1. They have.
2. Sub-Saharan Africa doesn't have the required plants & animals that are needed to jump from a hunter gather society to an agricultural one.
If you stuck stone age White people in Africa they would likely be in a similar state. 
Hey speaking of you being a reprehensible coward do you remember when you repeatedly told someone to kill themselves?
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"Look at this beautiful woman" Lol, what's your point again? I don't think this is helping it.

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Sorry, I'm going to go with the work of an expert in the field over some rando schmuck on Twitter.