The OTF "why aren't we all black?" thread, then

[Rogin the Armchair fan]

I'm sure we've done this before.

But I don't remember. We're all descended from people who were living in Africa, who would have looked like the people who still, er, live in Africa.

So where did us "white" people come from? Is it anything to do with "evolution"? The different models of humans, from Indonesians to Caucasians to Mongolians? How did that actually "happen", in such a short space of evolutionary time (30,000 years, or 2,000 generations)?

[Guest]

The OTF "why aren't we all black?" thread, then

Current thinking is that once our descendants had migrated to colder climates, the melanin in their skin was a disadvantage because it blocked some of the sunlight required to manufacture Vitamin D.
Those with lighter skin had a slight evolutionary advantage, so could reproduce more successfully and eventually this led to other races.

[Ginger Yellow]

The OTF "why aren't we all black?" thread, then

How did that actually "happen", in such a short space of evolutionary time (30,000 years, or 2,000 generations)?

Skin pigmentation is a pretty trivial thing to change at at a population level over not that many generations in any species. There are plenty of other comparable evolutionary variations in humans like adult lactose tolerance in historically cow-herding populations, sickle cell anemia/malaria resistance in Sub-Saharan populations etc.