Eli5 Is Melanin production based on Genetics or on Geographical area?
In: Biology
Yes.
What the basic color of your skin is – its ordinary melanin conent – is based on the genes you got from mom and dad, and also on how those genes are being expressed in various places. (This is why Black people have pink tongues and palms of their hands, for example. Their body instructions said to put less melanin there than on their skin in other places.)
Geographical area has some influence on what kind of people live there, and how they adapt over generations to local conditions. In this case, how much ultraviolet exposure there is, how much sunlight there is on average, and how far toward one of the Poles you are, as well as the amount of shade trees or mountains-and-valleys around, all influence things like how long days are and how much sun you’re exposed to at what angle during the day.
This in turn helps select people whose skin colors are tuned towards that sun amount, slowly slowly over generations. And you end up with pale pink people living in the extreme North and South, tan or olive people living in the median latitudes, and darker brown people living near the Equator, with the ones living where there’s more sun exposure evolving to have more melanin in their skin to block it out.
(Plus which, it turns out that having paler skin further north or south helps you get enough vitamin D, made by sunlight on your skin stimulating a chemical process, so that’s another factor driving this; otherwise, we all might still be pretty brown because we’d have nothing pushing us to be paler.)
Then, of course, modern transportation technology steps in, and people go visiting and move all over the world, and marry the people they meet there and have kids, and now it’s not too difficult to find someone near you who has a wildly different amount of melanin in their skin…
–Dave, and NONE of this indicates “race”. at all. They’re all humans, from the human race. They all can interbreed and have fertile children.
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