The plot below shows the first two principal components of genetic variation among nationals across the globe. I gather that this is based on a larger and more diverse sample than hitherto possible although it still seems small to me (N=850). The first (and dominant) dimension appears to be mostly a gap between Africa and the rest, whereas the second dimension runs from East Asia to Europe. I have long wondered when this sort of data would become available. I have to admit that I am a bit fearful of what social scientists are going to do with it (or perhaps people already have?). Surely, you can dump this in one of our cross-national datasets and something significant will show up in a regression analysis. I just hope that the first users and reviewers of this data are going to be the type of cautious and intellectually curious scholars this type of data requires. Co-authoring with natural scientists also sounds like a good idea to me.
The graph is from a forthcoming article in Genomics. Much more detail, graphs, and fascinating analysis is at the Discover blog.
ps. See very helpful notes by James Fowler and Razib Khan in the comments.