It's not really a secret that when you mix species together in nature they don't do well. Hell, even the same species of ants from different colonies will kill each other if you mix them together. Ravens and crows don't flock together. When you put a bunch of black people together, you get Africa. When you put a bunch of white people together, you get Western Civilization. So it's no surprise that the blacks' areas look more like Africa than they do America. "Race" really is a social construct, they are actually phenotypical sub-species. Phenotypical sub-species are extremely different all throughout nature. For example: they only use certain dog breeds for police and military work for a reason. You don't need to look any farther than what you can see in your back yard for the answer.