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

Human skin produces vitamin D in response to sunlight. We need that. But Melanin also obstructs that sunlight, which is a natural defense against UV light.. sun burns, skin cancer, etc.

It’s not the colder temperature so much as it is the reduced sun exposure. To get more vitamin D, evolution took away some of the Melanin. We traded off some of the UV protection to get better vitamin D production.

So, if you’re not getting much sun exposure, consider taking a vitamin D supplement. (talk to your doctor, blah blah blah, not medical advice)