Are they really though?
There aren't really "the black people" and " the white people". You can point to statistics, but statistics don't tell you anything about individuals. Individuals are what you should be focusing on. Yeah, individuals tend to be distinctly different.
I assure you there's a 100 million "white people" who are very different "mentally" to myself. But that does not mean I'm "asian" or "black" because I'm not an "average person" for this demographic.
I mean, some of the descendants of slaves have better muscle fiber, but that's because of 100's of years of selective breeding done in Africa and Middle East and continued in USA and other countries where the slaves were sold to.