I don’t recall where I found this recent paper by David Serre and Svante Pääbo, so my apologies if it has already been linked to.
Here’s the abstract:
Evidence for Gradients of Human Genetic Diversity Within and Among ContinentsGenetic variation in humans is sometimes described as being discontinuous among continents or among groups of individuals, and by some this has been interpreted as genetic support for “races.” A recent study in which >350 microsatellites were studied in a global sample of humans showed that they could be grouped according to their continental origin, and this was widely interpreted as evidence for a discrete distribution of human genetic diversity. Here, we investigate how study design can influence such conclusions. Our results show that when individuals are sampled homogeneously from around the globe, the pattern seen is one of gradients of allele frequencies that extend over the entire world, rather than discrete clusters. Therefore, there is no reason to assume that major genetic discontinuities exist between different continents or “races.”
The full paper is published in Genome Research, 14:1679-1685, 2004. A pdf may be available here.
Apart from the findings of substance, the paper raises important issues of methodology: in particular, the choice of sampling frame and statistical inference procedures.
I’m not qualified to judge the technical issues, but presumably the authors’ approach is not obviously wrong, or the paper would not have passed peer review. My only thought is that if the aim is to infer patterns of human genetic history before, say, the last 3,000 years, then the choice of samples should not be influenced by present-day patterns of population density, since these are the result of post-Neolithic population changes.
Posted by David B at 04:01 AM