<P> Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance . One copy of each of the various genes is inherited from each parent . Each gene can come in several alleles, resulting in the great variety of human skin tones . Melanin controls the amount of ultraviolet (UV) radiation from the sun that penetrates the skin by absorption . While UV radiation can assist in the production of vitamin D, excessive exposure to UV can damage health . </P> <P> Loss of body hair in Hominini species is assumed to be related to the emergence of bipedalism some 5 to 7 million years ago . Bipedal hominin body hair may have disappeared gradually to allow better heat dissipation through sweating . </P> <P> The emergence of skin pigmentation dates to after this, perhaps some 1.5 million years ago (about the time of the emergence of Homo heidelbergensis), when the earth endured a megadrought that drove early humans into arid, open landscapes . Such conditions likely caused excess UV - B radiation . This favored the emergence of skin pigmentation in order to protect from folate depletion due to the increased exposure to sunlight . A theory that the pigmentation helped counter xeric stress by increasing the epidermal permeability barrier has been disproved . </P> <P> With the evolution of hairless skin, abundant sweat glands, and skin rich in melanin, early humans could walk, run, and forage for food for long periods of time under the hot sun without brain damage due to overheating, giving them an evolutionary advantage over other species . By 1.2 million years ago, around the time of Homo ergaster, archaic humans (including the ancestors of Homo sapiens) had exactly the same receptor protein as modern sub-Saharan Africans . </P>

Most responsible for the skin color of dark