Well, actually...
Low IQ is common in tribal communities that intermarry. Africa, Middle East, Latin American Tribes...
It's even continuing here, in the US, where ghetto denizens are breeding without knowing (or caring) that they are first cousins, half-siblings, or even father and daughter.
Low-IQ societies don't produce forward-thinking leaders.
I have worked with Physicians ans Anesthesia students from Africa, pretty sharp folks.