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 our species.

This expansion 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 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 the Horn of Africa between 300,000 and 200,000 years ago, although an alternative hypothesis argues 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 northern 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,^{[excessive citations]} 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.

"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.

Beginning 135,000 years ago, tropical Africa experienced megadroughts which drove humans from the land and towards the sea shores, and forced them to cross over to other continents.