Rapid evolution of a skin-lightening allele in southern African KhoeSan. Lin, M., Siford, R. L., Martin, A. R., Nakagome, S., Möller, M., Hoal, E. G., Bustamante, C. D., Gignoux, C. R., & Henn, B. M. Proceedings of the National Academy of Sciences of the United States of America, 115(52):13324–13329, December, 2018.
doi  abstract   bibtex   
Skin pigmentation is under strong directional selection in northern European and Asian populations. The indigenous KhoeSan populations of far southern Africa have lighter skin than other sub-Saharan African populations, potentially reflecting local adaptation to a region of Africa with reduced UV radiation. Here, we demonstrate that a canonical Eurasian skin pigmentation gene, SLC24A5, was introduced to southern Africa via recent migration and experienced strong adaptive evolution in the KhoeSan. To reconstruct the evolution of skin pigmentation, we collected phenotypes from over 400 ≠Khomani San and Nama individuals and high-throughput sequenced candidate pigmentation genes. The derived causal allele in SLC24A5, p.Ala111Thr, significantly lightens basal skin pigmentation in the KhoeSan and explains 8 to 15% of phenotypic variance in these populations. The frequency of this allele (33 to 53%) is far greater than expected from colonial period European gene flow; however, the most common derived haplotype is identical among European, eastern African, and KhoeSan individuals. Using four-population demographic simulations with selection, we show that the allele was introduced into the KhoeSan only 2,000 y ago via a back-to-Africa migration and then experienced a selective sweep (s = 0.04 to 0.05 in ≠Khomani and Nama). The SLC24A5 locus is both a rare example of intense, ongoing adaptation in very recent human history, as well as an adaptive gene flow at a pigmentation locus in humans.
@article{lin_rapid_2018,
	title = {Rapid evolution of a skin-lightening allele in southern {African} {KhoeSan}},
	volume = {115},
	issn = {1091-6490},
	doi = {10.1073/pnas.1801948115},
	abstract = {Skin pigmentation is under strong directional selection in northern European and Asian populations. The indigenous KhoeSan populations of far southern Africa have lighter skin than other sub-Saharan African populations, potentially reflecting local adaptation to a region of Africa with reduced UV radiation. Here, we demonstrate that a canonical Eurasian skin pigmentation gene, SLC24A5, was introduced to southern Africa via recent migration and experienced strong adaptive evolution in the KhoeSan. To reconstruct the evolution of skin pigmentation, we collected phenotypes from over 400 ≠Khomani San and Nama individuals and high-throughput sequenced candidate pigmentation genes. The derived causal allele in SLC24A5, p.Ala111Thr, significantly lightens basal skin pigmentation in the KhoeSan and explains 8 to 15\% of phenotypic variance in these populations. The frequency of this allele (33 to 53\%) is far greater than expected from colonial period European gene flow; however, the most common derived haplotype is identical among European, eastern African, and KhoeSan individuals. Using four-population demographic simulations with selection, we show that the allele was introduced into the KhoeSan only 2,000 y ago via a back-to-Africa migration and then experienced a selective sweep (s = 0.04 to 0.05 in ≠Khomani and Nama). The SLC24A5 locus is both a rare example of intense, ongoing adaptation in very recent human history, as well as an adaptive gene flow at a pigmentation locus in humans.},
	language = {eng},
	number = {52},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	author = {Lin, Meng and Siford, Rebecca L. and Martin, Alicia R. and Nakagome, Shigeki and Möller, Marlo and Hoal, Eileen G. and Bustamante, Carlos D. and Gignoux, Christopher R. and Henn, Brenna M.},
	month = dec,
	year = {2018},
	pmid = {30530665},
	pmcid = {PMC6310813},
	keywords = {Africa, KhoeSan, SLC24A5, adaptation, pigmentation},
	pages = {13324--13329},
}

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