Human-on-human sex

Dienekes tips me off to the fact that the long-awaited Reich lab paper on Neandertal admixture dating has finally been put on arXiv! The date of interbreeding between Neandertals and modern humans:

Comparisons of DNA sequences between Neandertals and present-day humans have shown that Neandertals share more genetic variants with non-Africans than with Africans. This could be due to interbreeding between Neandertals and modern humans when the two groups met subsequent to the emergence of modern humans outside Africa. However, it could also be due to population structure that antedates the origin of Neandertal ancestors in Africa. We measure the extent of linkage disequilibrium (LD) in the genomes of present-day Europeans and find that the last gene flow from Neandertals (or their relatives) into Europeans likely occurred 37,000-86,000 years before the present (BP), and most likely 47,000-65,000 years ago. This supports the recent interbreeding hypothesis, and suggests that interbreeding may have occurred when modern humans carrying Upper Paleolithic technologies encountered Neandertals as they expanded out of Africa.

This isn’t the only group working on the Neandertal genomic admixture story. From reading his blog you probably know that John Hawks is working in this area, but there are other labs too. I’m hoping that the Reich lab pushing their stuff on arXiv will prompt the other groups to also start moving (instead of just presenting preliminary results to a narrow group of researchers).

As for these results, I’m still amazed that LD based methods can work this far into the deep past. Second, it is nice that the low bound estimate can plausibly predate the arrival of anatomically modern humans to Australia. Also, this admixture date is well after anatomical modern humanity, and well before the classical “Great Leap Forward” of behavioral modernity. Though I think that over the next few years we may start to discard the idea of any such punctuated leap.

And again, it’s on arXiv. As they used to say, read the whole thing!

Source: Discover Magazine – Gene Expression