I also disagree that 'selective slave breeding' is a real factor in the seemingly disproportionate number of athletic african americans. I think it is much more likely that when Europeans sailed to Africa to get slaves, they probably didn't just grab the first ones they saw. Most likely they purposely selected the biggest, strongest men they could find. If I were going to buy a horse to pull a wagon all day, you bet your ass I would buy the biggest one I could find. (no, I am not comparing African Americans to draft animals, I am the work a slave had to do to the work a horse would have to do.)
In addition to that, most people dont consider that most African people live in a very harsh enviroment, hindering cultural development. Europe and Asia have been "civilized" (for lack of a better word) for a far greater time, thats why all the great empires of the world have been European or Asian. (China, Japan, Mongolia, Russia, Spain, France, England, Italy, Germany, ect.) African people have had to live a much more physical life over the past thousand years, keeping their bodies stronger. This is evident if you look at other primate species, we are by far the weakest, why? Because we were removed from a physical, natural selective enviroment, this is probably why we are virtually hairless with fragile fingernails, and terrible reaction times.
Thinking that a few hundred years of selectively breeding slaves is a bigger factor than enviroment for millions of years, or slave owners literally picking the biggest slaves is just silly.