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

Melanin protects against UV damage, but as a result it also decreases the amount of UV available for vitamin D production. Near the equator, that’s fine because there’s more than enough sun. Near the poles, having a lot of melanin increases risk of vitamin D deficiency.