Abstract
BackgroundAnthropological and genetic data agree in indicating the African continent as the main place of origin for anatomically modern humans. However, it is unclear whether early modern humans left Africa through a single, major process, dispersing simultaneously over Asia and Europe, or in two main waves, first through the Arab Peninsula into southern Asia and Oceania, and later through a northern route crossing the Levant.ResultsHere, we show that accurate genomic estimates of the divergence times between European and African populations are more recent than those between Australo-Melanesia and Africa and incompatible with the effects of a single dispersal. This difference cannot possibly be accounted for by the effects of either hybridization with archaic human forms in Australo-Melanesia or back migration from Europe into Africa. Furthermore, in several populations of Asia we found evidence for relatively recent genetic admixture events, which could have obscured the signatures of the earliest processes.ConclusionsWe conclude that the hypothesis of a single major human dispersal from Africa appears hardly compatible with the observed historical and geographical patterns of genome diversity and that Australo-Melanesian populations seem still to retain a genomic signature of a more ancient divergence from AfricaElectronic supplementary materialThe online version of this article (doi:10.1186/s13323-015-0030-2) contains supplementary material, which is available to authorized users.
Highlights
Anthropological and genetic data agree in indicating the African continent as the main place of origin for anatomically modern humans
Genetic relationships largely correspond to geographical distances, with Eurasian populations separated from the African ones along the axis represented by PC1, and forming an orderly longitudinal cline, all the way from Europe to East Asia and Oceania, along the PC2 axis
At k = 2, the ancestry assignment differentiated between African and non-African populations; k = 3 further distinguishes Europeans from Asians; k = 4 identifies an AustraloMelanesian component within the Asian cluster; at k = 5, the additional component is mainly associated with the Indian subcontinent; the same is the case at k = 6 for Polynesia and Fiji and at k = 7 for many island communities of Southeast Asia and Oceania
Summary
Anthropological and genetic data agree in indicating the African continent as the main place of origin for anatomically modern humans. It is unclear whether early modern humans left Africa through a single, major process, dispersing simultaneously over Asia and Europe, or in two main waves, first through the Arab Peninsula into southern Asia and Oceania, and later through a northern route crossing the Levant. Morphologic [12, 13], archaeological [14], and genetic [13, 15,16,17,18,19,20] evidence suggest that part of the AMH population might have dispersed before that date, possibly by a Southern route into southern Asia through the horn of Africa and the Arab Peninsula
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