Are you saying that white people are inherently less physically able than black people? How do you measure physical ability? There are physical sports where white people are overrepresented (like hockey), so let's not pretend that top white athletes are not competitive. It's entirely possible that there is systemic racism in basketball. Are childhood training dollars spent disproportionately in black communities? For instance I remember Clinton's midnight basketball program.. how many white kids showed up to that?
Statistically speaking there are more very tall black African Americans than white Americans. I'm not sure that statistically African Americans are dumber though, if you were to somehow measure raw intelligence and potential rather than academic results.