Saturday, September 03, 2005

Neandertal days....   posted by Razib @ 9/03/2005 12:52:00 AM

Dienekes has extensive commentary on a paper that seems to end by leaning toward a predominant Out-of-Africa replacement model for the emergence of modern humans and the transition between Neandertals and our species in Europe. Their method was to use simulations where they tweaked the parameters of the period of transition between the two groups and the effective population size fluctuations of humans. Here is their conclusion:
The significance of ancient Neandertal mtDNA for resolving the fate of Neandertals increases greatly when considered in light of models for modern human origins derived from archaeology. On the basis of mtDNA, if Neandertals survived late in Europe, their per generation contribution to early modern human populations must have been fairly small (<0.2%) or we would find Neandertal mtDNA lineages in living humans. If the human population size remained constant and small until very recently, then the total, accumulated Neandertal admixture could still have been large, but if the human population started to grow rapidly from a small size about 40,000 years ago, then even a very small Neandertal genetic contribution to modern human populations can be ruled out. Archaeology tends to support the rapid population growth model (Klein et al. 2004, Stiner et al. 1999), as does living human mtDNA (Excoffier and Schneider 1999, Ingman et al. 2000). Other genetic regions are more equivocal about the timing and magnitude of population growth (Harpending and Rogers 2000, Ptak and Przeworski 2002, Wall and Przeworski 2000), but recent studies of SNPs and microsatellites appear to be reaching a consensus consistent with the results for mtDNA (Marth et al. 2004, Zhivotovsky, Rosenberg, and Feldman 2003). Our results stress the importance of fully integrating archaeological, fossil, and genetic evidence in investigations of modern human origins.