Pray tell, as far as I know pretty much everything relating to intelligence is discussed and far from settled-
Also, I once saw a documentation of a woman with Downs syndrome.
The thing is, she was a genius, at least for people with Downs, she was basically a functioning normal adult with average intelligence, she just had the look of someone with one chromosome too many.
That however would not lead me to conclude that those people on average have the same potential with a normal genome and yes, for genetic reasons.
Be that as it may, the fact of the matter is that those people in Africa have a low IQ now, no matter what their potential may or may not be.
Maybe it is just a vicious circle, but a vicious circle involving a few hundred million people is not going away just because we mean well.