…we measured allele frequency differentiation among Europeans, Chinese and Africans for 24 human pigmentation genes from 2 publicly available, large scale SNP data sets. Several skin pigmentation genes show unusually large allele frequency differences among these populations. To determine whether these allele frequency differences might be due to selection, we employed a within-population test based on long-range haplotype structure and identified several outliers that have not been previously identified as putatively adaptive. Most notably, we identify the DCT gene as a candidate for recent positive selection in the Chinese. Moreover, our analyses suggest that it is likely that different genes are responsible for the lighter skin pigmentation found in different non-African populations.
There are many posts about skin color in the GNXP archives. This should not surprise. The fact that SLC24A5 was positively selected for in Europeans and correlates with light skin, but remains ancestral in both Africans and East Asians, while the Arg163Gln variant of MC1R seems under selection in East Asians, but under relaxed selection or possibly diversifying selection in Europeans suggests that different genetic strategies are scaling the same phenotypic fitness landscape. Additionally, two different strategies suggests to me that gene flow has been low enough so that one best case strategy (i.e., the highest fitness peak in a large admixing population) isn’t automatically selected across Eurasia across the common genetic background. You know what they say, selection is stochastic….