> I have a Hacker News Health Theory (TM) about melanin content: why would human skin color vary so reliably based on distance from equator if sun wasn't really

> I have a Hacker News Health Theory (TM) about melanin content: why would human skin color vary so reliably based on distance from equator if sun wasn't really, really important? Can you expand on that? All I get from it is that protecting yourself from UV is really important, but producing extra melanin is somewhat costly, so evolution selects for just as much melanin as your environment requires, no more.