Numbers may have started in Egypt, a mixed, not sub-saharan culture.
Writing probably started in Sumeria/Mesopotamia.
Sub-saharan Africa would still live like they had for Hundreds of Thousands of years (and some still do) were it not for the importation of other dispersed Cultures/races.
AIDS/Ebola (Malaria, Polio, Famine, etc), and the like would have certainly and continuously wiped out Large parts, if not Most of the continent were it not for Western Medicine. And of course, Tribal warfare. Nature was 'in balance' and primitive before IQ wiped out other species.
While slavery was intolerably cruel, these people at least had/Now Have existence and Much better lives due to their importation. Though probably 1/3 or more died in hideous transit.
There is No large movement to return to Africa.
Liberia, Center of the recent Ebola outbreak, was a small effort to do just that. How they doing?
Subsharan Africa is pretty much a disaster as far as self-government ("Tribes with flags"), except for those countries that Did have Colonial vestiges: Western Peoples/systems. ie South Africa.