Allele for light pigmentation has been positively selected in Europeans

Dienekes Pontikos:

A new paper shows that a polymorphism on the AIM1 locus which is associated with human pigmentation has been under strong positive selection in Europeans, reaching almost fixation in tested European populations (0.89 in South Africans and 0.96 in Germans), while being rare elsewhere. The derived allele is associated with lighter overall pigmentation. This contrasts to the situation with the MC1R locus in which the ancestral variant is maintained by selection in Negroids, but multiple unrelated mutations outside Africa have resulted in lighter-skinned phenotypes. Unlike the MC1R where relaxation of selection constraints were observed in non-Africans, the new AIM1 polymorphism has been positively selected.

The time of the common ancestor of alleles bearing the haplotype is estimated to be 10,965 years, although the 95% confidence interval is wide from 1,328 to 39,609 years. We should probably not speculate on what triggered the selection based on this very uncertain dating, but the repopulation of Europe after the last glaciation may be a candidate. As humans spread to higher latitudes, they may have been subjected to higher selective pressures for light pigmentation. It would be interesting to determine the frequency of the polymorphism in different Caucasoid populations and determine the most likely ancestral populations.

Homo sapiens gene MC1R, encoding melanocortin 1 receptor (alpha melanocyte stimulating hormone receptor)

Beyond MC1R

New locus for skin color?