All humans are 99.9% genetically identical and we are 97% genetically identical to chimpanzees. There are some genes within the 0.1% of differences that are very obvious such as eye color and skin color. In the 1800’s, many scientists believed that skin color indicated different races of humans. This mistake led to many tragic outcomes as the result of racism and eugenics.
The actual source of variations in skin color has to do with two things: 1) protection from the ultraviolet rays of the sun which can damage the skin cells genes and lead to skin cancer; and 2) the production of vitamin D in the skin from a fat (7-dehydrocholesterol) requiring the action of ultraviolet radiation from the sun.
Humans evolved first in Africa where there was a lot sunlight so that vitamin D production was not a concern but protection from ultraviolet light and sunburn was a concern. The natural sunblock in the skin comes from a substance called melanin made from one of the amino acids in protein called tyrosine. Melanin darkens the skin as it accumulates so that the more melanin there is , the darker the skin gets.
When humans migrated to Europe from Africa, the sunlight was much less especially in the winters. Now the main concern was production of vitamin D rather than sunlight protection. So the amount of melanin in the skin was reduced by turning down the genes producing melanin. In fact, in some Scandinavians, there is a pigment that actually amplifies the radiation from the sun.
When people from England settled in Australia, they brought their Northern European skin with them. As they were not adapted to the strong sunlight in Australia, there is now an epidemic of skin cancer there as there is in the Southwest United States where many “snowbirds” from the Great Lakes states retire with their Scandinavian-derived skin. For these individuals consuming adequate beta-carotene from orange vegetables like carrot, sweet potato and pumpkin or taking supplements with at least 7 mg of beta-carotene daily is important. Of course, wearing a sunscreen with adequate SPF of at least 30 when exposed to the sun is also vital to prevent skin cancer.
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