[August]

I think you guys overestimate the harmonious nature of primitive life. Survival was anything but guarenteed. You limit human "range" to such a small area and you vastly increase the risk that war, overpopulation, famine, disease, climate change or any number of other disasters could wipe out the entire species in the space of a generation.

Besides, just because European and Asian explorers found Africa fairly primitive it doesn't prove that had Africans been left unmolested they wouldn't have had their own industrial revolution at some point. One might make an argument that harsh environments retard advancement but I see no evidence that it would stop altogether.