Recent African origin of modern humans

The recent African origin of modern humans or the "Out of Africa" theory (OOA) holds that present-day humans outside Africa descend mainly from a single expansion of anatomically modern humans (Homo sapiens) from Africa about 70,000–50,000 years ago. It is the most widely accepted paleo-anthropological model of the geographic origin and early migration of the human species. This expansion follows the earlier 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 in other regions of traits considered anatomically modern, but not precluding multiple admixture between H. sapiens and archaic humans in Europe and Asia. H. sapiens most likely developed in Africa between 300,000 and 200,000 years ago, with one hypothesis arguing that diverse morphological features of H. sapiens appeared locally in different parts of Africa and converged due to gene flow between different populations within the same period. 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, certainly via North Africa and the Arabian Peninsula about 130,000 to 115,000 years ago at least. There is evidence that modern humans had reached China around 80,000 years ago. Practically all of these early waves seem to have gone extinct or retreated back, and present-day humans outside Africa descend mainly from a single expansion about 70,000–50,000 years ago, via the so-called "Southern Route". These humans spread rapidly along the coast of Asia and reached Australia by around 65,000–50,000 years ago, (though some researchers question the earlier Australian dates and place the arrival of humans there at 50,000 years ago at earliest, 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) while Europe was populated by an early offshoot which settled the Near East and Europe less than 55,000 years ago. In the 2010s, studies in population genetics uncovered evidence of interbreeding that occurred between H. sapiens and archaic humans in Eurasia, Oceania and Africa, indicating that 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

"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 from before 1.8 and up to 0.5 million years ago. Omo-Kibish I (Omo I) from southern Ethiopia is the oldest anatomically modern Homo sapiens skeleton currently known (around 233,000 years old). There are even older Homo sapiens fossils from Jebel Irhoud in Morocco which exhibit a mixture of modern and archaic features at around 315,000 years old. Since the beginning of the 21st century, the picture of "recent single-origin" migrations has become significantly more complex, due to the discovery of modern-archaic admixture and the increasing evidence that the "recent out-of-Africa" migration took place in waves over a long time. As of 2010, there were two main accepted dispersal routes for the out-of-Africa migration of early anatomically modern humans, the "Northern Route" (via Nile Valley and Sinai) and the "Southern Route" via the Bab-el-Mandeb strait.

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 based on the closer affinity within Neanderthals' mitochondrial genomes to Homo sapiens than Denisovans. An interpretation, with as of yet limited recognition, of a skull fragment coming from Apidima Cave in Greece dated at 210,000 years ago as a Homo sapiens specimen may also points to an early Homo sapiens migration. Finds at Misliya cave, which include a partial jawbone with eight teeth, that may belong to a Homo sapiens specimen, 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. An eastward dispersal from Northeast Africa to Arabia 150,000–130,000 years ago is based on the stone tools finds at Jebel Faya dated to 127,000 years ago (discovered in 2011), although fossil evidence in the area is significantly later at 85,000 years ago. Possibly related to this wave are the finds from Zhirendong cave, Southern China, dated to more than 100,000 years ago. Other evidence of modern human presence in China has been dated to 80,000 years ago. The most significant out of Africa dispersal took place around 50,000–70,000 years ago via the so-called Southern Route, either before or after the Toba event, which happened between 69,000 and 77,000 years ago. 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. 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. Wells (2003) describes an additional wave of migration after the southern coastal route, a northern migration into Europe about 45,000 years ago. 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.

Northern Route dispersal

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