eli5: If more melanin is advantageous in warm climates, why is less of it advantageous in colder climates? Wouldn’t darker skin still be most advantageous in cold climates where it might occasionally be hot?
In: 1641
No.
It’s an adaptive advantage, and the lack of it is also an adaptive advantage. Skin with less melanin is more efficient at gleaning vitamin D from smaller amounts of sunlight, but is also more easily burned by prolonged exposure. This is why people who live closer to the poles tend to have less melanin. People with more melanin are more suited to sunnier climates and longer exposure to the sun, because their skin takes vitamin D in more gradually, and is less prone to burning.
Beyond that, and this is just anecdotal, but people with more melanin also seem to be more sensitive and uncomfortable with the cold. And people with less melanin seem to be more easily exhausted by heat.
Of course we’re all conscious beings and can take measures to adapt to wherever we find ourselves in, so it’s not that big of a deal in most cases, however people with darker skin ARE more prone to vitamin D deficiency in northern climates, which is actually a pretty big health issue. Not one that can’t be dealt with, but one that a lot of people just seem to be unaware of.
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