Timeline of evolution This timeline outlines the major events in the development of life on planet Earth. For context, see biology, evolution and the geologic timescale. Dates given are estimates. The table uses the abbreviations "MYA" for "million years ago" and "kYA" for "thousand years ago." Timeline Life on Earth Date Event 4500 MYA The planet Earth forms from the accretion disk revolving around the young Sun. 4100 MYA The surface of the Earth cools down enough for the crust to solidify. 4000 MYA Life appears, probably first as self-reproducing RNA molecules. The atmosphere does not contain any free oxygen (See: origin of life). 3900 MYA Cells resembling prokaryotes appear. Central dogma of biology: DNA-> RNA-> Protein. Three bases -> One amino acid. One gene -> One protein. 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 employs ATP molecules as short term energy currency and is used in almost all organisms unchanged to this day. Although mostly inconspicuous, prokaryotes remain the dominant life form on Earth even today. (See: evolution of prokaryotes) 3900 MYA The split between the bacteria and the archaea occurs. 3500 MYA 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 MYA Photosynthesizing cyanobacteria evolve; they use water as reductant, thereby producing oxygen as waste product. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. Then the oxygen concentration in the atmosphere rises, acting as a poison for many bacteria. 2500 MYA 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. 2100 MYA More complex cells appear: the eukaryotes, which contain various organelles. The closest relatives of these are probably the Archaea. Most have organelles which are probably derived from symbiotic bacteria: mitochondria, which use oxygen to extract energy from organic molecules and appear similar to today's Rickettsia, and often chloroplasts, which derive energy from light and synthesize organic molecules and originated from cyanobacteria and similar forms. 1200 MYA Sexual reproduction evolves and leads to an explosion in the rate of evolution. While most life occurs in oceans and lakes, some cyanobacteria may already have lived in moist soil by this time. 1000 MYA Multicellular organisms appear: initially colonial algae and later, seaweeds, living in the oceans. 600 MYA Sponges (Porifera), Jellyfish (Cnidaria), flat worms Platyhelminthes and other multicellular animals appear in the oceans. 565-525 MYA The Cambrian explosion, a rapid set of evolutionary changes, creates all the major body plans (phyla) of modern animals. 475 MYA The first primitive plants move onto land, having evolved from green algae living along the edges of lakes. They are accompanied by fungi, and very likely plants and fungi work symbiotically together. 450 MYA Arthropods, with an exoskeleton that provides support and prevents water loss, are the first animals to invade the land. Among the first are Myriapoda (millipedes and centipedes), later followed by spiders and scorpions. 365 MYA Insects evolve on land and in fresh water from the myriapods. Some fresh water lobe-finned fish (Sarcopterygii) develop legs and give rise to the Tetrapoda. This happens in the water; tetrapods then use their legs to move out onto land, probably to hunt insects. Lungs and swim bladders evolve. Amphibians still retain many characteristics of the early tetrapods. 360 MYA Plants evolve seeds, structures that protect plant embryos and enable plants to spread quickly on land. 300 MYA Evolution of the amniotic egg gives rise to the Amniota, reptiles who can reproduce on land. Insects evolve flight. Dragonflies (Odonata) still resemble these early insects. Vast forests of clubmosses (lycopods), horsetails, and tree ferns cover the land; when these decay they will eventually form coal. Gymnosperms begin to diversify widely. 250 MYA The Permian-Triassic extinction event wipes out about 95% of all animal species, the most severe mass extinction known. The archosaurs split from other reptiles. They will later diversify into crocodiles, dinosaurs, birds and pterosaurs. Teleosts evolve from among the Actinopterygii (ray-finned fish), and eventually become the dominant fish group. 220 MYA The climate is very dry, and dry-adapted organism are favored: the archosaurs and the Gymnosperms. The first mammals appear, which evolved from synapsid reptiles. Initially, they stay small. First mammals are reptile-like. Looks like present day platypus(monotremes). Constant body temperature. All mammals have milk glands for their young. One of a pair of autosomes acquire a SRY gene derived from SOX3 from 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 200 MYA Birds evolve from theropod dinosaurs. Modern amphibians evolve: the Lissamphibia; including Anura (frogs), Urodela (salamanders), and Caecilia 180 MYA 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 130 MYA Angiosperm plants evolve flowers, structures that attract insects and other animals to spread pollen. The evolution of the angiosperms cause a major burst of animal evolution. Half of all known dinosaur species are from the last 30 MY of the Mesozoic, after the rise of the angiosperms. 125 MYA Eomaia scansoria, a eutherian mammal, which leads to the formation of modern placental mammals. Looks like modern dormouse, climbing small shrubs in Liaoning, China. 100 MYA Common genetic ancestor of mice and humans. 65 MYA The Cretaceous-Tertiary 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 a meteor. Mammals increase in diversity and size. Some will later return back to the sea (whales, sirenians and seals) and others will evolve flight (bats). A group of small, nocturnal and arboreal, insect-eating mammals called the Archonta branches into the primates, tree shrews and bats. Primates have binocular vision and grasping digits. 55 MYA The earliest true primates, called euprimates, first appear in North America, Asia, and Europe. One eg is Carpolestes simpsoni at Clarks Fork Basin of Wyoming. It has grasping digits but no forward facing eyes. Another (earliest?) euprimate Teihardina asiatica (Hunan,China) is mouse-sized, diurnal and has small eyes. 45 MYA Cetaceans (whales) evolve from mesonychids, carnivorous ungulates probably most closely related to the artiodactyls. 40 MYA Primates (order) diverge into suborders Prosimians( a primitive monkey) and Anthropoids, the latter is diurnal and herbivorous. Examples of today's prosimians are tarsiers, lemurs, lorises. Lemurs cross the ocean into Madagascar from Africa mainland. 35 MYA Grasses evolve from among the angiosperms. 30 MYA Anthropoid (suborder) splits into infraorders New World Monkeys (Platyrrhini) and Catarrhini.( Old World Primates).New World Monkeys have prehensile tails and migrated to South America. Catarrhines stayed in Africa as the two continents drifted apart. One ancestor of catarrhines might be Aegyptopithecus. New world monkey males are color blind. 25 MYA Catarrhini males gain color vision but loses the pheromone pathway.Catarrhini (infraorder)( Old World Primates) splits into 2 superfamilies Old world monkeys( Cercopithecoidea ) and Hominoids. The Old world monkey does not have a prehensile tail e.g. Baboon. Some do not even have tails. All hominoids have no tails e.g. the lesser apes, great apes and hominids. 15 MYA Human ancestors speciate from the ancestors of the gibbon. Gibbons are lesser apes. Orangutans, gorilla and chimpanzees are great apes. Humans are hominids. 13 MYA Human ancestors speciate from the ancestors of the orangutan. A relative of orangutans:- Lufengpithecus chiangmuanensis (Northern Thailand). 10 MYA The climate begins to dry, savannas and grasslands take over the earlier 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 spread throughout the Northern hemisphere. After 10 MYA they decline in the face of competition with the artiodactyls. 5 MYA 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 similaritiies are so great that their hemoglobin molecules differ by only one amino acid, but that 2% difference explains why chimps do not contract AIDS and why they also cannot speak. One group of chimps can have more genetic diversity than all of the six billion humans alive today. Both chimpanzees and humans have 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. Buth humans and chimpanzees make friends, influence peers, get a date, win favors and form alliances and read facial expressions to tell the difference between a friend and an enemy, distinguish between the wimps from the bullies, and determine what's good behavior and what's bad. Each individual has its own personality, some more aggressive, some more social, and its own unique ability to navigate the social complexities of group living. They face the same problem of leaving home, finding a mate and making one's way in the world. 4.4 MYA Ardipithecus ramidus ramidus (hominid? walks upright most of the time? Still spend time on trees?) 3.7 MYA Some Australopithecus afarensis left footprints on volcanic ash in Laetoli, Kenya (Northern Tanzania). 3 MYA The bipedal australopithecines (early hominines) evolve in the savannas of Africa being hunted by Dinofelis. Species include Australopithecus africanus, Australopithecus bosei. Other genus include Kenyanthropus platyops. Gorillas die out on the south bank of the Congo River, and bonobos evolve from the chimpanzees there. North and South America become joined, allowing migration of animals. 2 MYA Homo habilis( handy man) uses primitive stone tools (choppers), Tanzania. Emergence of Broca's area( speech region of modern human brain). Probably lives with Australopithecus robustus (sometimes classified into genus Paranthropus). The Homos are meat-eating while the Australopithecine eat plants and termites 1.75 MYA Dmanisi man/ Homo georgicus (Georgia, Russia), tiny brain came from Africa, with Homo erectus and Homo habilis characteristics. 1800 kYA Homo erectus evolves in Africa and migrates to other continents, primarily south Asia. 500 kYA Homo erectus (Choukoutien, China) uses charcoal to control fire, though they may not know how to create or start it. 355 kYA Three 1.5m tall Homo heidelbergensis scrambled down Roccamonfina volcano in Southern Italy, leaving the earliest Homo footprints, which were made before the powdery volcanic ash solidified. 160 kYA Homo sapien (Homo sapien idaltu) in Ethiopia, Awash River, Herto village, practise mortuary rituals and butcher hippos. Their dead bodies are later covered by volcanic rocks. 150 kYA Birth of the mitochondria Eve in Africa. All humans are her descendents. 130 kYA Homo neanderthalensis evolves from Homo erectus and lives in Europe and the Middle East.Neanderthal man (Homo neanderthalensis) makes magic, bury the dead and care for the sick. Have hyoid bone (60,000 yrs ago, Kebara cave, Israel) used for speech in modern humans. (Today humans use roughly 6000 spoken languages). Use spear probably for stabbing rather than throwing. FOXP2 (speech gene) appears. 100 kYA The first anatomically modern humans (Homo sapiens) appear in Africa some time before this. They also evolved from Homo erectus. Modern humans enter Asia via the Middle East.(See: human evolution). Mutation causes skin color changes in order to absorb optimal UV light for different geographical latitudes . Modern "race" formation begins. 70 kYA The most recent ice age, the Wisconsin glaciation, begins. Humans in Blombos caves in South Africa make tools from bones, show symbolic thinking by using ochre (precursor to linguistic ability) 60 kYA Birth of Y-chromosome Adam in Africa. All humans are his descendents. 50 kYA Modern humans expand from Asia to Australia and Europe. Expansion along the coasts happens faster than expansion inland. 40 kYA Humans do painting and hunt mammoths in Cro-Magnon, France. They have extraordinary cognitive powers. Extinction of gigantic marsupials in Australia, probably due to humans. The result is the lack of domesticated animals, partially leading to the relatively backward life of the humans there later when compared to the rest of the world. 30 kYA 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 had left few or no genetic descendants among Americans by the time Europeans arrived across the Atlantic Ocean. 27 kYA Neanderthals die out leaving Homo sapiens and Homo erectus as the only living species of the genus Homo. 18 kYA Homo floresiensis existed on Flores Is. in Indonesia 15 kYA The last Ice Age ends. One group of humans in the Fertile Crescent of the Middle East develop agriculture and, along with it, permanent settlements and cities. These appear first in what is now Iraq. This process of food production caused a massive increase in human population that has continued to the present. 10 kYA Humans reach Tierra del Fuego at the tip of South America, the last continental region to be inhabited by humans (excluding Antarctica). 4 kYA Recorded history begins. 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