Out of Africa and into Asia: Fossil and genetic evidence on modern human origins and dispersals

Genetic and fossil evidence has accumulated in support of an African origin for modern humans. Despite this consensus, several questions remain with regard to the mode and timing of dispersal out of the continent. Competing models differ primarily by the number of dispersals, their geographic route, and the extent to which expanding modern humans interacted with other hominins. Central in this debate is whether Southeast Asia was occupied significantly earlier than other parts of Eurasia and, if so, whether the population ancestral to extant Southeast Asians was notably different from the ancestors of extant Eurasians. Here, genetic and fossil evidence for the dispersal process out of Africa and into Asia is reviewed. A scenario that can resolve the current archaeological, genetic, and paleontological evidence is one which considers an initial expansion of anatomically modern humans into the Arabian Peninsula and the Levant during the terminal Middle Pleistocene, with continued exchange with Africans until the Late Pleistocene, when modern humans then dispersed into Eurasia in two waves. Advances in population genomics and methods applying evolutionary theory to the fossil record will serve to further clarify modern human origins and the out-of-Africa process.