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 is there because of sun intensity, not temperature.

Essentially it reduces skin damage from UV.
However, some UV is essential for vitamin D production, so in areas with less UV from the sun, it can be detrimental to your health.

Naturally uv is more intense in the tropics and around equator and is why peoples such as subsaharan africans, dravidic indians and papuans are dark skinned whereas northern europeans and uralic peoples are by and large very light skinned, as UV is much lower.

Interestingly, Inuit peoples are *relatively* quite dark skinned, as the suns light largely reflects off snow, almost giving you a second “dose” of UV, so need more melanin to protect their skin.