Timeline of human evolution
The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens,
throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period.
It includes brief explanations of the various taxonomic ranks in the human lineage. The timeline reflects the mainstream views in modern taxonomy, based on the principle of phylogenetic nomenclature;
in cases of open questions with no clear consensus, the main competing possibilities are briefly outlined.
Overview of taxonomic ranks
A tabular overview of the taxonomic ranking of Homo sapiens is shown below.Timeline
Tetrapoda
| Date | Event |
| 390 Ma | Some freshwater lobe-finned fish develop limbs and give rise to the Tetrapodomorpha. These fish evolved in shallow and swampy freshwater habitats, where they evolved large eyes and spiracles. Primitive tetrapods developed from tetrapodomorphs with a two-lobed brain in a flattened skull, a wide mouth and a medium 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. Tetrapod fishes used their fins as paddles in shallow-water habitats choked with plants and detritus. The universal tetrapod characteristics of front limbs that bend backward at the elbow and hind limbs that bend forward at the knee can plausibly be traced to early tetrapods living in shallow water. Panderichthys is a 90–130 cm long fish from the Late Devonian period. It has a large tetrapod-like head. Panderichthys exhibits features transitional between lobe-finned fishes and early tetrapods. Trackway impressions made by something that resembles Ichthyostega's limbs were formed 390 Ma in Polish marine tidal sediments. This suggests tetrapod evolution is older than the dated fossils of Panderichthys through to Ichthyostega. |
| 375-350 Ma | Tiktaalik is a genus of sarcopterygian fishes from the late Devonian with many tetrapod-like features. It shows a clear link between Panderichthys and Acanthostega. Acanthostega is an extinct tetrapod, among the first animals to have recognizable limbs. It is a candidate for being one of the first vertebrates to be capable of coming onto land. It lacked wrists, and was generally poorly adapted for life on land. The limbs could not support the animal's weight. Acanthostega had both lungs and gills, also indicating it was a link between lobe-finned fish and terrestrial vertebrates. The dorsal pair of ribs form a rib cage to support the lungs, while the ventral pair disappears. Ichthyostega is another extinct tetrapod. Being one of the first animals with only two pairs of limbs, Ichthyostega is seen as an intermediate between a fish and an amphibian. Ichthyostega had limbs but these probably were not used for walking. They may have spent very brief periods out of water and would have used their limbs to paw their way through the mud. They both had more than five digits at the end of each of their limbs, and their bodies were scaleless. Many evolutionary changes occurred at this stage: eyelids and tear glands evolved to keep the eyes wet out of water and the eyes became connected to the pharynx for draining the liquid; the hyomandibula shrank into the spiracle, which now also connected to the inner ear at one side and the pharynx at another, becoming the Eustachian tube ; an early eardrum evolved on the end of each tube ; and the ceratohyal and basihyal merged into the hyoid. These "fishapods" had more ossified and stronger bones to support themselves on land. Jaw bones fuse together while gill and opercular bones disappear. |
| 350-330 Ma | Pederpes from around 350 Ma indicates that the standard number of 5 digits evolved at the Early Carboniferous, when modern tetrapods split in two directions. At this stage, our ancestors evolved vomeronasal organs, salivary glands, tongues, parathyroid glands, three-chambered hearts and bladders, and completely removed their gills by adulthood. The glottis evolves to prevent food going into the respiratory tract. Lungs and thin, moist skin allowed them to breathe; water was also needed to give birth to shell-less eggs and for early development. Dorsal, anal and tail fins all disappeared. Lissamphibia retain many features of early amphibians but they have only four digits. |
| 330-300 Ma | From amphibians came the first amniotes: Hylonomus, a primitive reptile, is the earliest amniote known. It was 20 cm long and probably would have looked rather similar to modern lizards. It had small sharp teeth and probably ate small millipedes and insects. It is a precursor of later amniotes. Alpha keratin first evolves here; it is used in the claws of modern amniotes, and hair in mammals, indicating claws and a different type of scales evolved in amniotes. Evolution of the amniotic egg allows the amniotes to reproduce on land and lay shelled eggs on dry land. They did not need to return to water for reproduction nor breathing. This adaptation and the desiccation-resistant scales gave them the capability to inhabit the uplands for the first time, albeit making them drink water through their mouths. At this stage, adrenal tissue may have concentrated into discrete glands. Amniotes have advanced nervous systems, with twelve pairs of cranial nerves, unlike lower vertebrates. They also evolved true sternums but lost their eardrums and otic notches. |
Mammalia
| Date | Event |
| 300-260 Ma | Shortly after the appearance of the first amniotes, two branches split off. One branch is the Sauropsida, from which come the reptiles, including birds. The other branch is Synapsida, from which come modern mammals. Both had temporal fenestrae, a pair of holes in their skulls behind the eyes, which were used to increase the space for jaw muscles. Synapsids had one opening on each side, while diapsids had two. An early, inefficient version of diaphragm may have evolved in synapsids. The earliest synapsids, or "proto-mammals," are the pelycosaurs. The pelycosaurs were the first animals to have temporal fenestrae. Pelycosaurs were not therapsids but their ancestors. The therapsids were, in turn, the ancestors of mammals. The therapsids had temporal fenestrae larger and more mammal-like than pelycosaurs, their teeth showed more serial differentiation, their gait was semi-erect and later forms had evolved a secondary palate. A secondary palate enables the animal to eat and breathe at the same time and is a sign of a more active, perhaps warm-blooded, way of life. They had lost gastralia and, possibly, scales. |
| 260-230 Ma | One subgroup of therapsids, the cynodonts, lose pineal eye and lumbar ribs and very likely became warm-blooded. The lower respiratory tract forms intricate branches in the lung parenchyma, ending in highly vascularized alveoli. Erythrocytes and thrombocytes lose their nuclei while lymphatic systems and advanced immunity emerge. They may have also had thicker dermis like mammals today. The jaws of cynodonts resembled modern mammal jaws; the anterior portion, the dentary, held differentiated teeth. This group of animals likely contains a species which is the ancestor of all modern mammals. Their temporal fenestrae merged with their orbits. Their hindlimbs became erect and their posterior bones of the jaw progressively shrunk to the region of the columella. |
| 230-170 Ma | From Eucynodontia came the first mammals. Most early mammals were small shrew-like animals that fed on insects and had transitioned to nocturnality to avoid competition with the dominant archosaurs — this led to the loss of the vision of red and ultraviolet light. Although there is no evidence in the fossil record, it is likely that these animals had a constant body temperature, hair and milk glands for their young. The neocortex region of the brain evolves in Mammalia, at the reduction of the tectum. Origin of the prostate gland and a pair of holes opening to the columella and nearby shrinking jaw bones; new eardrums stand in front of the columella and Eustachian tube. The skin becomes hairy, glandular and thermoregulatory. Teeth fully differentiate into incisors, canines, premolars and molars; mammals become diphyodont and possess developed diaphragms and males have internal penises. All mammals have four chambered hearts and lack cervical ribs. Monotremes are an egg-laying group of mammals represented today by the platypus and echidna. Recent genome sequencing of the platypus indicates that its sex genes are closer to those of birds than to those of the therian mammals. Comparing this to other mammals, it can be inferred that the first mammals to gain sexual differentiation through the existence or lack of SRY gene evolved only in the therians. Early mammals and possibly their eucynodontian ancestors had epipubic bones, which serve to hold the pouch in modern marsupials. |
| 170-120 Ma | Evolution of live birth, with early therians probably having pouches for keeping their undeveloped young like in modern marsupials. Nipples stemmed out of the therian milk lines. The posterior orifice separates into anal and urogenital openings; males possess an external penis. Monotremes and therians independently detach the malleus and incus from the dentary and combine them to the shrunken columella in the tympanic cavity behind the eardrum, and coil their lagena to advance their hearing, with therians further evolving an external pinna and erect forelimbs. Female placentalian mammals do not have pouches and epipubic bones but instead have a developed placenta which penetrates the uterus walls, allowing a longer gestation; they also have separated urinary and genital openings. |
| 100-90 Ma | Last common ancestor of rodents, rabbits, ungulates, carnivorans, bats, shrews and humans. |
Primates
| Date | Event |
| 90–66 Ma | A group of small, nocturnal, arboreal, insect-eating mammals called Euarchonta begins a speciation that will lead to the orders of primates, treeshrews and flying lemurs. They reduced the number of mammaries to only two pairs. Primatomorpha is a subdivision of Euarchonta including primates and their ancestral stem-primates Plesiadapiformes. An early stem-primate, Plesiadapis, still had claws and eyes on the side of the head, making it faster on the ground than in the trees, but it began to spend long times on lower branches, feeding on fruits and leaves. The Plesiadapiformes very likely contain the ancestor species of all primates. They first appeared in the fossil record around 66 million years ago, soon after the Cretaceous–Paleogene extinction event that eliminated about three-quarters of plant and animal species on Earth, including most dinosaurs. One of the last Plesiadapiformes is Carpolestes simpsoni, having grasping digits but not forward-facing eyes. |
| 66-56 Ma | Primates diverge into suborders Strepsirrhini and Haplorrhini. Brain expands and cerebrum divides into 4 pairs of lobes. The postorbital bar evolves to separate the orbit from the temporal fossae as sight regains its position as the primary sense; eyes became forward-facing. Strepsirrhini contain most prosimians; modern examples include lemurs and lorises. The haplorrhines include the two living groups: prosimian tarsiers, and simian monkeys, including apes. The Haplorrhini metabolism lost the ability to produce vitamin C, forcing all descendants to include vitamin C-containing fruit in their diet. Early primates only had claws in their second digits; the rest were turned into nails. |
| 50-35 Ma | Simians split into infraorders Platyrrhini and Catarrhini. They fully transitioned to diurnality and lacked any claw and tapetum lucidum. They possibly evolved at least some of the paranasal sinuses, and transitioned from estrous cycle to menstrual cycle. The number of mammaries is now reduced to only one thoracic pair. Platyrrhines, New World monkeys, have prehensile tails and males are color blind. The individuals whose descendants would become Platyrrhini are conjectured to have migrated to South America either on a raft of vegetation or via a land bridge. Catarrhines mostly stayed in Africa as the two continents drifted apart. Possible early ancestors of catarrhines include Aegyptopithecus and Saadanius. |
| 35-20 Ma | Catarrhini splits into 2 superfamilies, Old World monkeys and apes. Human trichromatic color vision had its genetic origins in this period. Catarrhines lost the vomeronasal organ. Proconsul was an early genus of catarrhine primates. They had a mixture of Old World monkey and ape characteristics. Proconsul's monkey-like features include thin tooth enamel, a light build with a narrow chest and short forelimbs, and an arboreal quadrupedal lifestyle. Its ape-like features are its lack of a tail, ape-like elbows, and a slightly larger brain relative to body size. Proconsul africanus is a possible ancestor of both great and lesser apes, including humans. |
Homo
| Date | Event |
| 2.8–2.0 Ma | Early Homo appears in East Africa, speciating from australopithecine ancestors. The Lower Paleolithic is defined by the beginning of use of stone tools. Australopithecus garhi was using stone tools at about 2.5 Ma. Homo habilis is the oldest species given the designation Homo, by Leakey et al. in 1964. H. habilis is intermediate between Australopithecus afarensis and H. erectus, and there have been suggestions to re-classify it within genus Australopithecus, as Australopithecus habilis. LD 350-1 is now considered the earliest known specimen of the genus Homo, dating to 2.75–2.8 Ma, found in the Ledi-Geraru site in the Afar Region of Ethiopia. It is currently unassigned to a species, and it is unclear if it represents the ancestor to H. habilis and H. rudolfensis, which are estimated to have evolved around 2.4 Ma. Stone tools found at the Shangchen site in China and dated to 2.12 million years ago are considered the earliest known evidence of hominins outside Africa, surpassing Dmanisi hominins found in Georgia by 300,000 years, although whether these hominins were an early species in the genus Homo or another hominin species is unknown. |
| 1.9–0.8 Ma | Homo erectus derives from early Homo or late Australopithecus. Homo habilis, although significantly different of anatomy and physiology, is thought to be the ancestor of Homo ergaster, or African Homo erectus; but it is also known to have coexisted with H. erectus for almost half a million years. From its earliest appearance at about 1.9 Ma, H. erectus is distributed in East Africa and Southwest Asia. H. erectus is the first known species to develop control of fire, by about 1.5 Ma. H. erectus later migrates throughout Eurasia, reaching Southeast Asia by 0.7 Ma. It is described in a number of subspecies. Early humans were social and initially scavenged, before becoming active hunters. The need to communicate and hunt prey efficiently in a new, fluctuating environment may have driven the expansion of the brain from 2 to 0.8 Ma. Evolution of dark skin at about 1.2 Ma. Homo antecessor may be a common ancestor of Homo sapiens and Neanderthals. At present estimate, humans have approximately 20,000–25,000 genes and share 99% of their DNA with the now extinct Neanderthal and 95–99% of their DNA with their closest living evolutionary relative, the chimpanzees. The human variant of the FOXP2 gene has been found to be identical in Neanderthals. |
| 0.8–0.3 Ma | Divergence of Neanderthal and Denisovan lineages from a common ancestor. Homo heidelbergensis had long been thought to be a likely candidate for the last common ancestor of the Neanderthal and modern human lineages. However, genetic evidence from the Sima de los Huesos fossils published in 2016 seems to suggest that H. heidelbergensis in its entirety should be included in the Neanderthal lineage, as "pre-Neanderthal" or "early Neanderthal", while the divergence time between the Neanderthal and modern lineages has been pushed back to before the emergence of H. heidelbergensis, to about 600,000 to 800,000 years ago, the approximate age of Homo antecessor. Brain expansion between 0.8 and 0.2 Ma may have occurred due to the extinction of most African megafauna, extreme climate variability after Mid-Pleistocene Transition, and in general selection for more social life for greater chance of survival, reproductivity, and care for mothers. Solidified footprints dated to about 350 ka and associated with H. heidelbergensis were found in southern Italy in 2003. H. sapiens lost the brow ridges from their hominid ancestors as well as the snout completely, though their noses evolve to be protruding. By 200 ka, humans had stopped their brain expansion. |
Homo sapiens
| Date | Event |
| 300–130 ka | Neanderthals and Denisovans emerge from the northern Homo heidelbergensis lineage around 500-450 ka while sapients emerge from the southern lineage around 350-300 ka. Fossils attributed to H. sapiens, along with stone tools, dated to approximately 300,000 years ago, found at Jebel Irhoud, Morocco yield the earliest fossil evidence for anatomically modern Homo sapiens. Modern human presence in East Africa, at 276 kya. In July 2019, anthropologists reported the discovery of 210,000 year old remains of what may possibly have been a H. sapiens in Apidima Cave, Peloponnese, Greece. Patrilineal and matrilineal most recent common ancestors of living humans roughly between 200 and 100 kya with some estimates on the patrilineal MRCA somewhat higher, ranging up to 250 to 500 kya. 160,000 years ago, Homo sapiens idaltu in the Awash River Valley practiced excarnation. |
| 130–80 ka | Marine Isotope Stage 5. Modern human presence in Southern Africa and West Africa. Appearance of mitochondrial haplogroup L2. |
| 80–50 ka | MIS 4, beginning of the Upper Paleolithic. Early evidence for behavioral modernity. Appearance of mt-haplogroups M and N. Southern Dispersal migration out of Africa, Proto-Australoid peopling of Oceania. Archaic admixture from Neanderthals in Eurasia, from Denisovans in Oceania with trace amounts in Eastern Eurasia, and from an unspecified African lineage of archaic humans in Sub-Saharan Africa as well as an interbred species of Neanderthals and Denisovans in Asia and Oceania. |
| 50–25 ka | Behavioral modernity develops by this time or earlier, according to the "great leap forward" theory. Extinction of Homo floresiensis. M168 mutation. Appearance of mt-haplogroups U and K. Peopling of Europe, peopling of the North Asian Mammoth steppe. Paleolithic art. Extinction of Neanderthals and other archaic human variants . Appearance of Y-Haplogroup R2; mt-haplogroups J and X. |
| after 25 ka | Last Glacial Maximum; Epipaleolithic / Mesolithic / Holocene. Peopling of the Americas. Appearance of: Y-Haplogroup R1a; mt-haplogroups V and T. Various recent divergence associated with environmental pressures, e.g. light skin in Europeans and East Asians, after 30 ka; Inuit adaptation to high-fat diet and cold climate, 20 ka. Extinction of late surviving archaic humans at the beginning of the Holocene. Accelerated divergence due to selection pressures in populations participating in the Neolithic Revolution after 12 ka, e.g. East Asian types of ADH1B associated with rice domestication, or lactase persistence. The past 100,000 years have seen selective reductions in brain size for some human lineages during warmer interglacial periods. |