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The Timing of Pigmentation Lightening in Europeans

  1. Jorge Rocha*,1,2,3
  1. 1IPATIMUP, Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Porto, Portugal
  2. 2CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos da Universidade do Porto, Vairão, Portugal
  3. 3Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal
  4. 4Department of Statistical Genetics, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
  5. 5Department of Anthropology, University of Toronto at Mississauga, Ontario, Canada
  6. 6Department of Anthropology, Pennsylvania State University
  1. ↵*Corresponding author:
    E-mail: jrocha{at}cibio.up.pt; sbeleza{at}ipatimup.pt.

Abstract

The inverse correlation between skin pigmentation and latitude observed in human populations is thought to have been shaped by selective pressures favoring lighter skin to facilitate vitamin D synthesis in regions far from the equator. Several candidate genes for skin pigmentation have been shown to exhibit patterns of polymorphism that overlap the geospatial variation in skin color. However, little work has focused on estimating the time frame over which skin pigmentation has changed and on the intensity of selection acting on different pigmentation genes. To provide a temporal framework for the evolution of lighter pigmentation, we used forward Monte Carlo simulations coupled with a rejection sampling algorithm to estimate the time of onset of selective sweeps and selection coefficients at four genes associated with this trait in Europeans: KITLG, TYRP1, SLC24A5, and SLC45A2. Using compound haplotype systems consisting of rapidly evolving microsatellites linked to one single-nucleotide polymorphism in each gene, we estimate that the onset of the sweep shared by Europeans and East Asians at KITLG occurred approximately 30,000 years ago, after the out-of-Africa migration, whereas the selective sweeps for the European-specific alleles at TYRP1, SLC24A5, and SLC45A2 started much later, within the last 11,000–19,000 years, well after the first migrations of modern humans into Europe. We suggest that these patterns were influenced by recent increases in size of human populations, which favored the accumulation of advantageous variants at different loci.

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  1. Mol Biol Evol 30 (1): 24-35. doi: 10.1093/molbev/mss207 First published online: August 25, 2012
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