Book Excerpt from Living Color

Research on the evolution of human skin pigmentation began before information on the DNA sequences of human pigmentation genes was available. Anthropologists deduced that hominids living outside the tropics would have been under evolutionary pressure to lose some of the pigment in their skin as they moved north. This deduction was based on the fact that dark skin and reduced UVB exposure would have made it difficult for people to produce enough vitamin D in their skin to stay healthy and reproduce. Therefore, skin would have had to become lighter. This is the basis for what has long been known as the "vitamin D hypothesis" of human skin pigmentation. Some authorities argued that the body’s ability to store vitamin D could get humans through the months of the year when active production in the skin was not possible. But the time limit for vitamin D storage is about two months, ...