The vast array of human skin colors has long been the subject of cultural fascination and anthropological inquiry, but this focus ignores the complexity of skin as the interface between humans and the environment. Evidence from our primate relatives suggests unique adaptations in sensory receptors in the skin vary with locomotor, foraging, and reproductive behaviors particular to certain species. Such enhanced tactile perception and the neural circuitry essential for its interpretation likely contributed to the evolution of larger brain size and tool use in our hominid ancestors. The shift to bipedalism and expanded ecological niche that define hominids was also made possible by skin. Loss of fur and concomitant evolution of increased sweating allowed the maintenance of thermal homeostasis, and epidermal keratin strengthened the immunological and physical properties of exposed skin. Intense evolutionary pressure contributed to rapid pigmentation of this newly naked, highly innervated skin. Thus, pigmentation defines much of the modern variation in human skin, with complex medical implications. Frequently cited as an indicator of melanoma risk, medical understanding of melanin has moved beyond simple photoprotection, with research suggesting links between human pigmentation variation and heart disease, nicotine addiction, psychiatric illness, and neurological disorders. In these ways, the evolutionary history of human skin has important implications for what health means today.