The Genetics and Evolution of Human Pigmentation.

Human skin pigmentation is one of the most visible and variable traits among populations and has been shaped primarily by natural selection in response to ultraviolet (UV) radiation. This review synthesizes the current understanding of the genetic and evolutionary mechanisms that underlie pigmentation differences across the globe. The roles of key pigmentation-related genes, such as MC1R, SLC24A5, TYR, and OCA2, are examined in terms of how different versions of these genes have been favored in different UV environments to balance the need for photoprotection and vitamin-D synthesis. Evidence of convergent evolution in lighter skin pigmentation is explored among populations in Europe and East Asia, along with the relatively stable presence of darker pigmentation alleles in equatorial regions. We also highlight how recent research has integrated ecological, anthropological, and genomic data to paint a fuller picture of these adaptive patterns. Finally, we discuss the biomedical implications of these evolutionary processes, including how historical adaptations influence current differences in skin cancer risk, vitamin-D metabolism, and pigmentary disorders. By tracing the evolutionary history of skin color, this review emphasizes the intricate interplay between our genetics, environment, and health.