting a , a mechanism still used in virtually all organisms.

3000 Ma Photosynthesizing evolve; they use water as a , thereby producing oxygen as waste product.<ref></ref> The oxygen initially oxidizes dissolved iron in the oceans, creating . The oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The is still very close to the earth and causes 1000 feet high. The earth is continually wracked by hurricane force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See )

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2500 Ma – 542 Ma

Date Event
By 2100 Ma cells appear.<ref>

</ref> Eukaryotes contain membrane-bound with diverse functions, probably derived from engulfing each other via . (See )

By 1200 Ma evolves, increasing the rate of evolution.<ref>"'Experiments with sex have been very hard to conduct,' Goddard said. 'In an experiment, one needs to hold all else constant, apart from the aspect of interest. This means that no higher organisms can be used, since they have to have sex to reproduce and therefore provide no asexual control.'
Goddard and colleagues instead turned to a single-celled organism, yeast, to test the idea that sex allows populations to adapt to new conditions more rapidly than asexual populations." (URL accessed on January 9, 2005)</ref>
1200 Ma Simple , mostly consisting of cell colonies of limited complexity.
850–630 Ma A may have occurred.<ref name=Hoffman1998> </ref><ref
name=Kirschvink1992></ref> Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution.<ref></ref><ref></ref><ref name=Corsetti2006>

</ref>

580–542 Ma The represent the first large, complex multicellular organisms - although their affinities remain a subject of debate.<ref></ref>
580–500 Ma Most modern of animals begin to appear in the fossil record during the .<ref name="BerkeleyCambrian"></ref><ref name="BristolUCEtiming"></ref>
580–540 Ma The accumulation of atmospheric oxygen allows the formation of an .<ref name="Formation of the Ozone Layer"></ref> This blocks radiation, permitting the colonisation of the land.<ref name="Formation of the Ozone Layer"/>

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542 Ma – present

The eon, literally the "period of well-displayed life", marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major .

era

542 Ma – 251.0 Ma

Date Event
530 Ma The first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of terrestrial plants.<ref>"The oldest fossils of footprints ever found on land hint that animals may have beaten plants out of the primordial seas. Lobster-sized, centipede-like or slug like animals such as and made the prints wading out of the ocean and scuttling over sand dunes about 530 million years ago. Previous fossils indicated that animals didn't take this step until 40 million years later." </ref>
434 Ma The first primitive move onto land,<ref>"The oldest fossils reveal evolution of non-vascular plants by the middle to late Ordovician Period (~450–440 Ma) on the basis of fossil spores" </ref>
Citation needed
having evolved from green algae living along the edges of lakes.<ref>"The land plants evolved from the algae, more specifically green algae, as suggested by certain common

biochemical traits" </ref> They are accompanied by , which may have aided the colonisation of land through .

363 Ma By the start of the period, the Earth begins to be recognisable. roamed the land and would soon take to the skies; swam the oceans as top predators,<ref>"The ancestry of sharks dates back more than 200 million years before the earliest known dinosaur. </ref> and vegetation covered the land, with seed-bearing plants and forests soon to flourish.

Four-limbed gradually gain adaptations which will help them occupy a terrestrial life-habit.

251.4 Ma The eliminates over 90-95% of marine species. Terrestrial organisms were not as seriously affected as the marine biota. This "clearing of the slate" may have led to an ensuing diversification.

era

Date Event
From 251.4 Ma The begins: increasingly well-adapted and diverse predators pressurise sessile marine groups; the "balance of power" in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
220 Ma
Eoraptor, among the earliest dinosaurs.
forests dominate the land; herbivores grow to huge sizes in order to accommodate the large guts necessary to digest the nutrient-poor plants.
Citation needed
200 Ma The first accepted evidence for (at least, the group ) exists.<ref>"Viruses of nearly all the major classes of organisms—animals, plants, fungi and bacteria/archaea—probably evolved with their hosts in the seas, given that most of the evolution of life on this planet has occurred there. This means that viruses also probably emerged from the waters with their different hosts, during the successive waves of colonisation of the terrestrial environment." (URL accessed on January 9, 2005)</ref> Viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon.
130 Ma The rise of the : These plants boast structures that attract insects and other animals to spread . This innovation causes a major burst of animal evolution through .

era

65.5 Ma – present

Date Event
65.5 Ma

The eradicates about half of all animal species, including all dinosaurs except the ancestors of <ref>. </ref>

35 Ma evolve from among the ; grassland dominates many terrestrial ecosystems.
200
(200,000 years ago)
appear in Africa.<ref> - URL retrieved May 15, 2009</ref><ref></ref><ref></ref> Around 50,000 years before present they start colonising the other continents, replacing the in Europe and other in Asia. The epoch starts 10,000<ref></ref> years ago after the , with continuing impact from human activity.
Present day With a approaching 6.8 billion,<ref>An estimate of the number of people alive on Earth at any given moment. </ref> the impact of humanity is felt in all corners of the globe. , climate change, , intensive agriculture, clearance of rain forests and other activities contribute to a dramatically rising extinction rate.<ref>The American Museum of Natural History (URL accessed on February 23, 2006)</ref> If current rates continue, humanity will have seen the eradication of one-half of Earth's biodiversity over the next hundred years.<ref>, Harvard University, The Future of Life (2002)</ref>

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  • by , for a list of ancestors common to humans and other living species

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  • - explore complete phylogenetic tree interactively
  • at the
  • from Planck Time to the lifespan of the universe
  • - from the University of Cambridge Ensemble Project
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