Human skin color is primarily due to the presence of melanin in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath. Variation in natural skin color is mainly due to genetics, although the evolutionary causes are not completely certain. According to scientific studies, natural human skin color diversity within populations is highest in Sub-Saharan African populations, with skin reflectance values ranging from 19 to 46 (med. 31) compared with European and East Asian populations which have skin reflectance values of 62 to 69 and 50 to 59 respectively. The term "range" is loosely defined in this case, as African albinos have obviously not been taken into consideration when calculating the "range".
The natural skin color can be darkened as a result of tanning due to exposure to sunlight. The leading theory is that skin color adapts to intense sunlight irradiation to provide partial protection against the ultraviolet fraction which produces damage and thus mutations in the DNA of the skin cells. Other factors that can modify skin color include protection from ambient temperature, infections, skin cancer or frostbite, an alteration in food, and sexual selection.
The social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status and racism.
Read more about Human Skin Color: Melanin and Genes, Evolution of Skin Color, Irregular Pigmentation, Exposure To Sun, Geographic Variation, Social Status and Racism
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“The great fact was the land itself, which seemed to overwhelm the little beginnings of human society that struggled in its sombre wastes. It was from facing this vast hardness that the boy’s mouth had become so bitter; because he felt that men were too weak to make any mark here, that the land wanted to be let alone, to preserve its own fierce strength, its peculiar, savage kind of beauty, its uninterrupted mournfulness.”
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—Eleanor Roosevelt (1884–1962)
“Good Hamlet, cast thy nighted color off.”
—William Shakespeare (1564–1616)