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Melanin and genes

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Melanin is produced by cells called melanocytes in a process called melanogenesis. Melanin is made within small membrane–bound packages called melanosomes. As they become full of melanin, they move into the slender arms of melanocytes, from where they are transferred to the keratinocytes. Under normal conditions, melanosomes cover the upper part of the keratinocytes and protect them from genetic damage. One melanocyte supplies melanin to thirty-six keratinocytes according to signals from the keratinocytes. They also regulate melanin production and replication of melanocytes. People have different skin colors mainly because their melanocytes produce different amount and kinds of melanin. The genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades. Differences in skin color are also attributed to differences in size and distribution of melanosomes in the skin. Melanocytes produce two types of melan...
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Age

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In hominids, the parts of the body not covered with hair, like the face and the back of the hands, start out pale in infants and turn darker as the skin is exposed to more sun. All human babies are born pale, regardless of what their adult color will be. In humans, melanin production does not peak until after puberty. The skin of children becomes darker as they go through puberty and experience the effects of sex hormones. citation needed This darkening is especially noticeable in the skin of the nipples, the areola of the nipples, the labia majora in females, and the scrotum in males. In some people, the armpits become slightly darker during puberty. The interaction of genetic, hormonal, and environmental factors on skin coloration with age is still not adequately understood, but it is known that men are at their darkest baseline skin color around the age of 30, without considering the effects of tanning. Around the same age, women experience darkening of some areas of their skin. Hu...
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Evolution of skin color

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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. The emergence of skin pigmentation dates to about 1.2 million years ago, under conditions of 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. 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 ...
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