Abstract
Human pigmentation is a highly diverse trait among populations, and has drawn particular attention from both academic and non-academic investigators for thousands of years. To explain the diversity of human pigmentation, researchers have proposed that human pigmentation is adapted for ultraviolet radiation and driven by natural selection. Although studies have detected signals of natural selection in several human pigmentation genes, none have quantitatively investigated the historical selective pressures on pigmentation genes during different epochs and thoroughly compared the differences in selective pressures between different populations. In the present study, we developed a new approach to dissect historical changes of selective pressures in a multiple population model by summarizing selective pressures on multiple genes. We collected genotype data of 16 critical human pigmentation genes from 15 public datasets, and obtained data for 3399 individuals of five representative populations from worldwide. Our new approach quantified not only a recent incremental change of selective pressure (0.0068/generation) in modern Europeans, but also a significant historical increase of selective pressure (0.178/generation) on light pigmentation shared by all Eurasians during the out-of-Africa event. We excluded the relaxation of selective pressures, and favored diversifying selection as the single explanation for the cause of light pigmentation in Eurasians, a long-standing puzzle in the evolution of human pigmentation. Our results suggest that epistasis plays important roles in the evolution of human pigmentation, partially explaining diversifying selection on human pigmentation among populations.
- Posted January 25, 2018.
