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The Evolution Of The Human Body Video

Why do people from different parts of the world have different colored skin?

As early humans moved into hot, open environments in search of food and water, one big challenge was keeping cool. The adaptation that was favored involved an increase in the number of sweat glands on the skin while at the same time reducing the amount of body hair. With less hair, perspiration could evaporate more easily and cool the body more efficiently.

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But this less-hairy skin was a problem because it was exposed to a very strong sun, especially in lands near link equator.

Melanin, the skin's brown pigment, is a natural sunscreen that protects tropical peoples from the many harmful effects of ultraviolet UV rays. UV rays can, for example, strip away folic acid, a nutrient essential to the development of healthy fetuses. Yet when a certain amount of UV rays penetrates the skin, it helps the human body use vitamin D to absorb the calcium necessary for strong bones. This delicate balancing act explains why the peoples that migrated to colder geographic zones with less sunlight developed lighter skin color. As people moved to areas farther from the equator with lower UV levels, natural selection favored lighter skin which allowed UV rays to penetrate and produce essential vitamin D.

The darker skin of peoples who lived closer to the equator was important in preventing folate deficiency. Measures Thr skin reflectance, a way to quantify skin color by measuring the amount of light it reflects, in people around the world support this idea. While UV rays can cause skin cancer, because skin cancer usually affects people after they have had children, it likely had little effect on the evolution of skin more info because evolution favors changes that improve reproductive success. Th is also a third factor which affects skin color: coastal peoples who eat diets rich in seafood enjoy this alternate source of vitamin D.

That Bodg that some Arctic peoples, such as native peoples of The Evolution Of The Human Body and Canada, can afford to remain dark-skinned even in low UV areas.

In the summer they get high levels of UV rays reflected from the surface of snow and ice, and their dark skin protects them from this reflected light. Skip to main content.

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