Timeline of the evolutionary history of life


This timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth. In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization, from kingdoms to species, and individual organisms and molecules, such as DNA and proteins. The similarities between all present day organisms indicate the presence of a common ancestor from which all known species, living and extinct, have diverged through the process of evolution. More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. However, a May 2016 scientific report estimates that 1 trillion species are currently on Earth, with only one-thousandth of one percent described.
While the dates given in this article are estimates based on scientific evidence, there has been controversy between more traditional views of increased biodiversity through a cone of diversity with the passing of time and the view that the basic pattern on Earth has been one of annihilation and diversification and that in certain past times, such as the Cambrian explosion, there was great diversity.

Extinction

Species go extinct constantly as environments change, as organisms compete for environmental niches, and as genetic mutation leads to the rise of new species from older ones. Occasionally biodiversity on Earth takes a hit in the form of a mass extinction in which the extinction rate is much higher than usual. A large extinction-event often represents an accumulation of smaller extinction- events that take place in a relatively brief period of time.
The first known mass extinction in earth's history was the Great Oxygenation Event 2.4 billion years ago. That event led to the loss of most of the planet's obligate anaerobes. Researchers have identified five major extinction events in earth's history since:
Smaller extinction-events have occurred in the periods between these larger catastrophes, with some standing at the delineation points of the periods and epochs recognized by scientists in geologic time. The Holocene extinction event is currently under way.
Factors in mass extinctions include continental drift, changes in atmospheric and marine chemistry, volcanism and other aspects of mountain formation, changes in glaciation, changes in sea level, and impact events.

Detailed timeline

In this timeline, Ma means "million years ago," ka means "thousand years ago," and ya means "years ago."

Hadean Eon

4000 Ma and earlier.
DateEvent
4600 MaThe planet Earth forms from the accretion disc revolving around the young Sun, with organic compounds necessary for life having perhaps formed in the protoplanetary disk of cosmic dust grains surrounding it before the formation of the Earth itself.
4500 MaAccording to the giant impact hypothesis, the Moon originated when the planet Earth and the hypothesized planet Theia collided, sending a very large number of moonlets into orbit around the young Earth which eventually coalesced to form the Moon. The gravitational pull of the new Moon stabilised the Earth's fluctuating axis of rotation and set up the conditions in which abiogenesis could occur.
4400 MaFirst appearance of liquid water on Earth.
4374 MaThe age of the oldest discovered zircon crystals.
4280 Ma Earliest possible appearance of life on Earth.

Archean Eon

4000 Ma - 2500 Ma
DateEvent
4000 MaFormation of a greenstone belt of the Acasta Gneiss of the Slave craton in Northwest Territories, Canada, the oldest rock belt in the world.
4100–3800 MaLate Heavy Bombardment : extended barrage of impact events upon the inner planets by meteoroids. Thermal flux from widespread hydrothermal activity during the LHB may have been conducive to abiogenesis and life's early diversification. "Remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia. This is when life most likely arose.
3900–2500 MaCells resembling prokaryotes appear. These first organisms are chemoautotrophs: they use carbon dioxide as a carbon source and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the energy of organic molecules such as glucose and store it in the chemical bonds of ATP. Glycolysis continue to be used in almost all organisms, unchanged, to this day.
3800 MaFormation of a greenstone belt of the Isua complex of the western Greenland region, whose rocks show an isotope frequency suggestive of the presence of life. The earliest evidences for life on Earth are 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada, graphite in 3.7 billion-year-old metasedimentary rocks discovered in western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia.
3500 MaLifetime of the last universal common ancestor ; the split between bacteria and archaea occurs.
Bacteria develop primitive forms of photosynthesis which at first did not produce oxygen. These organisms generated Adenosine triphosphate by exploiting a proton gradient, a mechanism still used in virtually all organisms.
3200 MaDiversification and expansion of acritarchs.
3000 MaPhotosynthesizing cyanobacteria evolved; they used water as a reducing agent, thereby producing oxygen as a waste product. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere slowly rose, acting as a poison for many bacteria and eventually triggering the Great Oxygenation Event. The Moon, still very close to Earth, caused tides high. The Earth was continually wracked by hurricane-force winds. These extreme mixing influences are thought to have stimulated evolutionary processes.
2800 MaOldest evidence for microbial life on land in the form of organic matter-rich paleosols, ephemeral ponds and alluvial sequences, some of them bearing microfossils.

Proterozoic Eon

2500 Ma - 542 Ma. Contains the Palaeoproterozoic, Mesoproterozoic and Neoproterozoic eras.
DateEvent
2500 MaGreat Oxidation Event led by cyanobacteria's oxygenic photosynthesis. Commencement of plate tectonics with old marine crust dense enough to subduct.
By 1850 MaEukaryotic cells appear. Eukaryotes contain membrane-bound organelles with diverse functions, probably derived from prokaryotes engulfing each other via phagocytosis.. Bacterial viruses emerge before, or soon after, the divergence of the prokaryotic and eukaryotic lineages. The appearance of red beds show that an oxidising atmosphere had been produced. Incentives now favoured the spread of eukaryotic life.
1400 MaGreat increase in stromatolite diversity.
1300 MaEarliest land fungi
By 1200 MaMeiosis and sexual reproduction are present in single-celled eukaryotes, and possibly in the common ancestor of all eukaryotes. Sex may even have arisen earlier in the RNA world. Sexual reproduction first appears in the fossil records; it may have increased the rate of evolution.
1000 MaThe first non-marine eukaryotes move onto land. They were photosynthetic and multicellular, indicating that plants evolved much earlier than originally thought.
750 MaFirst protozoa ; beginning of animal evolution
850-630 MaA global glaciation may have occurred. Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution. It is believed that this was due to evolution of the first land plants, which increased the amount of oxygen and lowered the amount of carbon dioxide in the atmosphere.
600 MaThe accumulation of atmospheric oxygen allows the formation of an ozone layer. Prior to this, land-based life would probably have required other chemicals to attenuate ultraviolet radiation enough to permit colonisation of the land.
580-542 MaThe Ediacara biota represent the first large, complex aquatic multicellular organisms — although their affinities remain a subject of debate.
580-500 MaMost modern phyla of animals begin to appear in the fossil record during the Cambrian explosion.
550 MaFirst fossil evidence for Ctenophora, Porifera, Anthozoa. Appearance of Ikaria wariootia.

Phanerozoic Eon

542 Ma - present
The Phanerozoic 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 mass extinctions.

Palaeozoic Era

542 Ma - 251.0 Ma and contains the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods.
s flourished during the early Paleozoic era, from the Late Cambrian, where they constituted the main predatory animals.
, a jawless fish, is popularized as one of the earliest fishes and probably a basal chordate or a basal craniate.
first appear in the fossil record about 360 million years ago in the late Devonian period.
DateEvent
535 MaMajor diversification of living things in the oceans: chordates, arthropods, echinoderms, molluscs, brachiopods, foraminifers and radiolarians, etc.
530 MaThe first known footprints on land date to 530 Ma.
525 MaEarliest graptolites
511 MaEarliest crustaceans
510 MaFirst cephalopods and chitons
505 MaFossilization of the Burgess Shale
500 MaJellyfish have existed since at least this time.
485 MaFirst vertebrates with true bones
450 MaFirst complete conodonts and echinoids appear
440 MaFirst agnathan fishes: Heterostraci, Galeaspida, and Pituriaspida
420 MaEarliest ray-finned fishes, trigonotarbid arachnids, and land scorpions
410 MaFirst signs of teeth in fish. Earliest Nautilida, lycophytes, and trimerophytes.
395 MaFirst lichens, stoneworts. Earliest harvestmen, mites, hexapods and ammonoids. The first known tetrapod tracks on land.
365 MaAcanthostega is one of the earliest vertebrates capable of walking.
363 MaBy the start of the Carboniferous Period, the Earth begins to resemble its present state. Insects roamed the land and would soon take to the skies; sharks swam the oceans as top predators, and vegetation covered the land, with seed-bearing plants and forests soon to flourish.
Four-limbed tetrapods gradually gain adaptations which will help them occupy a terrestrial life-habit.
360 MaFirst crabs and ferns. Land flora dominated by seed ferns. The Xinhang forest grows around this time
350 MaFirst large sharks, ratfishes, and hagfish
340 MaDiversification of amphibians
330 MaFirst amniote vertebrates
320 MaSynapsids separate from sauropsids in late Carboniferous.
305 MaEarliest diapsid reptiles
296 MaEarliest known octopus
280 MaEarliest beetles, seed plants and conifers diversify while lepidodendrids and sphenopsids decrease. Terrestrial temnospondyl amphibians and pelycosaurs diversify in species.
275 MaTherapsid synapsids separate from pelycosaur synapsids
270 MaGorgonopsians appear in the fossil record
251.4 MaThe Permian–Triassic extinction event 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, but life on land took 30 million years to completely recover.

Mesozoic Era

From 251.4 Ma to 66 Ma and containing the Triassic, Jurassic and Cretaceous periods.
DateEvent
250 MaThe Mesozoic Marine Revolution begins: increasingly well adapted and diverse predators pressurize sessile marine groups; the "balance of power" in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
250 MaTriadobatrachus massinoti is the earliest known frog
248 MaSturgeon and paddlefish first appear.
245 MaEarliest ichthyosaurs
240 MaIncrease in diversity of gomphodont cynodonts and rhynchosaurs
225 MaEarliest dinosaurs, first cardiid bivalves, diversity in cycads, bennettitaleans, and conifers. First teleost fishes. First mammals.
220 MaSeed-producing Gymnosperm forests dominate the land; herbivores grow to huge sizes to accommodate the large guts necessary to digest the nutrient-poor plants. First flies and turtles. First coelophysoid dinosaurs.
205
Ma		The Massive extinction of Triassic/Jurassic, that wiped out most of the group of pseudosuchians and gave the opportunity of dinosaurs including the Apatosaurus, Tyrannosaurus, Perrotasaurus, and Stegosaurus to enter their golden age.
200 MaThe first accepted evidence for viruses that infect eukaryotic cells existed. Viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon.
Major extinctions in terrestrial vertebrates and large amphibians. Earliest examples of armoured dinosaurs
195 MaFirst pterosaurs with specialized feeding. First sauropod dinosaurs. Diversification in small, ornithischian dinosaurs: heterodontosaurids, fabrosaurids, and scelidosaurids.
190 MaPliosauroids appear in the fossil record. First lepidopteran insects, hermit crabs, modern starfish, irregular echinoids, corbulid bivalves, and tubulipore bryozoans. Extensive development of sponge reefs.
176 MaFirst members of the Stegosauria group of dinosaurs
170 MaEarliest salamanders, newts, cryptoclidids, elasmosaurid plesiosaurs, and cladotherian mammals. Sauropod dinosaurs diversify.
165 MaFirst rays and glycymeridid bivalves. First vampire squids
163 MaPterodactyloid pterosaurs first appear
161 MaCeratopsian dinosaurs appear in the fossil record and the oldest known Eutherian Mammal appear in the fossil record: Juramaia.
160 MaMultituberculate mammals appear in eastern China
155 MaFirst blood-sucking insects, rudist bivalves, and cheilostome bryozoans. Archaeopteryx, a possible ancestor to the birds, appears in the fossil record, along with triconodontid and symmetrodont mammals. Diversity in stegosaurian and theropod dinosaurs.
153 MaFirst pine trees
140 MaOrb-weaver spiders appear
130 MaThe rise of the angiosperms: Some of these flowering plants bear structures that attract insects and other animals to spread pollen; other angiosperms were pollinated by wind or water. This innovation causes a major burst of animal evolution through coevolution. First freshwater pelomedusid turtles. Earliest krill.
120 MaOldest fossils of heterokonts, including both marine diatoms and silicoflagellates
115 MaFirst monotreme mammals
112 MaXiphactinus, a large predatory fish, appears in the fossil record
110 MaFirst hesperornithes, toothed diving birds. Earliest limopsid, verticordiid, and thyasirid bivalves.
106 MaSpinosaurus, the largest theropod dinosaur, appears in the fossil record
100 MaEarliest bees
95 MaFirst crocodilians evolve
90 MaExtinction of ichthyosaurs. Earliest snakes and nuculanid bivalves. Large diversification in angiosperms: magnoliids, rosids, hamamelidids, monocots, and ginger. Earliest examples of ticks. Probable origins of placental mammals.
80 MaFirst ants
70 MaMultituberculate mammals increase in diversity. First yoldiid bivalves.
68 MaTyrannosaurus, the largest terrestrial predator of what is now western North America appears in the fossil record. First species of Triceratops.

Cenozoic Era

66 Ma - present
from the American Museum of Natural History
appeared 52.2 million years ago
DateEvent
66 MaThe Cretaceous–Paleogene extinction event eradicates about half of all animal species, including mosasaurs, pterosaurs, plesiosaurs, ammonites, belemnites, rudist and inoceramid bivalves, most planktic foraminifers, and all of the dinosaurs excluding the birds.
66 Ma-Rapid dominance of conifers and ginkgos in high latitudes, along with mammals becoming the dominant species. First psammobiid bivalves. Earliest rodents. Rapid diversification in ants.
63 MaEvolution of the creodonts, an important group of meat-eating mammals
62 MaEvolution of the first penguins
60 MaDiversification of large, flightless birds. Earliest true primates, along with the first semelid bivalves, edentate, carnivoran and lipotyphlan mammals, and owls. The ancestors of the carnivorous mammals were alive.
59 MaEarliest sailfish appear
56 MaGastornis, a large flightless bird, appears in the fossil record
55 MaModern bird groups diversify, first whale, earliest lagomorphs, armadillos, appearance of sirenian, proboscidean, perissodactyl and artiodactyl mammals in the fossil record. Angiosperms diversify. The ancestor of the species in the genus Carcharodon, the early mako shark Isurus hastalis, is alive.
52 MaFirst bats appear
50 MaPeak diversity of dinoflagellates and nannofossils, increase in diversity of anomalodesmatan and heteroconch bivalves, brontotheres, tapirs, rhinoceroses, and camels appear in the fossil record, diversification of primates
40 MaModern-type butterflies and moths appear. Extinction of Gastornis. Basilosaurus, one of the first of the giant whales, appeared in the fossil record.
38 MaEarliest bears
37 MaFirst nimravid carnivores — these species are unrelated to modern-type felines. First alligators
35 MaGrasses diversify from among the monocot angiosperms; grasslands begin to expand. Slight increase in diversity of cold-tolerant ostracods and foraminifers, along with major extinctions of gastropods, reptiles, amphibians, and multituberculate mammals. Many modern mammal groups begin to appear: first glyptodonts, ground sloths, canids, peccaries, and the first eagles and hawks. Diversity in toothed and baleen whales.
33 MaEvolution of the thylacinid marsupials
30 MaFirst balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats
28 MaParaceratherium appears in the fossil record, the largest terrestrial mammal that ever lived. First pelicans.
25 MaPelagornis sandersi appears in the fossil record, the largest flying bird that ever lived
25 MaFirst deer
24 MaFirst pinnipeds
23 MaEarliest ostriches, trees representative of most major groups of oaks have appeared by now
20 MaFirst giraffes, hyenas, and giant anteaters, increase in bird diversity
17 MaFirst birds of the genus Corvus
15 MaGenus Mammut appears in the fossil record, first bovids and kangaroos, diversity in Australian megafauna
10 MaGrasslands and savannas are established, diversity in insects, especially ants and termites, horses increase in body size and develop high-crowned teeth, major diversification in grassland mammals and snakes
9.5 Ma The Great American Interchange, where various land and freshwater faunas migrated between North and South America. Armadillos, opossums, hummingbirds Phorusrhacids, Ground Sloths, Glyptodonts, and Meridiungulates traveled to North America, while horses, tapirs, saber-toothed cats, Jaguars, Bears, Coaties, Ferrets, Otters, Skunks and deer entered South America.
9 MaFirst platypuses
6.5 MaFirst hominins
6 MaAustralopithecines diversify
5 MaFirst tree sloths and hippopotami, diversification of grazing herbivores like zebras and elephants, large carnivorous mammals like lions and the genus Canis, burrowing rodents, kangaroos, birds, and small carnivores, vultures increase in size, decrease in the number of perissodactyl mammals. Extinction of nimravid carnivores. First leopard seals.
4.8 MaMammoths appear in the fossil record
4.5 MaMarine iguanas diverge from land iguanas
4 MaEvolution of Australopithecus, Stupendemys appears in the fossil record as the largest freshwater turtle, first modern elephants, giraffes, zebras, lions, rhinoceros and gazelles appear in the fossil record
3.6 MaBlue whales grow to their modern sizes
3 MaEarliest swordfish
2.7 MaEvolution of Paranthropus
2.5 MaThe earliest species of Smilodon evolve
2 MaFirst members of the genus Homo, Homo Habilis, appear in the fossil record. Diversification of conifers in high latitudes. The eventual ancestor of cattle, aurochs, evolves in India.
1.7 MaExtinction of australopithecines
1.2 MaEvolution of Homo antecessor. The last members of Paranthropus die out.
1 MaFirst coyotes
800 KaShort-faced bears become abundant in North America
600 kaEvolution of Homo heidelbergensis
400 kaFirst polar bears
350 kaEvolution of Neanderthals
300 kaGigantopithecus, a giant relative of the orangutan from Asia dies out
250 kaAnatomically modern humans appear in Africa. Around 50,000 years before present they start colonising the other continents, replacing the Neanderthals in Europe and other hominins in Asia.
40 kaThe last of the giant monitor lizards die out
30 kaExtinction of Neanderthals, first domestic dogs
15 kaThe last woolly rhinoceros are believed to have gone extinct
11 kaShort-faced bears vanish from North America, with the last giant ground sloths dying out. All Equidae become extinct in North America.
10 kaThe Holocene epoch starts 10,000 years ago after the Late Glacial Maximum. The last mainland species of woolly mammoth die out, as does the last Smilodon species.
8 kaThe Giant Lemur died out
Historical extinctions
DateEvent
6000 ya Small populations of American mastodon die off in places like Utah and Michigan
4500 ya The last members of a dwarf race of woolly mammoths vanish from Wrangel Island near Alaska
c. 600 ya The moa and its predator, Haast's eagle, die out in New Zealand
ya The last recorded wild aurochs die out
ya The dodo goes extinct
ya The Steller's sea cow goes extinct
ya The quagga, a subspecies of zebra, goes extinct
114 ya Wolves become extinct in Japan.
ya Martha, last known passenger pigeon, dies
ya The thylacine goes extinct in a Tasmanian zoo, the last member of the family Thylacinidae
82 ya The last Bali tiger was shot.
ya The Caribbean monk seal goes extinct
ya The baiji, the Yangtze river dolphin, becomes functionally extinct, according to the IUCN Red List
ya The western black rhinoceros is declared extinct