title: The timing of pigmentation lightening in Europeans.
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.
authors.affiliation: IPATIMUP, Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Porto, Portugal. sbeleza@ipatimup.pt
authors.forename: Sandra
authors.initials: S
authors.lastname: Beleza
authors.forename: António M
authors.initials: AM
authors.lastname: Santos
authors.forename: Brian
authors.initials: B
authors.lastname: McEvoy
authors.forename: Isabel
authors.initials: I
authors.lastname: Alves
authors.forename: Cláudia
authors.initials: C
authors.lastname: Martinho
authors.forename: Emily
authors.initials: E
authors.lastname: Cameron
authors.forename: Mark D
authors.initials: MD
authors.lastname: Shriver
authors.forename: Esteban J
authors.initials: EJ
authors.lastname: Parra
authors.forename: Jorge
authors.initials: J
authors.lastname: Rocha
mesh_terms: D000349:Africa; D000483:Alleles; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism; D017920:Antiporters / Q000235:genetics / Q000378:metabolism; D044466:Asian People / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005006:Ethnicity / Q000235:genetics; D005060:Europe; D019143:Evolution, Molecular; D056426:Genetic Loci; D006239:Haplotypes; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018895:Microsatellite Repeats; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D012641:Selection, Genetic; D012880:Skin Pigmentation / Q000235:genetics*; D044465:White People / Q000235:genetics*
chemical_list: D000951:Antigens, Neoplasm; D017920:Antiporters; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; C506584:SLC24A5 protein, human; C510061:SLC45A2 protein, human; D004247:DNA; D010088:Oxidoreductases; C489799:TYRP1 protein, human