I’ll hopefully have more time to write about this tomorrow, but for now I’ll simply suggest that you go and read the free full text PDF of this advance online manuscript in Genome Research.
This is the most important recent paper in the field of human evolutionary genetics – a thorough and careful analysis of the signatures of positive natural selection left in our genome by the last 10-40,000 years of adaptation, using a population sample that is far broader than those used in previous studies (53 populations rather than 4). I covered some of the approaches used in the paper in this post on the HGDP Selection Bowser, which is a graphical window into the same data used in this study.
Further exploration of the geographic patterns in these data and their implications is warranted, but from the point of view of identifying candidate loci for functional verification, the fact that putatively selected loci often conform to the geographic patterns characteristic of neutral loci is somewhat worrying. This suggests that distinguishing true cases of selection from the tails of the neutral distribution may be more difficult than sometimes assumed, and raises the possibility that many loci identified as being under selection in genome scans of this kind may be false positives. Reports of ubiquitous strong (s = 1-5%) positive selection in the human genome (Hawks et al. 2007) may be considerably overstated. [my emphasis]
Hawks et al. 2007 refers to this paper on the “recent acceleration” hypothesis of human evolution, championed by anthropologist blogger John Hawks and expanded on by Gregory Cochran and Henry Harpending in their recent book The 10000 Year Explosion. To my knowledge this is the first direct challenge to Hawks’ hypothesis in the peer-reviewed literature; it will be interesting to see how this discussion develops.