The main orientations of human genetic differentiation

For the past couple of weeks I've been running experiments with SPatial Ancestry analysis (SPA) software, trying to design model files that place personal genomics customers as close as possible to their geographic points of origin on a Google map. It's proving a bit of a headache, largely because I'm finding it difficult to get the longitude right for everyone, especially for samples from across Northern Europe. In comparison, the latitude results almost take care of themselves. The abstract below, from the recent ASHG 2012 conference, explains why..

Anisotropic isolation by distance: the main orientations of human genetic differentiation. F. Jay1,2, P. Sjödin3, M. Jakobsson3,4, M. G. B. Blum2 1) Laboratoire TIMC-IMAG UMR 5525, Université Joseph Fourier, Centre National de la Recherche Scientifique, Grenoble, France; 2) Department of Integrative Biology, UC Berkeley, Berkeley, CA; 3) Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden; 4) Science for Life Laboratory, Uppsala University, Uppsala, Sweden.

Genetic differentiation among human populations is greatly influenced by geography due to the accumulation of local allele frequency differences. However, little is known about the possibly different increment of genetic differentiation along the different directions (north-south, east-west, ...). We analyzed genome-wide polymorphism data from African (n=29), Asiatic (n=26), Native American (n=9) and European (n=38) populations, and we found that the major orientations of genetic differentiation are north-south in Europe and Africa, east-west in Asia, but no preferential orientation was found in the Americas. A practical consequence of the anisotropic pattern of genetic differentiation is that the localization of an individual's geographic origin based on SNP data should be more precise along the orientation of maximum differentiation. We compared the localization of geographic origin obtained with principal component regression with a baseline method and confirmed that the largest improvement was obtained along the orientation of maximum differentiation. Our findings have implications for interpreting the making of human genetic variation in terms of isolation by distance and spatial range expansion processes

Update 8/12/2012: the full study is now out, and well worth a read (see here). But someone should remove that Slovakian individual from the POPRES dataset. This person clearly has exotic ancestry.

Jay et al., Anisotropic isolation by distance: the main orientations of human genetic differentiation, Mol Biol Evol (2012) doi: 10.1093/molbev/mss259 First published online: November 20, 2012