Melanin: Difference between revisions

Melanin is a pigment that affects skin, eye, and hair colour in humans and other mammals. It is produced by melanocytes, which are found in the bottom layer of the skin's epidermis. Some individual animals and humans have no or very little melanin in their bodies, which is a condition known as albinism. Melanin helps protect the skin from damage caused by ultraviolet (UV) radiation from the sun. Most people's skin darkens when exposed to UV light, giving them more protection when it is needed.

People whose ancestors lived for long periods in the regions of the globe near the equator generally have more active melanocytes, and therefore larger quantities of melanin in their skins. This makes their skins dark brown or black and protects them against high levels of UV exposure. In areas of the globe closer to the poles, people have far less need for protection from ultraviolet radiation, so their skin is usually lighter in colour. This allows sunlight to stimulate vitamin D production.

The most recent scientific evidence indicates that all people originated in Africa. As a result, all original people had relatively large numbers of active melanocytes and, accordingly, darker skin. As some of these original tribes of people migrated and settled in areas of Asia and Europe, their melanin production gradually decreased to allow acclimation to climates where radiation from the sun was less intense.

It is estimated that this color evolution in an immigrated populace takes approximately 10,000 years to complete. This phenomenon is probably one of natural selection; those people, whose skin is too dark in color, cannot produce sufficient amounts of Vitamin D to sustain good health.

As with peoples that migrated northward, those with light skin that migrated southward had to acclimate to the much stronger solar radiation. Those people, who produced more skin-protecting melanin, were less likely to suffer from skin cancer, as well as other health problems related to exposure to strong solar radiation, including the photodegradation of certain vitamins such as riboflavins, carotinoids, tocopherol, and folate.

Freckles and moles are formed where there is a greater concentration of melanin in the skin.

Albinism is a condition in which an animal (such as a human or a mouse) is incapable of producing melanin, and hence appears white with pink eyes.

To be covered:

• eumelanin
• phaeomelanin

The concentration of melanin in an individual's tissues has long been of social importance, as many people and societies are racist, and regard so-called "racial" characterstics including amount of skin and hair pigmentation as being determinative of a person's intelligence, character, and general merits. Many human societies are divided between socially-, culturally-, and economically-distinct groups possessing darker or lighter pigmentation. Examples of such divisions being institutionalized are apartheid in South Africa, and segregation in the United States. Many other societies remain informally divided based on melanin concentration. See also white supremacy, Nazism, colonialism

• Black supremacy
• carotene
• human skin color
• melanism
• red hair