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.

Rank	Name	Common name	Started
	Life		4,200
	Archaea		3,700
Domain	Eukaryota	Eukaryotes	2,100
	Opimoda	Excludes Plants and their relatives	1,540
	Amorphea
	Obazoa	Excludes Amoebozoa
	Opisthokonta	Holozoa + Holomycota	1,300
	Holozoa	Excludes Holomycota	1,100
	Filozoa	Choanozoa + Filasterea
	Choanozoa	Choanoflagellates + Animals	900
Kingdom	Animalia	Animals	610
Subkingdom	Eumetazoa	Excludes Porifera
	Parahoxozoa	Excludes Ctenophora
	Bilateria	Triploblasts / Worms	560
	Nephrozoa
	Deuterostomia	Division from Protostomes
Phylum	Chordata	Chordates	530
	Olfactores	Excludes cephalochordates
Subphylum	Vertebrata	Fish / Vertebrates	505
Infraphylum	Gnathostomata	Jawed fish	460
	Teleostomi	Bony fish	420
	Sarcopterygii	Lobe finned fish
Superclass	Tetrapoda	Tetrapods	395
	Amniota	Amniotes	340
	Synapsida	Proto-Mammals	308
	Therapsida	Limbs beneath the body and other mammalian traits	280
Class	Mammalia	Mammals	220
Subclass	Theria	Mammals that give birth to live young	160
Infraclass	Eutheria	Placental mammals	125
Magnorder	Boreoeutheria	Supraprimates, hoofed mammals, carnivorous mammals, cetaceans, and bats	124–101
Superorder	Euarchontoglires	Supraprimates: primates, colugos, tree shrews, rodents, and rabbits	100
Grandorder	Euarchonta	Primates, colugos, and tree shrews	99–80
Mirorder	Primatomorpha	Primates and colugos	79.6
Order	Primates	Primates / Plesiadapiformes	66
Suborder	Haplorrhini	"Dry-nosed" primates: tarsiers and monkeys	63
Infraorder	Simiiformes	monkeys	40
Parvorder	Catarrhini	"Downward-nosed" primates: apes and old-world monkeys	30
Superfamily	Hominoidea	Apes: great apes and lesser apes	22–20
Family	Hominidae	Great apes: humans, chimpanzees, gorillas and orangutans—the hominids	20–15
Subfamily	Homininae	Humans, chimpanzees, and gorillas	14–12
Tribe	Hominini	Includes both Homo and Pan, but not Gorilla.	10–8
Subtribe	Hominina	Genus Homo and close human relatives and ancestors after splitting from Pan—the hominins	8–4
	Ardipithecus s.l.		6-4
	Australopithecus		3
Genus	Homo	Humans	2.5
	H. erectus s.l.
	H. heidelbergensis s.l.
Species	Homo sapiens ''s.s.''	Anatomically modern humans	0.8–0.3

Timeline

Unicellular life

Animalia

Chordata

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.