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

The human body is very good at conserving energy. If something is not needed, it will be produced in smaller quantities.

This is why building muscle is not a one-and-done thing, but requires constant training to maintain. Unused muscle is broken back down again.

Humans in colder climates DO produce more melanin when exposed to bright sunlight, this is what a tan is, but when the melanin is no longer needed it is no longer produced and lost along with regular shedding of dead skin cells.