Question: Why do different ethnic races have different skin colours?

Tom Lister answered on 5 Jul 2012:

Excellent question.

Best theory around is probably the Vit D one. First of all, as humans lost their hair (our ancestors were hairy) we had to protect our skin from the sun – so we started producing lots of melanin (the brown stuff that gives our hair and skin its colour) which is brilliant at doing this, it even clusters over the cell nuclei which are the most venurable bits to sun-damage. As we began to migrate further North, those of us with lighter skin managed to cope better because they were able to produce more vitamin D (we get almost all of our vit D from our skin, which needs sunshine to produce it – the dark pigment stops this).

So cultures that moved further North required lighter skin, but those that stayed in sunny climates were better off being dark – we evolve in different directions. This has only been over a relatively short times, so humans are still all remarkably similar (compare us to dogs, for example).

The only exception to this is the eskimos, who remained relatively dark but got their vitamin D from a high fish diet.

That’s natural selection, there is also a bit of sexual selection, as paler people were more desirable in many parts of Northern Europe for a few hundred years (I’m not sure if the impact of this was significant though)