Recent African origin of modern humans

Successive dispersals of      Homo erectus (yellow),      Homo neanderthalensis (ochre) and      Homo sapiens (red).
Expansion of early modern humans from Africa through the Near East
Map of the migration of modern humans out of Africa, based on mitochondrial DNA. Colored rings indicate thousand years before present.

In paleoanthropology, the recent African origin of modern humans, also called the "Out of Africa" theory (OOA), recent single-origin hypothesis (RSOH), replacement hypothesis, or recent African origin model (RAO), is the dominant[1][2][3] model of the geographic origin and early migration of anatomically modern humans (Homo sapiens). It follows the early expansions of hominins out of Africa, accomplished by Homo erectus and then Homo neanderthalensis.

The model proposes a "single origin" of Homo sapiens in the taxonomic sense, precluding parallel evolution of traits considered anatomically modern in other regions,[4] but not precluding multiple admixture between H. sapiens and archaic humans in Europe and Asia.[note 1][5][6]H. sapiens most likely developed in the Horn of Africa between 300,000 and 200,000 years ago.[7][8] The "recent African origin" model proposes that all modern non-African populations are substantially descended from populations of H. sapiens that left Africa after that time.

There were at least several "out-of-Africa" dispersals of modern humans, possibly beginning as early as 270,000 years ago, including 215,000 years ago to at least Greece,[9][10][11] and certainly via northern Africa about 130,000 to 115,000 years ago.[12][13][14][15][16][17] These early waves appear to have mostly died out or retreated by 80,000 years ago.[18]

The most significant "recent" wave took place about 70,000–50,000 years ago,[7][8][19][20][21] via the so-called "Southern Route", spreading rapidly along the coast of Asia and reaching Australia by around 65,000–50,000 years ago,[22][23][note 2] (though some researchers question the earlier Australian dates and place the arrival of humans there at 50,000 years ago at earliest,[24][25] while others have suggested that these first settlers of Australia may represent an older wave before the more significant out of Africa migration and thus not necessarily be ancestral to the region's later inhabitants[21]) while Europe was populated by an early offshoot which settled the Near East and Europe less than 55,000 years ago.[26][27][28]

In the 2010s, studies in population genetics have uncovered evidence of interbreeding that occurred between H. sapiens and archaic humans in Eurasia and Oceania but not in Africa,[29] which means that all non-African modern population groups, while mostly derived from early H. sapiens, are to a lesser extent also descended from regional variants of archaic humans.

Proposed waves

See Early hominin expansions out of Africa for archaic humans (H. erectus, H. heidelbergensis, Neanderthals, Denisovans).
Layer sequence at Ksar Akil in the Levantine corridor, and discovery of two fossils of Homo sapiens, dated to 40,800 to 39,200 years BP for "Egbert",[30] and 42,400–41,700 BP for "Ethelruda".[30].

"Recent African origin," or Out of Africa II, refers to the migration of anatomically modern humans (Homo sapiens) out of Africa after their emergence at c. 300,000 to 200,000 years ago, in contrast to "Out of Africa I", which refers to the migration of archaic humans from Africa to Eurasia roughly 1.8 to 0.5 million years ago.

Since the beginning of the 21st century, the picture of "recent single-origin" migrations has become significantly more complex, not only due to the discovery of modern-archaic admixture but also due to the increasing evidence that the "recent out-of-Africa" migration took place in a number of waves spread over a long time period. As of 2010, there were two main accepted dispersal routes for the out-of-Africa migration of early anatomically modern humans: via the "Northern Route" (via Nile Valley and Sinai) and the "Southern Route" via the Bab al Mandab strait.[31]

  • Posth et al. (2017) suggest that early Homo sapiens, or "another species in Africa closely related to us," might have first migrated out of Africa around 270,000 years ago.[32]
  • Finds at Misliya cave, which include a partial jawbone with eight teeth, have been dated to around 185,000 years ago. Layers dating from between 250,000 and 140,000 years ago in the same cave contained tools of the Levallois type which could put the date of the first migration even earlier if the tools can be associated with the modern human jawbone finds.[33][34]
  • An Eastward Dispersal from Northeast Africa to Arabia 150,000–130,000  years ago based on the finds at Jebel Faya dated to 127,000 years ago (discovered in 2011).[12][13] Possibly related to this wave are the finds from Zhirendong cave, Southern China, dated to more than 100,000 years ago.[31] Other evidence of modern human presence in China has been dated to 80,000 years ago.[18]
  • The most significant dispersal took place around 50–70,000 years ago via the so-called Southern Route, either before[35] or after[27][28] the Toba event, which happened between 69,000 and 77,000 years ago.[35] This dispersal followed the southern coastline of Asia, and reached Australia around 65,000-50,000 years ago, or according to some research, by 50,000 years ago at earliest[24][36]. Western Asia was "re-occupied" by a different derivation from this wave around 50,000 years ago, and Europe was populated from Western Asia beginning around 43,000 years ago.[31]
  • Wells (2003) describes an additional wave of migration after the southern coastal route, namely a northern migration into Europe at circa 45,000 years ago.[note 3] However, this possibility is ruled out by Macaulay et al. (2005) and Posth et al. (2016), who argue for a single coastal dispersal, with an early offshoot into Europe.