Replacement theory

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, in paleoanthropology, the dominant model of the geographic origin and early migration of anatomically modern humans (Homo sapiens), which proposes a single area of origin for modern humans. According to this model, modern humans evolved in East Africa, and started to disperse through the world roughly 50,000 to 100,000 years ago. The single-origin hypothesis is cited as having the scientific consensus as of the mid-2000s.

The major competing hypothesis of "recent single origin" has been the multiregional origin of modern humans, which envisions a wave of Homo sapiens migrating earlier from Africa and interbreeding with local Homo erectus populations in multiple regions of the globe.

In the 2010s, the discovery of evidence of archaic admixture of modern humans outside of Africa with Neanderthals and Denisovans has complicated the picture. As of 2011, it appears likely that there were two waves of migration out of Africa. The first took place between 130,000–115,000 years ago via northern Africa, and appears to have mostly died out or retreated (although there is some evidence of a presence of modern humans in China about 80,000 years ago). A second dispersal took place via the so-called Southern Route, following the southern coastline of Asia, which led to the lasting colonization of Eurasia and Australia by around 50,000 years ago. Europe was populated by an early offshoot which settled the Near East and Europe (post-Toba hypothesis).

Anatomically modern humans originated in Africa by about 200,000 years ago. The trend in cranial expansion and the acheulean elaboration of stone tool technologies which occurred between 400,000 years ago and the second interglacial period in the Middle (around 250,000 years ago) provide evidence for a transition from Homo erectus to H. sapiens. In the Recent African Origin (RAO) scenario, migration within and out of Africa eventually replaced the earlier dispersed H. erectus.

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