Timeline of evolution

From Wikipedia, the free encyclopedia

For the history of evolutionary biology, see History of evolutionary thought.

This timeline of the evolution of life outlines the major events in the development of life on the planet Earth. For context, see geologic time scale, and the history of Earth. Dates given are estimates based on scientific evidence. The table uses the symbols "Ma" for "mega-annum (million years ago)" and "ka" for "kilo-annum (thousand years ago)". English literature also uses the abbreviations "mya" (m.y.a) and "tya" (t.y.a) or "kya" in the same sense.

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

The basic timeline is a 4600 million year old Earth, with

For a list of our common ancestors with other living species, see The Ancestor's Tale.

Date Event
4600 Ma The planet Earth forms from the accretion disc revolving around the young Sun.
4533 Ma The planet Earth and the planet Theia collide, causing rings to form around the young Earth which last for millions of years until they coalesce to form the Moon, the gravitational pull of which stabilises the Earth's fluctuating axis of rotation, setting up the conditions for the formation of life.[1]
4100 Ma The surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form.[2]
4000 Ma The earliest life appears, possibly derived from self-reproducing RNA molecules. The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition. Natural selection favors those molecules which are more efficient at replication. DNA molecules then take over as the main replicators. They soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells. At this time, the atmosphere does not contain any free oxygen.
3900 Ma Late Heavy Bombardment: peak rate of impact events upon the Earth, Moon, Mars and Venus by asteroids and comets (planetesimals). This constant disturbance may encourage life to evolve (see panspermia). It is thought that these impacts cause the oceans to boil away completely, more than once; yet life persists.[3]

Cells 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. Glycolysis generates ATP molecules as short-term energy currency, and ATP continue to be used in almost all organisms, unchanged, to this day.
3500 Ma Lifetime of the last universal ancestor; the split between the bacteria and the archaea occurs.

Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen. These organisms generate ATP by exploiting a proton gradient, a mechanism still used in virtually all organisms.
3000 Ma
Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The moon is still very close to the earth and causes tides 1000 feet high. The earth is continually wracked by hurricane force winds. These extreme mixing influences are thought to stimulate evolutionary processes.[citation needed]
2500 Ma Some bacteria evolve the ability to utilize oxygen to more efficiently use the energy from organic molecules such as glucose. Virtually all organisms using oxygen employ the same set of reactions, the citric acid cycle and oxidative phosphorylation.

The "runaway icehouse" effect[4] results in the Huronian glaciation (2500–2100 Ma).[5]
2100 Ma More complex cells appear: the eukaryotes, the closest relatives of whom are probably the archaea. Eukaryotes contain various organelles with diverse functions, probably derived from the co-evolution of symbiotic communities of prokaryotes. The most dramatic examples are mitochondria, which use oxygen to extract energy from organic molecules and appear similar to today's Rickettsia. Many eukaryotes also have chloroplasts, organelles which originated from cyanobacteria and similar organisms, which derive energy from light and synthesize organic molecules.
1200 Ma Sexual reproduction evolves, leading to faster evolution.[6] While most life still exists in oceans and lakes, some cyanobacteria may already live in moist soil by this time.
1000 Ma Multicellular organisms appear: initially colonial algae, and later seaweeds, living in the oceans.[7]
900 Ma
The choanoflagellates develop. These protists are considered the ancestors of the entire animal kingdom, and specifically the direct ancestors of the sponges: the choanocytes ("collar cells") of sponges (and a few other animal groups, such as flatworms) have the same basic structure as choanoflagellates, and DNA evidence suggests a close relationship between the two.

The modern species proterospongia, consisting of choanoflagellates that live in colonies and exhibit primitive cell specialization for different tasks, is likely very similar to the ancient ancestor species that would have bridged the gap between choanoflagellates and sponges, and thereby between protozoa and all metazoa (multicellular animals).
1000–750 Ma The first known supercontinent, Rodinia, forms, and then breaks apart again.
950–780 Ma Sturtian ice age, a time of multiple near-global glaciations, with periods oscillating between a Snowball Earth and a greenhouse Earth.
900 Ma There are 481 18-hour days in a year. The rotation of the Earth has gradually slowed ever since.
750–580 Ma According to the Snowball Earth hypothesis, the Precambrian Varangian ice age is so severe that the Earth's oceans freeze over completely; only in the tropics do oceans remain liquid. This is the last big freeze, and afterwards, evolution begins to accelerate.
600 Ma
Sponges (Porifera), the earliest multicellular animals, develop from cell colonies. Sponges are the simplest and most primitive animals, having partially-differentiated tissues but no muscles, nerves, internal organs, or capacity for locomotion.

Following sponges, Cnidaria (jellyfish, etc.), Ctenophora, and other multicellular animals appear in the oceans. Cnidaria and Ctenophora are some of the earliest creatures to have neurons, in the form of a simple net, with no central nervous system. They possess muscular tissue and digestive systems with mouths. Unlike sponges, these animals have structured bodies with organs and radial symmetry.

Flatworms (Platyhelminthes), the earliest animals to have a rudimentary brain and the simplest animals with bilateral symmetry, develop. They are also the simplest animals to have organs that form from three germ layers (triploblasty). There are still no organisms with a true circulatory or respiratory system.

The Ozone layer forms, allowing for the first major excursions onto the land. The second supercontinent, Pannotia, forms, then breaks up by 540 Ma.
542–530 Ma
The Cambrian explosion, a rapid set of evolutionary changes, creates all the major body plans (phyla) of modern animals. The cause of this huge expansion in the variety of life forms is still a matter of scientific debate. Arthropoda, represented by an abundance of trilobites, is the dominant phylum. Anomalocaris is a predator up to 2 meters in length.[8]

The worm-like organisms develop more highly specialized and advanced structures, such as the circulatory system of acorn worms, which features a heart that also functions as a kidney. Acorn worms have a gill-like structure, similar to that of primitive fish, used for breathing. Acorn worms are thus sometimes said to be a link between vertebrates and invertebrates.

Pikaia, a small swimmer and the earliest-known animal with a notochord, is believed to be the ancestor of all chordates and vertebrates. The lancelet, a species still alive today, retains some of the features of the primitive chordates, and resembles the Pikaia in many ways. The conodont is an "eel-shaped animal of 4–20 cm long" with a pair of huge eyes and a complex basket of teeth.

The first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of terrestrial plants.[9]
505 Ma
The first vertebrates appear: the ostracoderms, jawless fish (Agnatha) such as Haikouichthys and Myllokunmingia. They have cartilaginous internal skeletons, and lack the paired (pectoral and pelvic) fins of more advanced prehistoric fish. They are precusors of the Osteichthyes (bony fish), and are related to present-day lampreys and hagfishes.
488 Ma
The first of the seven major extinction events over geological time occurs at the Cambrian-Ordovician transition.

Soon after, the first of the jawed fishes, Placodermi, develop. Their jaws evolve from the first of their gill arches.[10] Their head and thorax are covered by articulated armored plates, while the rest of the body is scaled or naked.
475 Ma The first primitive plants move onto land,[11] having evolved from green algae living along the edges of lakes.[12] They are accompanied by fungi, and very likely plants and fungi work symbiotically together; lichens exemplify such a symbiosis.
450 Ma
Centipede
Arthropods, with an exoskeleton that provides support and prevents water loss,[13] are the first animals to move onto land.[14] Among the first are Myriapoda (millipedes and centipedes), later followed by spiders and scorpions.

Over the next ten million years, the two Ordovician-Silurian extinction events occur. Taken together, these constitute the second mass extinction event.
400 Ma The first insects evolve, the wingless silverfish, springtails (no longer considered insects), and bristletails. First sharks appear.[15] First Coelacanth appears; this order of animals had been thought to have no extant members, until living specimens were discovered in 1938. It is often referred to as a living fossil.
375 Ma Tiktaalik is a genus of sarcopterygian (lobe-finned) fishes from the late Devonian with many tetrapod-like features.
370 Ma Cladoselache, a shark, is a high-speed predator.[16]
365 Ma The Late Devonian extinction is the third mass extinction.

New insect species evolve on land and in fresh water from the myriapods.

Some lobe-finned fish (Sarcopterygii) develop legs and give rise to early four-limbed tetrapods: Ichthyostega, Acanthostega and Pederpes finneyae. Initially aquatic, dwelling in shallow, swampy freshwater habitats, these fishes use their fins as paddles to assist in navigating shallow waters choked with plants and detritus—the likely origin of front limbs bending backward at the elbow and hind limbs bending forward at the knee. Eventually, these tetrapods use their rudimentary legs to move out onto land for brief periods, probably to hunt insects. Lungs and swim bladders evolve.

Primitive tetrapods developed from a fish with a two-lobed brain in a flattened skull, a wide mouth, and a short snout, whose upward-facing eyes show that it was a bottom-dweller, and which had already developed adaptations of fins with fleshy bases and bones. The "living fossil" coelacanth is a related lobe-finned fish without these shallow-water adaptations. Amphibians today still retain many characteristics of the early tetrapods.
360 Ma Plants evolve seeds, structures that protect plant embryos and enable plants to spread quickly on land.

Creation of Woodleigh crater (100 km wide) and Siljan Ring (40 km wide, Dalecarlia, Sweden).
360–286 Ma The golden age of sharks[17].
350-250 Ma The Karoo Ice Age begins in the early Carboniferous and ends in the Permian. Advancing ice sheets in Gondwanaland are at first centered in Africa and South America, and later in India and Australia, due to polar wandering.
300 Ma The supercontinent Pangea forms and will last for 120 million years; this is the last time all of the earth's continents fuse into one. Evolution of the amniotic egg gives rise to the Amniota, reptiles, who can reproduce on land. Insects evolve flight, and include a number of different orders (e.g. Palaeodictyoptera, Megasecoptera, Diaphanopterodea, and Protorthoptera) Dragonflies (Odonata) still resemble many of these early insects. Vast forests of clubmosses (lycopods), horsetails, and tree ferns cover the land; when these decay they will eventually form coal and oil. Gymnosperms begin to diversify widely. Cycads, plants resembling palms, first appear.
280 Ma The Protodonatan dragonfly Meganeura monyi is among the biggest insects that ever lived, with a wingspan of about 2 feet. Vertebrates include many Temnospondyl, Anthrachosaur, and Lepospondyl amphibians and early anapsid and synapsid (e.g. Edaphosaurus) reptiles.
256 Ma Diictodon, Cistecephalus, Dicynodon, Lycaenops, Dinogorgon and Procynosuchus, are a few of the many mammal-like reptiles known from South Africa and Russia. Pareiasaurs were large clumsy herbivores. The first Archosauriformes.
250 Ma The Permian-Triassic extinction event wipes out about 90% of all animal species; this fourth extinction event is the most severe mass extinction known.

Lystrosaurus is a common herbivore that survives the extinction event. The archosaurs split from other reptiles. Teleosts evolve from among the Actinopterygii (ray-finned fish), and eventually become the dominant fish group. Atmospheric oxygen, at 10%, is one third of its former level, so animals with air sac breathing systems will do well (present-day bird respiration exemplifies the air sac system). Some spores of bacteria Bacillus strain 2-9-3 (Sali bacillus marismortui) are trapped in salt crystals known as halite in New Mexico. They are re-animated in AD 2000 and have multiplied rapidly. Currently the world oldest living organism. [18]
220 Ma The climate is very dry, and dry-adapted organisms are favored: the archosaurs and the Gymnosperms. Archosaurs diversify into crocodilians, dinosaurs, and pterosaurs.

From synapsids come the first mammal precursors, therapsids, and more specifically the eucynodonts. Initially, they stay small and shrew-like. All mammals have milk glands for their young, and they keep a constant body temperature. Also, one of a pair of autosomes acquires gene SRY (derived from the SOX3 gene of the X chromosome) to become the Y chromosome, which has been decreasing in length since. Gymnosperms (mostly conifers) are the dominant land plants. Plant eaters will grow to huge sizes during the dominance of the gymnosperms to have space for large guts to digest the poor food offered by gymnosperms.
208-144 Ma Second major spread of sharks[19].
200 Ma Fifth mass extinction event occurs at the Triassic-Jurassic transition.

Marine reptiles include Ichthyosaurs and Plesiosaurs. Ammonites and belemnites flourish. Dinosaurs survive the extinction and grow to large size, but the thecodonts, or "socket-toothed" reptiles, die out. Modern amphibians evolve: the Lissamphibia; including Anura (frogs), Urodela (salamanders), and Caecilia. Geminiviridae, a diverse group of viruses, are traceable to this epoch or earlier[20].
180 Ma The supercontinent Pangea begins to break up into several land masses. The largest is Gondwana, made up of the land masses which are now Antarctica, Australia, South America, Africa, and India. Antarctica is still a land of forests. North America and Eurasia are still joined, forming the Northern supercontinent, Laurasia. Speciation occurs due to the water barriers created by the breakup.
164 Ma The oldest swimming mammal, Castorocauda lutrasimilis, is the immediate predecessor of modern mammals such as the platypus and echidna.
160 Ma 3 metres long, Guanlong wucaii - meaning crested dragon from the five colours, Xinjiang province in northwestern China, is the oldest Tyrannosaur.
150 Ma Giant dinosaurs are common and diverse - Brachiosaurus, Apatosaurus, Stegosaurus, Allosaurus, along with smaller forms like Ornitholestes and Othneilia. Birds evolve from theropod dinosaurs. Archaeopteryx is an ancestor of birds, with claws, feathers but no beak.
135 Ma New dinosaurs Iguanodon, Hylaeosaurus, etc., appear after extinction of Jurassic forms. Microraptor gui, a 77 cm long dinosaur in Liaoning, Northeast China, has bird-like feathered wings on 4 limbs.
133 Ma Shenzhouraptor sinensis, a primitive bird found in the Yixian Formation of north-eastern China, eats seeds. The bird has large, strong wings, and also had a long, bony tail, like many dinosaurs.
130 Ma Angiosperm plants evolve flowers, structures that attract insects and other animals to spread pollen. This innovation of the angiosperms causes a major burst of animal evolution and co-evolution.
128 Ma One early tyrannosaur is Dilong paradoxus in Lioning Province of China. Has feathers and a small body of 5 feet (1.5 m) long.
125 Ma Eomaia scansoria, a eutherian mammal, which leads to the formation of modern placental mammals. It looks like a modern dormouse, climbing small shrubs in Liaoning, China. The parrot-beaked Psittacosaurus is the ancestor of the later horned dinosaurs.
123 Ma

Sinornithosaurus millenii is a dinosaur in Liaoning, China that has primitive feathers not used for flight. Other dinosaurs with feathers are Sinosauropteryx (most primitive feathers, simplest tubular structures) and Changchanornis. Other dinosaurs include Polacanthus (armoured herbivore) and Eotyrannus (early tyrannosaur). Evolution of birds has gone underway, with several different lineages existing (e.g. Confuciusornis and 'Yanornis).
110 Ma Sarcosuchus imperator, eight metric tons, 12 m long, head 2 m long, largest crocodile. Carnivorous dinosaurs included the "raptor" Deinonychus and sail-backed semi-aquatic spinosaurs, herbivores include the tallest known sauropod Sauroposeidon proteles, as well as the bulbous-nosed iguanodont Altirhinus (ancestral to duck-bills) and the armoured Sauropelta. Gansus yumenensis, the earliest known essentially modern bird, lives in today's China.
100 Ma The giant theropod dinosaurs Carcharodontosaurus and Giganotosaurus are even bigger than Tyrannosaurus.
88 Ma Breakup of Indo-Malagasy land mass.
80 Ma Many kinds of sauropod, duck billed, horned and meat-eating dinosaurs; half of all known dinosaur species are from the last 30 MY of the Mesozoic, after the rise of the angiosperms. India starts moving to Eurasia.
75 Ma Oviraptor was one of the most bird-like of the non-avian dinosaurs. Last common ancestor of humans and mice [21]. The Hesperornithes and Ichthyornithes, extinct birds with teeth, roamed the oceans of the Northern Hemisphere.
67 Ma Vegavis iaai, the oldest known bird assignable to a group still extant today, lives on the shores of Antarctica. It is a presbyornithid, a kind of wading goose.
65 Ma The Cretaceous-Tertiary extinction event (sixth extinction event) wipes out about half of all animal species including all non-avian dinosaurs, probably because of a cooling of the climate precipitated by the giant impact of an asteroid: iridium powder from the asteroid forms a layer that covers the whole Earth. Creation of the Chicxulub Crater (170 km across, now half-submerged off the Yucatan peninsula of Mexico).

Without the presence of the giant and diurnal dinosaurs, mammals can increase in diversity and size. Some will later return back to the sea (whales, sirenians, seals) and others will evolve flight (bats). A group of small, nocturnal and arboreal, insect-eating mammals called the Archonta branches into what will be the primates, treeshrews, and bats. Primates have binocular vision and grasping digits, features that help them to jump from one tree branch to another. One example of a proto-primate is Plesiadapis which is extinct by 45 million years ago. Except the Neornithes lineage which exists today, all birds become extinct in the catastrophe.
60 Ma Creodont, meat eater, northern hemisphere, extinct by 5.2 million years ago, possible ancestor of Miacids.
55 Ma Australia breaks away from Antarctica. Proto-primates first appear in North America, Asia, and Europe. One example is Carpolestes simpsoni at Clarks Fork Basin of Wyoming. It has grasping digits but no forward facing eyes. Another (earliest?) euprimate Teilhardina asiatica (Hunan, China) is mouse-sized, diurnal, and has small eyes. An ancestor of the Shortfin mako shark probably gives rise to the lineage of the Great White Shark, but not the Megalodon [22].
50 Ma

The evolution of the horse starts with Hyracotherium: the size of a fox with large nails instead of hoofs. Ancestor of whales (which include dolphins), Ambulocetus natans (Pakistan) probably walks on land like the modern sea lion and swims like modern otters. It has webbed feet that give it added power when swimming, and still hears directly from its ears. Pezosiren portelli, ancestor of modern manatees, walks like a hippo and swims like an otter. Miacids include Miacis, a five-clawed ancestor of all dogs, cats, bears, raccoon, fox, hyena, jackal, civet; it is a meat-eating, weasel-like tree climber.
48.5 Ma Gastornis geiselensis (Europe, USA), a carnivorous bird 1.75 m tall, is a top predator
46.5 Ma Rodhocetus, ancestor of whale, successor to Ambulocetus, no longer needs to drink fresh water.
43 Ma Earliest elephant, Moeritherium (Egypt): 1m tall, size of a large pig, eats soft, juicy plants. It has a long nose, but no trunk nor tusks.
40 Ma Primates (order) diverge into suborders Strepsirrhini (lemurs and lorises) and Haplorrhini (tarsiers, monkeys and apes); the latter is diurnal and herbivorous.
37 Ma

Basilosaurus, up to 20 m long, snakelike ancestor of whales, has reduced but well-developed hind limbs. Hears from sounds transmitted to middle ears through vibrations from lower jaws. In Egypt's 'Whale Valley', what would later be the Wadi Hitan desert is underwater, teeming with Basilosaurus isis which had no blowhole but had to raise its head above water to breathe. Early ancestors of strepsirrhines primate appear in the Egyptian desert, Biretia fayumensis and Biretia megalopsis.[23].
35 Ma Grasses evolve from among the angiosperms.
34 Ma Cynodictis, or dawn dog, appears in North America. Canids will eventually colonize the world.
30 Ma Haplorrhini (suborder) splits into infraorders Platyrrhini (New World monkeys) and Catarrhini (Old World primates). New World monkeys have prehensile tails and migrate to South America. Catarrhines stay in Africa as the two continents drift apart. One ancestor of catarrhines might be Aegyptopithecus. New World monkey males are color blind. Haplorrhines: Bugtipithecus inexpectans, Phileosimias kamali and Phileosimias brahuiorum, similar to today's lemurs, live in rainforests on Bugti Hills of central Pakistan. Ancestor of all cats, 9 kg Proailurus, lives in trees in Europe, goes extinct 20 million years ago.
27.5 Ma Indricothere, rhino relative, 4.5 m tall, tallest mammal on land, lives in Mongolia.
27 Ma The Phorusrhacidae ("Terror birds"), up to 2.5 m tall, are among the top-level carnivores in the Americas. They went extinct only 2 million years ago.
25 Ma Catarrhini males gain color vision but lose the pheromone pathway [24]. Catarrhini splits into 2 superfamilies, Old World monkeys (Cercopithecoidea) and apes (Hominoidea). The Old World primates do not have prehensile tails (e.g. Baboon); some do not have tails at all. All hominoids are without tails.
22 Ma India collides with Asia, causing the rise of Himalaya and the Tibetan plateau. Cut off from the humidity, Central Asia becomes a desert. Appearance of deinotherium, ancient elephant, extinct by 2 million years ago. Evolving from an animal that looks part dog, part bear and part raccoon, the dawn bear (Ursavus elmensis) is the ancestor of all bears living today. It is the size of a fox, hunts in the tree tops, and supplements a diet of meat with plant material and insects. The first group, the Ailuropodinae, follows a plant-based diet, branches off, and only one member, the giant panda (Ailuropoda melanoleuca), survives today.
21 Ma A mongoose-like creature floats to Madagascar from Africa on a raft of vegetation. It becomes the ancestor of all carnivorous mammals there.[citation needed]
20 Ma The African plate collides with Asia. Cynodictis, ancestor of dogs, has a shortened fifth claw which foreshadows the dewclaw (vestigial) of modern dogs. They look like the modern day civet and have feet and toes suited for running. The two superfamilies of carnivores (canines and felines) are distinct by this time. Gomphotherium, ancient elephant.
19 Ma Megatherium americanum (giant sloth, 6m long, extinct 8000 years ago) and Argentavis magnificens (the largest bird ever to fly, wingspan some 7 meters or more) are among the gigantic animals that roam South America.
16 Ma Squalodon shows early echolocation of whales. Megalodon is a gigantic shark the size of a bus [25]; it has a long reign and disappears suddenly about 1.6 Ma.
15 Ma Apes from Africa migrate to Eurasia to become gibbons (lesser apes) and orangutans. Human ancestors speciate from the ancestors of the gibbon. Orangutans, gorillas and chimpanzees are great apes. Humans are hominins.
13 Ma Human ancestors speciate from the ancestors of the orangutan. A relative of orangutans: Lufengpithecus chiangmuanensis (Northern Thailand). Pierolapithecus catalaunicus, Spain, possibly common ancestor of great apes and humans.
10 Ma The climate begins to dry; savannas and grasslands take over the forests. Monkeys proliferate, and the apes go into decline. Human ancestors speciate from the ancestors of the gorillas. This is the heyday of the horses as they spread throughout the Northern hemisphere. After 10 Ma they decline in the face of competition from the artiodactyls. Tomarctus, ancestor of dogs, is an extremely dog like animal.
7 Ma Biggest primate Gigantopithecus is 2 m tall and lives in China (Gigantopithecus blacki), Vietnam, and northern India (Gigantopithecus bilaspurensis). Extinct by 300,000 years ago.
5.6 Ma Drying up of the Mediterranean Sea (the Messinian Event).
5 Ma Volcanoes erupt and create the small area of land that joins North and South America. Mammals from North America move South and cause extinction of mammals there.

Human ancestors speciate from the ancestors of the chimpanzees. The latest common ancestor is Sahelanthropus tchadensis (Chad, Sahara, west of Rift Valley). The earliest in the human branch is Orrorin tugenensis (Millennium Man, Kenya). Chimpanzees and humans share 98% of DNA: biochemical similarities are so great that their hemoglobin molecules differ by only one amino acid. One group of chimps can have more genetic diversity than all of the six billion humans alive today, due to later population bottlenecking on the human lineage. Both chimpanzees and humans have a larynx that repositions during the first two years of life to a spot between the pharynx and the lungs, indicating that the common ancestors have this feature, a precursor of speech.
4.8 Ma Chimpanzee size hominin genus, Ardipithecus walks upright
3.7 Ma Some Australopithecus afarensis leave footprints on volcanic ash in Laetoli, Kenya (Northern Tanzania).
3.5 Ma Orangutans diverge into Bornean (Pongo pygmaeus) and Sumatran (Pongo abelii) sub-species. Great white sharks appear.
3 Ma

The bipedal australopithecines (early hominins) evolve in the savannas of Africa being hunted by Dinofelis. Species include Australopithecus africanus, Australopithecus bosei. Other genera include Kenyanthropus platyops. Gorillas die out on the South bank of the Congo River. North and South America become joined, allowing migration of animals. Modern horses, Equus first appear. Deinotherium (4 m tall), is a gigantic cousin of the elephant, with downward pointing tusks in the lower jaw.
2.5 Ma Smilodon (Saber-toothed cat) appears.
2.2 Ma Gorillas diverge into the Western lowland (Gorilla gorilla) and Eastern (Gorilla beringei) sub-species.
2 Ma Homo habilis (handy man) uses primitive stone tools (choppers) in Tanzania. Probably lives with Paranthropus robustus. Emergence of Broca's area (speech region of modern human brain). Homo species are meat-eating while Paranthropus eats plants and termites. Some chimpanzees (Pan troglodytes) at the Southern part of the Congo River branch off to form the Bonobos (Pan paniscus/pigmy chimps). Bonobos live in female dominated society. Saber Tooth moves from North America to South America.
1.8 Ma Homo erectus evolves in Africa and migrates to other continents, primarily South Asia. A large-scale extinction of marine life is triggered by some event, possibly a supernova. Many seabirds, which have dominated the shores and coastal waters for some 20 million years, become extinct; marine mammals diversify and take their place.
1.75 Ma Dmanisi man/Homo georgicus (Georgia, Russia), tiny brain came from Africa, with Homo erectus and Homo habilis characteristics. An individual spent the last years of his life with only one tooth by depending on the kindness and compassion of others to obtain sufficient sustenance.

The glyptodon, a giant armadillo the size of a Volkswagen Beetle, lives in southern Peru.
1.6 Ma Biggest marsupials: Appearance of Giant Short-faced Kangaroo (Procoptodon goliah) in Australia, extinct by 40,000 years ago. At 2 m to 3 m tall and weighing 200 kg to 300 kg, it is the largest kangaroo ever known. Wombat-like Diprotodon optatum, 2,800 kg, 3 m long, Australia, extinct by 45,000 years ago.
1.5 Ma Marsupial lion (Thylacoleo carnifex or Leo) appears in Australia and goes extinct by 46,000 years ago.
1 Ma Genus Canis (coyotes, jackals, wolves, dingoes, domestic dogs) develops as a branch from Tomarctus. The gray fox, Urocyon cinereoargenteus is the most primitive canid still alive today.
800 ka Gray Wolf (Canis lupus) moves to Arctic North America.
780 ka The Earth's last (most recent) geomagnetic reversal.
700 ka Common genetic ancestor of humans and Neanderthals.
500 ka Homo erectus (Choukoutien, China) uses charcoal to control fire, though they may not know how to create or start it.
400 ka Eastern gorillas (Gorilla beringei) diverge into the eastern lowland (G. beringei graueri) and mountain (G. beringei beringei) sub-species. Giant deer Megaloceros giganteus, Ireland; the antlers together span about 3.6 m or larger, extinct by 9.5 ka.
355 ka Three 1.5 m tall Homo heidelbergensis scramble down Roccamonfina volcano in Southern Italy, leaving the earliest known Homo footprints, which were made before the powdery volcanic ash solidified.
250 ka The Polar Bear evolves from an isolated high latitude population of Brown Bears.
195 ka Omo1, Omo2 (Ethiopia, Omo river) are the earliest known Homo sapiens.
160 ka Homo sapiens (Homo sapiens idaltu) in Ethiopia, Awash River, Herto village, practise mortuary rituals and butcher hippos. Their dead bodies are later covered by volcanic rocks.
150 ka "Mitochondrial Eve" lives in Africa. She is the last female ancestor common to all mitochondrial lineages in humans alive today.
130 ka Homo neanderthalensis (Neanderthal man) evolves from Homo heidelbergensis and lives in Europe and the Middle East, buries the dead and cares for the sick. Has hyoid bone (60,000 yrs ago, Kebara cave, Israel), used for speech in modern humans. (Today humans use roughly 6000 spoken languages). Uses spear, probably for stabbing rather than throwing. FOXP2 gene appears (associated with the development of speech).
100 ka The first anatomically modern humans (Homo sapiens) appear in Africa by this time or earlier; they derive from Homo heidelbergensis. Homo sapiens (humans) live in South Africa (Klasies River Mouth) and Palestine (Qafzeh and Es Skhul), probably alongside Neanderthals. Modern humans enter Asia via two routes: one North through the Middle East, and another further South from Ethiopia, via the Red Sea and southern Arabia. (See: Single-origin hypothesis). Mutation causes skin color changes in order to absorb optimal UV light for different geographical latitudes. Modern "race" formation begins. African populations remain more 'diverse' in their genetic makeup than all other humans, since only a subset of their population (and therefore only a subset of their diversity) leaves Africa. For example, mtDNA shows that an individual with English ancestors is more similar genetically to an individual with Japanese ancestors than are two individuals drawn from two African populations.
82.5 ka Humans in Zaire fish using sharp blades spears made from animal bones.
80 ka Humans make bone harpoons in Katanda, Democratic Republic of Congo.
74 ka Supervolcanoic eruption in Toba, Sumatra, Indonesia, causes Homo sapiens population to crash to 2,000. Six years without a summer are followed by a 1,000 year ice-age. Volcanic ash up to 5 m deep covers India and Pakistan.
70 ka The most recent ice age, the Wisconsin glaciation, begins.

Humans in the Blombos cave in South Africa make tools from bones, show symbolic thinking by creating ochre paintings. They also collect and pierce holes through sea shells to make necklaces. Giant beavers (Castoroides ohioensis, Toronto, Canada) largest rodents, length up to 2.5 m, dies out 10,000 years ago.
60 ka "Y-chromosomal Adam" lives in Africa. He is the last common male ancestor of all humans alive today.
50 ka Modern humans expand from Asia to Australia (to become today's Indigenous Australians) and Europe. Expansion along the coasts happens faster than expansion inland. Woolly rhino (Coelodonta antiquus) in Britain.
40 ka Cro-Magnon Humans paint and hunt mammoths in France. They have extraordinary cognitive powers equivalent to modern humans, which enable them to become predators/hunters at the top of the food chain. Megafauna extinction starts (continuing to current day); most large mammal species disappear, directly or indirectly due to the expanding human population.[26]
32 ka First sculpture found in Vogelherd, Germany. First (bird bone) flute found in France. Stone tools in Kota Tampan, Malaysia.
30 ka Modern humans enter North America from Siberia in numerous waves, some later waves across the Bering land bridge, but early waves probably by island-hopping across the Aleutians. At least two of the first waves left few or no genetic descendants among Americans by the time Europeans arrive across the Atlantic Ocean. Humans reach Solomon Islands and Japan. Bow and arrows used in Sahara (grassland). Fired ceramic animal models made in Moravia (Czech Republic).
28 ka Oldest known painting: in the Apollo 11 Rock Shelter[27]., Namibia, Africa. A 20 cm-long, 3 cm-wide object found in Hohle Fels Cave near Ulm in the Swabian Jura in Germany is the earliest sculpted stone penis[28].
27 ka Neanderthals die out leaving Homo sapiens and Homo floresiensis as the only living species of the genus Homo. In today's Czech Republic, humans invent textiles and press weaving patterns into pieces of clay before firing them.
25 ka Throwing sticks for hunting animals made from mammoth tusk (Poland).
23 ka Venus of Willendorf, a small statuette of a female figure, discovered at a paleolithic site near Willendorf, Austria, dates from this era. First intentional growing of food plants by humans occurs in the Near East, but is not associated with land clearing or tillage.
20 ka Humans leave foot and hand prints in Tibetan plateau. Oil lamps made from animal fats on shells used in caves in Grotte de la Mouthe, France. Bone needles used to sew animal hides. (Shandingdong Man, China). Microblade culture (Northern China). Mammoth bones used to build houses (Russia).
18 ka Homo floresiensis existed in the Liang Bua limestone cave on Flores, remote Indonesian island.
15 ka The last Ice Age ends. Sea levels across the globe rise, flooding many coastal areas, and separating former mainland areas into islands. Japan separates from Asia mainland. Siberia separates from Alaska. Tasmania separates from Australia. Java island forms. Sarawak, Malaysia and Indonesia separate. The cave paintings of Lascaux and Altamira were produced. Sedentary hunter-gather societies develop in the Natufian culture of the Near East - an essential precursor to later agricultural societies.
14 ka Megafauna extinction starts in the Americas.
11.5 ka Extinction of the Sabertooth (Smilodon) and Merriam's Teratorn (the "thunderbird").
11 ka Human population reaches 5 million. Extinction of Homo floresiensis.

Extinction of woolly mammoth. Domestication of dogs (first domesticated animal) from Gray Wolf subspecies (Canis lupus pallipes). All modern dogs today (5 main groups, about 400 breeds) belong to a single subspecies Canis lupus familiaris.
10 ka Humans in the Fertile Crescent of the Middle East develop agriculture. Plant domestication begins with cultivation of Neolithic founder crops. This process of food production, coupled later with the domestication of animals caused a massive increase in human population that has continued to the present. Jericho (modern Israel) settlement with about 19,000 people.
10 ka Sahara is green with rivers, lakes, cattles, crocodiles and monsoons. Japan's hunter-gatherer Jomon culture creates world's earliest pottery. Humans reach Tierra del Fuego at the tip of South America, the last continental region to be inhabited by humans (excluding Antarctica).
8 ka Common (Bread) wheat Triticum aestivum originates in southwest Asia due to hybridisation of emmer wheat with a goat-grass, Aegilops tauschii.
6.5 ka Two rice species are domesticated: Asian rice Oryza sativa and African rice Oryza glaberrima.
3.5 ka Humans in Mesoamerica develop the foundations of organized religion, with initiated priests overseeing rituals.
3 ka Humans in Eurasia start using iron tools.
AD 1 Human population 150 million.
AD 1835 Human population 1 billion.
AD 1969 Humans walk on the moon.
AD 2006 Human population approaching 6.6 billion.[29]

Holocene extinction event continues (commencing 30-40 ka) with the observed rate of extinction rising dramatically in the last 50 years. Most biologists believe[30] that we are at this moment at the beginning of a tremendously accelerated anthropogenic mass extinction. Wilson[31] estimates that at current rates of human destruction of the biosphere, one-half of all species of life will be extinct in 100 years.

[edit] See also

[edit] References

  1. ^ Planetary Science Institute page on the Giant Impact Hypothesis. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.
  2. ^ "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." How the Oceans Formed (URL accessed on January 9, 2005)
  3. ^ " 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" Geophysicist Sleep: Martian underground may have harbored early life (URL accessed on January 9, 2005)
  4. ^ Walker, Gabrielle, (2003) "Snowball Earth: The Story of the Great Global Catastrophe that Spawned Life as we know it" Bloomsbury ISBN 0-7476-5433-7
  5. ^ John, Brian (Ed)(1979) "The Winters of the World: Earth under the Ice Ages" Jacaranda Press ISBN 0-470-26844-1
  6. ^ "'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." Sex Speeds Up Evolution, Study Finds (URL accessed on January 9, 2005)
  7. ^ " What, then, was the selective advantage that led to the evolution of multicellular organisms?" From Single Cells to Multicellular Organisms (URL accessed on January 9, 2005)
  8. ^ "The evolutionary foundation for the organization of many animal body plans is segmental—we are made of rings of similar stuff, repeated over and over again along our body length" Pycnogonid tagmosis and echoes of the Cambrian
    "Pycnogonids are primitive chelicerates related to ticks and mites, and they make their living as predators and scavengers. This one, Haliestes dasos, is the oldest sea spider known." Haliestes dasos, a sea spider
    "If you were a trilobite or other small Cambrian animal, you did NOT want to see this coming" The Anomalocaris Homepage (animation)
  9. ^ "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 animals 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." Oldest fossil footprints on land
  10. ^ 1
  11. ^ "The oldest fossils reveal evolution of non-vascular plants by the middle to late Ordovician Period (~450-440 m.y.a.) on the basis of fossil spores" Transition of plants to land
  12. ^ "The land plants evolved from the algae, more specifically green algae, as suggested by certain common biochemical traits" The first land plants
  13. ^ "The waxy cuticle of arachnids and insects prevents water loss and protects against desiccation" Natural history collection: arthropoda
  14. ^ "For hundreds of millions of years, animal life resided only in the oceans. And then about 400 million years ago, fossil tracks suggest that an animal called a eurypterid left the water to walk on land. Maybe it was fleeing enemies, maybe it was searching for an easy meal, or maybe it was seeking a safe place to lay its eggs." The shape of life. The conquerors. PBS
  15. ^ "The ancestry of sharks dates back more than 200 million years before the earliest known dinosaur. Introduction to shark evolution, geologic time and age determination
  16. ^ "Cladoselache was something of an oddball among ancient sharks. A four-foot (1.2-metre) long inhabitant of late Devonian seas (about 370 million years ago), it exhibited a strange combination of ancestral and derived characteristics. Ancient sharks
  17. ^ "Sharks have undergone a lot of evolutionary experimentation since their earliest beginnings. Over hundreds of millions of years, sharks were tested by a mercurial and often violently changeable environment." A Golden Age of Sharks
  18. ^ “Here we report the isolation and growth of a previously unrecognized spore-forming bacterium (Bacillus species, designated 2-9-3) from a brine inclusion within a 250 million-year-old salt crystal from the Permian Salado Formation. Complete gene sequences of the 16S ribosomal DNA show that the organism is part of the lineage of Bacillus marismortui and Virgibacillus pantothenticus.” Isolation of a 250 million-year-old halotolerant bacterium from a primary salt crystal (URL accessed on April 30, 2006)
  19. ^ "The second major radiation of sharks occurred during the Jurassic Period, 208 to 144 million years ago. At this time, pterosaurs ruled the skies and the first birds were taking to the air." The Origin of Modern Sharks (URL accessed on January 9, 2005)
  20. ^ "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." Origins of Viruses (URL accessed on January 9, 2005)
  21. ^ "A comparison of the two genomes reveals that both have about 30,000 genes, and they share the bulk of them—the human genome shares 99% of its genes with mice. Humans and mice diverged about 75 million years ago, too little time for many evolutionary differences to accumulate." Comparing genomes
    " Their conclusion: although the mouse and human genomes are very similar, genome rearrangements occurred more commonly than previously believed, accounting for the evolutionary distance between human and mouse from a common ancestor 75 million years ago." The Hindu
    "Mice have many more olfactory genes compared to the human. Smell matters for mice, especially for sex and mating; they also have more genes involved in reproduction (such as aphrodisin, which stimulates mating behaviour in males) and immunity" San Francisco Chronicle
  22. ^ "I also wish to completely dispel the myth that the modern Great White evolved from the megalodon shark. Is the proper way to do this to write this paper, publish it in a scientific journal, and subject it to peer review—yes? Is that what I am doing—no.......because I think there is no way to "win" with the opinions on this one as set in stone as they seem to be (on both sides)" Origin of the Modern Great White Shark (URL accessed on January 9, 2005)
    "'Most scientists would probably say the Great Whites evolved from the megalodon line, which existed from two million to twenty million years ago. They were huge sharks, approximately the length of a Greyhound bus and possessing teeth that were up to six inches [150 mm] long,' explains Ciampaglio. 'However, our research, which is based on analyzing fossils of several hundred shark teeth, shows that the Great White shares more similarities with the mako shark.'"Great White Shark Evolution Debate (URL accessed on January 9, 2005)
    ".. most paleontologists agree [..] that Megalodon is not a direct ancestor of the modern White Shark, more like a great uncle or aunt." The Origin of Megalodon (URL accessed on January 9, 2005)
  23. ^ "Researchers have discovered fossilized remains of two previously unknown primate species that lived 37 million years ago in what is now the Egyptian desert." "The discovery, researchers say, is evidence that the common ancestor of living anthropoids arose in Africa and that anthropoids have been evolving on the now separated Africa-Arabia landmass for at least 45 million years." New Primate Fossils Support "Out of Africa" Theory (URL accessed on January 9, 2005)
  24. ^ " Once humans could see in color the visual inspection of a potential mate yielded far more useful information and at a greater distance than was the case with scents. As a result of natural selection color-seeing primates came to have neuronal wiring that caused them to place much more importance on appearance in mate choice. In Zhang's view it is therefore not coincidental that around the time human males developed the ability to see color humans also lost the ability to respond to pheromones" Evolution Of Color Eyesight Led To Loss Of Pheromone Response (URL accessed on January 9, 2005)
  25. ^ ""'At a length of 50 feet (15 metres) and a mass of over 52 tons (47 tonnes), it would take more than a mere morsel to satisfy the megalodon.'"" The Origin of Megalodon (URL accessed on January 9, 2005)
  26. ^ Leakey, Richard and Roger Lewin, 1996, The Sixth Extinction : Patterns of Life and the Future of Humankind, Anchor, ISBN 0-385-46809-1
  27. ^ "These stones were found in association with charcoal which has been dated to between 19,000 and 26,000 years old (Wendt 1974, 1976). Border Cave in Kwazulu has yielded engraved bone and wood dated between 35,000 and 37,500 years old (Butzer et al 1979); and a 20,000 year old incised stone was found at Matupi Cave, Zaire (Van Noten 1977)." Introduction to upper palaeolithic art (URL accessed on January 9, 2005)
  28. ^ "The 20 cm-long, 3 cm-wide stone object, which is dated to be about 28,000 years old, was buried in the famous Hohle Fels Cave near Ulm in the Swabian Jura. " Ancient phallus unearthed in cave (URL accessed on January 9, 2005)
  29. ^ An United States Census Bureau estimate of the number of people alive on Earth at any given moment. United States census bureau
  30. ^ The American Museum of Natural History National Survey Reveals Biodiversity Crisis (URL accessed on February 23, 2006)
  31. ^ E.O. Wilson, Harvard University, The Future of Life (2002)

[edit] External links

Basic topics in evolutionary biology
v • d • e
Evidence of evolution
Processes of evolution: adaptation - macroevolution - microevolution - speciation
Population genetic mechanisms: selection - genetic drift - gene flow - mutation
Evo-devo concepts: phenotypic plasticity - canalisation - modularity
Modes of evolution: anagenesis - catagenesis - cladogenesis
History: History of evolutionary thought - Charles Darwin - The Origin of Species - modern evolutionary synthesis
Other subfields: ecological genetics - human evolution - molecular evolution - phylogenetics - systematics
List of evolutionary biology topics | Timeline of evolution
Retrieved from "http://en.wikipedia.org../../../t/i/m/Timeline_of_evolution.html"