Eli5 Is Melanin production based on Genetics or on Geographical area?
In: Biology
It is based on two factors. First is UV exposure. Second is genetics. This is why black people can exist in the UK and white in Africa. It is also why albinos never produce much at all. UV doesn’t have a huge effect on how much you produce
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.
It’s a mix of both. Genetics will determine what your baseline and maximum possible skin melanin content is. Exposure to UV light will adjust the amount within those theoretical limits.
Those in places with hot sunny environments like Africa have a higher minimum and maximum melanin level, as natural selection keeps it high. While those population that’s migrated to a more temperate climate naturally selected for less. This is because in the sunny environment, the natural protection from UV radiation and sunburn that would make survival harder if not outright impossible due to sun poisoning (yes that’s a thing).
Whereas people in more cloudy temperate climates didn’t need darker skin and the lighter skin tone allows them to absorb more sunlight into their body which helps primarily create vitamin D.
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