The genetic architecture of human skin pigmentation: evolution and adaptation across global populations

Human skin pigmentation is a dynamic and highly adaptive trait influenced by genetic, environmental, and cultural factors. It is driven by variation in ultraviolet radiation, governed by a complex polygenic structure, and further modulated through gene-culture interactions. This review synthesizes advances from evolutionary biology, anthropology, molecular genetics, and gene-culture coevolution to provide an integrated framework for understanding global diversity of pigmentation. We take a distinct approach by focusing on the major evolutionary hypotheses and the polygenic architecture underlying pigmentation. We emphasize both large-effect loci, including SLC24A5, SLC45A2, and MC1R, as well as population-specific adaptive variants identified through recent genomic and functional studies. Using evidence from diverse global populations, we examine how natural selection, demographic processes, and convergent evolution have jointly structured present-day variation in human skin pigmentation. We further emphasize how cultural practices, including clothing, diet, and mobility, have generated gene-culture feedback that modulates selective pressures over evolutionary timescales, underscoring the need for integrative, multi-ethnic research approaches that trace the temporal variation of skin pigmentation and advance its broader biomedical and anthropological implications.