To my understanding, there is a proven magnitude, but it vanishes into pretty much unavoidable environmental factors. Some people just turn out to be bad parents, or someone gets stuck with a particularly poor teacher, or a friend turns out to be a bad influence, or any number of person-to-person developmental differences, that all add up to more than one's bloodline.
This makes a lot of sense with how ridiculously flexible the human central nervous system is, and there's a lot of other well known factors involved in cultural development. Sub-Saharan Africa is predominantly a short-sighted shithole because the climate makes food storage a nightmare and there's fuck-all to start with.
Seriously, can anyone point to a place that could have reasonably been the Indus of sub-Saharan Africa? Or how, exactly, they'd have made the jump to iron? Place is livable, but really only that, which is a bit ironic given it's the native environment of humanity. Though such does fit with the usual trend of invasive species being more successful in the new environment...
They
did "make the jump" to iron.
The Zulus had iron blades on their spears, as did most of the other Bantu tribes.
They didn't have any system of writing though, and they never figured out how to use cattle to pull plows or anything like that.
Humanity evolved in east Africa around the Great Rift Valley, which has its southern end on the northern border of South Africa.
Sub-Saharan Africa as we see it today is fucked mostly because it's horrible for food storage, has man killing animals in relative abundance, and has been run roughshod on by countless powers going back to antiquity, so it rarely could create power blocks comparable to the MidEast or Indus Valley. Lack of writing didn't help either.
This however does nothing to support the racists bullshit, because East Africa was fairly civilized for a long, long time, even before the Pharaohs and Axum came around. And West Africa has been interacting with Mediterranean trade and powers since people first set sail.
Modern Sub-Saharan Africa is a shithole mostly because of how colonial powers exploited tribe vs tribe factionalism to create thier colonies, and only put in infrastructure to specific exploitable resources, not for general use by the population. And when the colonial empires collapsed/retreated, all the old grudges and bad blood that colonial powers kept a lid on, while also exploiting it make control easier, came back in full force.
That's before you add in the new resource issues with rare earth's, diamonds, and petro deposits in Africa causing renewed foreign interest/interference in local affairs.
There is a reason racists like Whitestrake hate the book 'Guns, Germs, and Steel'; it lays bare that luck and geography, not racial superiority, are behind most differences in how cultures grow, advance, and interact with the world around them.
