For hundreds of years, human skin color has been used as a marker of race. Now, science is uncovering the intricate relationship between skin color and environment. When our ancient ancestors in Equatorial Africa lost their body hair and ventured out into the open Savannah, their skin had to become dark to resist strong UV radiation. Perfectly adapted to the environment, the black skin of Africans is one of Nature's greatest achievements for the survival of the human species.