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Monday, October 17, 2011

Pigmentation genetics of Europeans

The maps below are based on three genome-wide SNPs showing high correlation with blue and green eyes and/or fair hair in Europeans. The results obviously suggest that there's an increase in hair and eye blondism from south to north in Europe, with clear peaks east of the Baltic Sea. The three SNPs are rs1667394 (HERC2 gene), rs12913832 (OCA2 gene), and rs12896399 (SLC24A4 gene).

Indeed, I'm a bit taken aback by the very high rate of suggested blondism among the Belorussians and Mordvinians (second highest dot in Russia). This might have something to do with sampling bias. Perhaps most of the 12 Belorussians and 16 Mordvinians used here came from fairer than average communities within their respective nations? I have no idea. In any case, I don't think the picture is too far from reality, because multiple sampling sites from the same general biogeographic zones, but several hundred kilometers apart, are showing very similar results. This can't be a coincidence.

It's also interesting to note that the East Baltic peak in blondism genotypes correlates closely with the North + East European genome-wide ancestral component in my latest ADMIXTURE experiment (see here). Perhaps this is where natural selection for these traits was most extreme due to very specific environmental pressures, like lack of sunlight? Maybe this is also where these traits spread from, either gradually or during one or several major migrations? Someone should look into that. Meantime, I'll try and update this post with new maps as more samples come in.