Large samples of DNA markers from human populations show that about ten percent of diversity is between populations and the rest within. I prefer to mate with someone who looks like me or like some ideal type. Selection maintains this preference because then my children will look like the ideal type and potential mates will want to mate with them, and so on. This kind of selection amplifies differences between groups, even in the face of low level gene flow, accounting for the disparity between labels and internals in our species. Darwin proposed this mechanism of the genesis of differences, and its most articulate recent advocate is Jared Diamond in The Third Chimpanzee .
Success generates more success.
I don't usually bother because my finding will be invalid in a month, and at any rate the differences are small. If twenty years of PC evolution corresponds to two million years of human evolution, then a month of PC evolution corresponds to about fifteen thousand years of human evolution. Today, if I am deciding where to build my high tech factory then evidence suggests I should build it somewhere where there a lot of people with northeast Asian ancestry. Fifteen thousand years ago most northeast Asians probably became extinct as the last major glacial advance froze them out. Environments, like the PC market, are transient.