Models of modern human origins. In each case, anatomically modern humans are designated in blue and Neanderthals (and other extinct Eurasian archaic human species) in red. The gray root indicates the common origin of all human species, most probably in Africa. (a) The 'African replacement' hypothesis proposes that anatomically modern humans originated in Africa, expanding into Eurasia relatively recently and replacing other human species, such as the Neanderthals, which had evolved independently there [1,2]. (b) In contrast, an older hypothesis, the 'multiregional model', envisages that the evolution of modern humans occurred in both Africa and Eurasia, maintaining local genetic continuity but with populations united by gene flow [3-6]. (c) Some researchers combine these models, seeing a recent African origin for the bulk of the human genome, but limited admixture with existing populations .
Hodgson and Disotell Genome Biology 2008 9:206 doi:10.1186/gb-2008-9-2-206