Modern Humans Did Not Admix with Neanderthals during Their Range Expansion into Europe. The authors seem to be using a demic diffusion model and suggest that the likelihood of Neanderthal mtDNA linages being eliminated through genetic drift alone is rather low.¹ Even assuming a low rate of admixture, a population expansion out of the Southwest Asia of "modern humans" into a Europe dominated by Neanderthals would still result in the persistence of a substantial portion of the latter's genome. Remember that the range expansion of modern culture might be carried out by individuals who were progressively more admixed with Neanderthal stock (assuming interfertility). This sort of process was highlighted by Cavalli-Sforza when he rejected Bryan Sykes' claim that Neolithic demic diffusion did not occur in Europe after the rise of agriculture in the Middle East because the NRY and mtDNA sources seem to be pointing to figures of about ~25% for "non-Paleolithic" ancestry in modern Europeans. Cavalli-Sforza replied that of course there would be a diminishment of Middle Eastern ancestry as the population expanded into Europe, but that did not imply that change was purely cultural, rather, the character of the demes changed (they became more "native" because of admixture each generation).

In any case, the conclusions in the article above shouldn't be that surprising, Out-of-Africa always seemed to be on strongest ground in the European case. Not only do the geneticists tend to favor Out-of-Africa (replacement), skull & bones paleontologists like Chris Stringer based the model in particular using the replacement of H. neanderthalis in Europe as a case study. Of course, this European case does not mean that I retract my contention that things are rather unsettled in paleoanthropology at the moment (the authors of the paper alluded to the possibility of mtDNA selective sweep, but only to dismiss it), we may find that rather than a unitary model we might have to simply live with regional explanations.

(via Dienekes)

1 - Retrieved Neanderthal and Paleolithic H. sapien mtDNA seems to point to the likelihood that no mtDNA from the former has persisted into modern populations.