Statistical evaluation of alternative models of human evolution:
An appropriate model of recent human evolution is not only important^ to understand our own history, but it is necessary to disentangle^ the effects of demography and selection on genome diversity.^ Although most genetic data support the view that our species^ originated recently in Africa, it is still unclear if it completely^ replaced former members of the Homo genus, or if some interbreeding^ occurred during its range expansion. Several scenarios of modern^ human evolution have been proposed on the basis of molecular^ and paleontological data, but their likelihood has never been^ statistically assessed. Using DNA data from 50 nuclear loci^ sequenced in African, Asian and Native American samples, we^ show here by extensive simulations that a simple African replacement^ model with exponential growth has a higher probability (78%)^ as compared with alternative multiregional evolution or assimilation^ scenarios. A Bayesian analysis of the data under this best supported^ model points to an origin of our species ~141 thousand years^ ago (Kya), an exit out-of-Africa ~51 Kya, and a recent colonization^ of the Americas ~10.5 Kya. We also find that the
African replacement^ model explains not only the shallow ancestry of mtDNA or Y-chromosomes^ but also the occurrence of deep lineages at some autosomal loci,^ which has been formerly interpreted as a sign of interbreeding
^ with Homo erectus.
I don't have time to read this paper now, so I hope John Hawks blogs it soon. Obviously I'm curious as to how they explain deep lineages, Bruce Lahn's Neandertal introgression paper attempted to check for dynamics such as balancing selection.
