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Edited by Nina G. Jablonski, The Pennsylvania State University, University Park, Pennsylvania, and accepted by the Editorial Board February 1, 2014 (received for review September 4, 2013)
Significance
Eye, hair, and skin pigmentation are highly variable in humans, particularly in western Eurasian populations. This diversity may be explained by population history, the relaxation of selection pressures, or positive selection. To investigate whether positive natural selection is responsible for depigmentation within Europe, we estimated the strength of selection acting on three genes known to have significant effects on human pigmentation. In a direct approach, these estimates were made using ancient DNA from prehistoric Europeans and computer simulations. This allowed us to determine selection coefficients for a precisely bounded period in the deep past. Our results indicate that strong selection has been operating on pigmentation-related genes within western Eurasia for the past 5,000 y.
Abstract
Pigmentation is a polygenic trait encompassing some of the most visible phenotypic variation observed in humans. Here we present direct estimates of selection acting on functional alleles in three key genes known to be involved in human pigmentation pathways—HERC2, SLC45A2, and TYR—using allele frequency estimates from Eneolithic, Bronze Age, and modern Eastern European samples and forward simulations. Neutrality was overwhelmingly rejected for all alleles studied, with point estimates of selection ranging from around 2–10% per generation. Our results provide direct evidence that strong selection favoring lighter skin, hair, and eye pigmentation has been operating in European populations over the last 5,000 y.
Footnotes
↵1Present address: Department of Ecology and Genetics, Evolutionary Biology, Uppsala University, 75236 Uppsala, Sweden.
- ↵2To whom correspondence should be addressed. E-mail: m.thomas{at}ucl.ac.uk.
Author contributions: S.W., M.G.T., and J.B. designed research; S.W., A.T., M.U., N.H., and M.G.T. performed research; A.T. and M.G.T. contributed new reagents/analytic tools; E.K. and W.S. coordinated the acquisition of the archaeological sample material and provided background information; I.D.P. provided archaeological sample material and background information; M.G.T. and J.B. coordinated this study; S.W., A.T., N.H., and M.G.T. analyzed data; and S.W., A.T., K.K., E.K., M.K., M.U., N.H., I.D.P., W.S., M.G.T., and J.B. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. N.G.J. is a guest editor invited by the Editorial Board.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1316513111/-/DCSupplemental.
Freely available online through the PNAS open access option.
Direct evidence for selection on pigmentation
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