Why has extreme genetic diversity persisted in Sub-Saharan Africa despite geographic contiguity of different ethnic groups?

by hyphenomicon

Most explanations for Africa's genetic diversity attribute it simply to the accumulation of time in which diversity can accrue. That sort of makes sense, but it's not clear to me why the accumulating diversity would so stubbornly persist.

KippyPowers

I think this question would be better suited for r/AskAnthropology. We have some biological anthropologists there who can discuss this topic with you.