Paleolithic

Anatomically modern humans evolved from archaic Homo sapiens in Africa in the Middle Paleolithic, about 200,000 years ago. By the beginning of the Upper Paleolithic 50,000 BP (Before Present), full behavioral modernity, including language, music and other cultural universals had developed.

The out of Africa migration is estimated to have occurred about 70,000 years BP. Modern humans subsequently spread to all continents, replacing earlier hominids: they inhabited Eurasia and Oceania by 40,000 BP, and the Americas at least 14,500 years BP. A popular theory is that they displaced Homo neanderthalensis and other species descended from Homo erectus (which had inhabited Eurasia as early as 2 million years ago) through more successful reproduction and competition forresources. The exact manner or extent of the coexistence and interaction of these species is unknown and remains a controversial subject.

Evidence from archaeogenetics accumulating since the 1990s has lent strong support to the "out-of-Africa" scenario, and has marginalized the competing multiregional hypothesis, which proposed that modern humans evolved, at least in part, from independent hominid populations.

Geneticists Lynn Jorde and Henry Harpending of theUniversity of Utah propose that the variation in human DNA is minute compared to that of other species. They also propose that during the Late Pleistocen, the human population was reduced to a small number of breeding pairs– no more than 10,000, and possibly as few as 1,000 - resulting in a very small residual gene pool. Various reasons for this hypothetical bottleneck have been postulated, one being the Toba catastrophe theory.