Human evolution: eight million years, a bush of species

The most famous image of human evolution is wrong. That procession of silhouettes from stooped chimpanzee to upright human, the "march of progress", implies a linear succession, a steady improvement as each upgraded species replaces the last. The reality, as fossils accumulated over one hundred and fifty years make clear, looks far more like a bush than a ladder: dozens of species appear, coexist, interbreed and vanish across eight million years, none of them "on the way" to us¹.

This timeline begins seven million years ago with a skull found in the Chadian desert and ends today with a single surviving species, ours. In between: at least five major groups, around thirty recognised species, and as many open questions. Here is what fossils and genetics have taught us.

The earliest hominins: the dawn of bipedalismBipedalismA mode of locomotion on two hind limbs, the defining trait of the human lineage, appearing over 7 million years ago. Visible in the anatomy of the pelvis, femur and foramen magnum.→ (−8 to −4 Ma)

The split between the human lineage and that of chimpanzees is estimated, from genetic models, at between 6 and 8 million years ago. Into this window falls the oldest known homininHomininMember of the subtribe Hominina, comprising the human lineage (Homo, Australopithecus, Paranthropus…) but excluding orangutans and gibbons. The term progressively replaces "hominid" in its narrow sense.→: Sahelanthropus tchadensis, nicknamed Toumaï ("hope of life" in the Goran language), discovered in 2001 by Michel Brunet's team in the Toros-Ménalla region of Chad. Its skull, dated to roughly 7 million years ago, has a brain volume still very close to that of great apes (~360 cm³), but its foramen magnumForamen magnumThe opening at the base of the skull through which the spinal cord connects to the brain. Its position (rear → forward) is a bipedalism indicator: placed beneath the skull in bipeds, at the rear in quadrupeds.→, the opening through which the spinal column meets the skull, is positioned forward, indicating an upright posture. Studies published in 2022 on limb bones confirmed it walked bipedally, at least occasionally¹.

Slightly younger, Orrorin tugenensis (−6 Ma, Kenya) is known from a few teeth and bone fragments; its femur also suggests bipedalism. Ardipithecus kadabba (−5.8 to −5.2 Ma, Ethiopia) and Ardipithecus ramidus (−4.4 Ma, Ethiopia) complete the group. Ardi, the nickname given to the most complete A. ramidus specimen, a partial female skeleton from Aramis, profoundly changed our vision of bipedalism's origins. She walked upright on the ground but retained an opposable big toe for tree-climbing. The human–chimpanzee common ancestor therefore did not resemble a modern chimpanzee: it was already different, adapted to a mixed forest–savanna environment².

The australopithecines: African diversification (−4 to −2 Ma)

Between 4 and 2 million years ago, eastern and southern AfricaAfricaThe cradle of humankind: the continent where the first hominins appeared, then Homo sapiens around 300,000 years ago, before the expansion to the rest of the world.→ saw the proliferation of bipedal hominins with still-modest brains (400–550 cm³) but highly diverse adaptations: the australopithecines. This is not a single species but a bush of at least eight recognised species.

Australopithecus anamensis (−4.2 to −3.8 Ma) is among the oldest, with confirmed bipedalism readable in the tibia's structure. Its probable successor, Australopithecus afarensis (−3.9 to −2.9 Ma), is the group's best-known species thanks to Lucy, a partial female skeleton discovered in 1974 by Donald Johanson at Hadar, Ethiopia. With 40% of her bones preserved, Lucy long remained the most complete hominin fossil for such antiquity. She stood about 1.10 m, weighed 25–30 kg, walked upright but retained long arms and curved fingers suggesting a partially arboreal life².

Discoveries have multiplied since. Australopithecus africanus (−3.3 to −2.1 Ma, South Africa), the species of the Taung Child, discovered in 1924 by Raymond Dart, had a slightly larger brain. Australopithecus deyiremeda (−3.5 to −3.3 Ma, Ethiopia), described in 2015, coexisted with A. afarensis in the same Ethiopian corridor. Australopithecus bahrelghazali, found in Chad, extends the group's range to Central Africa. Australopithecus garhi (−2.5 Ma, Ethiopia) was found with animal bones bearing cut marks, possibly the earliest butchery. Australopithecus sediba (−1.98 Ma, South Africa), discovered by Lee Berger in 2008, shows features so close to Homo that some researchers regard it as a transitional species. Kenyanthropus platyops (−3.5 Ma, Kenya), with its flat, orthognathic face on an australopithecineAustralopithecineA genus of bipedal hominins from Africa (c. 4.2–1.9 Ma) with a brain still close to that of great apes (400–550 cm³) but walking upright. Lucy (<em>Au. afarensis</em>) is the most famous specimen.→-sized skull, stands apart and is sometimes linked to Homo rudolfensis³.

The Paranthropus: the robust branch (−2.7 to −1 Ma)

Around 2.7 million years ago, one branch of australopithecines took a radically different evolutionary path: the Paranthropus, or "robust hominins". Their skulls are recognisable by their sagittal crest (a bony ridge along the top of the skull anchoring chewing muscles), flared cheekbones and enormous rear teeth, adaptations to a tough diet of tubers, seeds and fibrous roots.

Paranthropus aethiopicus (−2.7 to −2.3 Ma), known notably by the "Black Skull" (KNM-WT 17000), is the oldest. Paranthropus boisei (−2.4 to −1.4 Ma, East Africa), nicknamed "Nutcracker Man" by Louis Leakey who found it in 1959, had the largest molars of any hominin, four times wider than ours. Paranthropus robustus (−2 to −1 Ma, South Africa) shared caves with early Homo representatives, proving two very different hominin cousins coexisted in the same territory for hundreds of thousands of years. The Paranthropus lineage vanished without known descendants¹.

The emergence of genus Homo (−2.8 Ma)

The boundary between australopithecines and genus Homo is not sharp, it is precisely what is constantly debated. Current convention places the appearance of Homo at around 2.8 million years ago, with Homo habilis (−2.4 to −1.4 Ma) and its contemporary Homo rudolfensis (−2.5 to −1.5 Ma). Both had slightly larger brains (550–750 cm³) and are associated with the first systematic stone tool industries: the OldowanOldowanThe oldest known stone-tool industry (c. 3.3–1.7 Ma), characterised by flaked pebbles (choppers) and basic flakes. Named after Olduvai Gorge (Tanzania).→, from Olduvai Gorge in Tanzania, which yields the oldest deliberately knapped pebbles (~2.6 Ma).

Homo ergaster (−1.9 to −1.4 Ma, East Africa) represents a major anatomical leap: longer legs, a more slender body, a larger brain (800–900 cm³) and command of a more refined stone-tool technology, the AcheuleanAcheuleanA stone-tool industry (c. 1.7 Ma–300,000 BP) characterised by large, finely worked almond-shaped bifaces. Associated with Homo ergaster and erectus and spread from Africa to Europe and Asia.→, characterised by large almond-shaped bifaces. It is probably Homo ergaster, or a closely related population, that first crossed the African frontier³.

Homo erectus: the great traveller (−2 to −0.1 Ma)

Homo erectus is the most enduring human species in history: it persists for nearly two million years, from Africa to South-East Asia. The site of Dmanisi in Georgia yielded fossils dated to 1.85 Ma, the oldest known hominins outside Africa. These Dmanisi hominins had relatively small brains (600–700 cm³), suggesting that the exit from Africa occurred early, before full cerebral development. A 2025 study proposed that the Dmanisi fossils might belong to two distinct species, Homo georgicus and Homo caucasi, implying multiple human species left Africa together as early as 1.8 Ma³.

In Asia, Homo erectus leaves remarkable traces: Peking Man (Zhoukoudian, China, −780,000 to −230,000) and Java Man (Indonesia, −1.5 Ma to −100,000). Some island populations may have given rise, through insular dwarfismInsular dwarfismReduction in the body size of an animal species due to island isolation, where resources are limited and predators absent. Explains the small stature of Homo floresiensis.→, to Homo floresiensis on Flores.

Old World diversification (−1 Ma to −300,000 years)

Homo antecessor (−1.2 to −0.8 Ma, Spain), discovered at AtapuercaAtapuercaA complex of archaeological sites in the Sierra de Atapuerca (Burgos, Spain), a UNESCO site, yielding an exceptional sequence of human fossils, including the Sima de los Huesos and Homo antecessor.→ in 1994, is the oldest known European. Its features, a modern face paired with a prominent brow ridge, make it a possible common ancestor of Neanderthals and Homo sapiensHomo sapiensThe present-day human species, which emerged in Africa around 300,000 years ago, the only surviving human lineage after the extinction of Neanderthals and Denisovans.→. Homo heidelbergensis (−600,000 to −250,000, Europe and Africa), robustly built and tall, was the first to systematically hunt large game and build shelters. It is widely regarded as the probable ancestor of Neanderthals in Europe and Homo sapiens in Africa².

Homo luzonensis (−67,000 to −50,000, Philippines), described in 2019 from thirteen fossils in Callao Cave, presents a baffling mosaic of primitive and modern features. Homo naledi, found in 2013 in Rising Star Cave (South Africa) by Lee Berger, had a tiny brain (~460 cm³), yet lived far more recently than its anatomy implies: dating yields −335,000 to −236,000 years, making it contemporary with early Homo sapiens. The deliberate deposition of its bones in inaccessible chambers raises the possibility of funerary behaviour in a small-brained species¹.

The last humanities: Neanderthals, Denisovans, Homo sapiens

Homo neanderthalensis (−400,000 to −40,000) and the Denisovans (genetically known since 2010, attested to roughly −500,000 to −30,000) are two sister lineages, both descended from African Homo heidelbergensis. Neanderthals colonised Europe and the Near EastNear EastA region of western Asia (Levant, Mesopotamia, Anatolia, Iran), cradle of the Neolithic revolution, agriculture, the first cities and writing.→; Denisovans occupied Central and East Asia. The Denisovans are known primarily not from bones but from DNA extracted from a finger bone in Denisova Cave, Siberia, a methodological revolution that launched the era of palaeogenomics.

Homo sapiens emerges in Africa around 300,000 years ago (Jebel Irhoud, Morocco) and expands out of Africa around 70,000 years ago. During this expansion, it encounters and interbreeds with Neanderthals and Denisovans: all living non-African humans carry 1–4% Neanderthal DNA; some Melanesian and Papuan populations carry up to 6% DenisovanDenisovanAn extinct human population, cousin of the Neanderthals, identified in 2010 from the DNA of remains in Denisova Cave (Siberia).→ DNA. These genetic traces are irrefutable proof of fertile encounters between lineages that bone morphology alone would classify as distinct species².

Coexistences, extinctions, hybridisations

One of the chart's major lessons is that coexistence between human species was not the exception but the rule. Paranthropus and Homo shared the same African valleys for over a million years. Homo sapiens, Neanderthals, Denisovans, Homo floresiensis and Homo luzonensis all overlapped in time between 100,000 and 40,000 years ago. As recently as 50,000 years ago, Earth was home to at least four or five distinct human species. Their progressive disappearance coincides with the expansion of Homo sapiens, though the exact causes, competition, genetic absorption, climatic shifts, remain debated.

PalaeogeneticsPalaeogeneticsThe study of ancient DNA extracted from remains (bones, teeth, sediments, walls) to reconstruct the past of populations.→ has shown that these extinctions were rarely clean replacements: they were often partial absorptions. The genome of every living human outside Africa is a palimpsest, bearing traces of encounters with at least two other species. Denisovan DNA gave Tibetans the EPAS1 variant enabling high-altitude life; Neanderthal DNA contributes to our immune response. These genetic borrowings are not curiosities, they testify to a profoundly hybrid biology³.

What 2025 changed

PalaeoanthropologyPalaeoanthropologyThe science that studies human evolution from the fossil remains of hominins (bones, teeth, footprints) and their context, to reconstruct our biological origins.→ never stops renewing itself. In 2025, excavations in Ethiopia uncovered new fossils showing that Australopithecus and the earliest Homo coexisted at the same location 2.6–2.8 million years ago. The same year, reanalysis of Dmanisi fossils suggested two species, not one, made the first exit from Africa. In December 2025, the digital reconstruction of a 1.5-million-year-old Ethiopian Homo erectus face revealed a more primitive morphology than expected, blurring the boundary between ergaster and erectus once more.

The message of contemporary research is consistent: the deeper we dig, the bushier the tree. The human lineage is not a highway but a delta, a network of channels that branch, reconverge, disappear or reach the sea. We are the only channel that made it to the present.