I'll make two serious points about this. People claim to be so certain about things that were 10,000 years ago or whatever. I really doubt they even know that well based on some scant evidence that was found. The idea of having sub-Saharan retards spreading anywhere is ridiculous. If they can't go steal a neighboring tribe's stuff, then they're not going anywhere, especially not somewhere completely uninhabited and inhospitable. I suppose it's possible people had darker skin, but they weren't nig nogs. That's for sure. The more southern and eastern you get, the Caucasoid type people have somewhat darker skin. There are environmental adaptations in people such as Inuits for cold and Tibetans for high altitude, but I don't know the mechanism by which these things come about. I doubt that there is enough pressure for natural selection alone to accomplish this. It seems organisms are picking up environmental info and skewing things to be adapted to the environment. I would guess that sperm production in men could be a possible route this takes place.