Re: "why Blacks are such fast runners?"
Or it could be that it was more useful to be a fast runner for humans in Africa than it was for the humans who migrated north. While we all came from Africa if you go back a hundred thousand years or so, to the extent that fast running was more important for survival and having more children (i.e. higher social status) in Africa versus Europe/Asia/Americas the ones who left Africa would stop selecting for it as much. We selected for other traits, like lighter skin to allow getting sufficient vitamin D from the sun, digesting milk when we started keeping cattle, and so forth.
At any rate, the difference in speed is pretty small on average as well in the elite category. But when the difference between winning and losing is measured in hundredths of a second, it doesn't take much difference for blacks to be overrepresented in the ranks of elite sprinters.
Which is similar to the difference between men and women that Damore was pointing out. Yes, there's a difference, but it isn't large enough to account for the wide disparity in men and women working in tech. Especially since there is nearly a 50/50 mix in other countries like India and China. The difference in the US is obviously not genetic, unless someone wants to make a case that the difference between men and women in suitability for tech jobs exists only in Caucasians.