Sriram Sankararaman, Nick Patterson, Heng Li, Svante Pääbo and David Reich have a new paper (open access, via ArXiv here) that tests whether or not genetic similarities between recent humans and Neandertals is the result of recent admixture or ancient population structure. This is an important paper and one that I will write more on later, but for now I will just send along the link.
The date of 37,000-86,000 years BP is too recent to be consistent with the “ancient African population structure” scenario, and strongly supports the hypothesis that at least some of the signal of Neandertals being more closely related to non-Africans than to Africans is due to recent gene flow. These results are concordant with a recent paper by Yang et al [44] that analyzed joint allele frequency spectra, to reject the ancient structure scenario.
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1. Sriram Sankararaman, Nick Patterson, Heng Li, Svante Pääbo, David Reich (2012) The date of interbreeding between Neandertals and modern humans. arXiv:1208.2238v1