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

Because mates have selected for it. There is no advantage incurred by someone in the far north with extra melanin, so they aren’t more likely to be represented at mating age. So at that point it just becomes a mates preference.

Remember that not every trait is passed because it imparts a survival advantage. A lot of them are imparted because it provides a purely mating advantage.