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?

Question

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

Answer 1

Lighter skinned people make more vitamin D when hit by sunlight, darker skin people make less.

People who evolved in places with low levels of sunlight evolved lighter skin to absorb more D over the long winters. Farther north from the equator you go, lighter the skin of the natives, with a few exceptions.