Actually, reading this thread made me remember a question that someone came up with, possibly here, quite some time ago. The question was:

"Why did so much evolution occur in East Africa? Or did it?"

Which is two questions, I know, but you can see where this was going. The assumption seems to be that since so many fossils of so many different types of hominids have been found there, that that is where the evolution must have occurred. But is that a good assumption?

The question is rhetorical, obviously, since we only have evidence of these hominids from this one area. But it makes me wonder ...