This is going to sound really bad, this I know but, it's the truth.
Back when the Jews were financing the slave trade and were directly responsible for the importation and sale of slaves/indentured servants to the America's, the slave owners were having an extremely difficult time with the Africans compared to the white indentured servants. 99% of the Africans have never seen something like a shovel or a tool and they were given this shit and were expected to get to work, not knowing wtf this thing is.
The landowners refused to purchase Africans because of the amount of training that was involved in getting these people up to par so, for a while, the Africans were left standing around while the whites were being picked up for top dollar. After a while, the Jews stopped bringing whites over for sale and the only people left were the Africans. The rest, as we say, is history.
whites were smart enough to stay away en masse from a place where there was a 50% chance to die within the first couple years. the religious zealots were the main dudes who didn't give a fuck because they had a 50% chance of being burned for heresy back home so fuck it.
most slaves weren't captured en masse but sold by the more successful rulers. the sahel and the region north of the jungles of the coast were pretty easy living so when some white dudes show up it was too easy for the ruling class to round them up and ship them out so they wouldn't be lazy agitants back home doing the bare minimum collecting some yams and bitching about not being kangz n shiet. no nation ever exports its productive citizens, although particularly back then due to blood feuds and religion they'd ship out some smart people. past the 1400s they essentially stopped evolving socially/technologically. their technology growth was also weak prior as they got some iron shit pretty fast but based on the demands of their society, it was all that was ever needed nor did they ever refine the process. no copper/steel etc. some it was resource driven but they never had the drive to advance cause they had what they felt they needed.
im reading a book about lewis and clark (focused on their expedition ofc) and their account of the pacific northwest natives entails the relative poverty that comes with having your base survival needs easily met - they were pantsless, loved to fuck, and didn't know anything about the area outside theirs nor cared to.
the ethnic densities in that area were also very similar to germany in that the wurtemburgers hated the prussians, the prussians the hannoverians, the hannoverians the bavarians etc., and all in a close area. while germany is unified now, there is still a clear prussian influence just as seen with all unifying elements because they were the most successful. serbia with yugoslavia, virginia in the USA (diluted via immigrants), muscovy in russia, etc. west africa never significantly unified due to being beyond diverse. at least a prussian can speak to a hannoverian living 100 miles away to trade and talk about technological developments, and rapidly learn the local terminology as there aren't many differences. across the niger river you could find a different people with different customs, language, religion, etc. not conducive towards technological/social diffusion. these tribes also tended to only kill ruling males and redistributing lower order males and every woman to work for you. huh sounds like the end goals of revolutionary communism.
ive always wondered how social scientists come to the conclusion that diversity is our strength when you can just go area by area and see wild failures of it. the new world nations are the only exceptions as when you're forced into a boat and have at least a common goal (make some moniez), you'll stick it out together. inherently brazil/usa etc. are going to be multicultural because multiple cultures bled for a land. doesn't mean there isn't nor shouldn't be a social hierarchy within. not too long ago my irish ancestors were beneath blacks - and make no mistake the ways the irish gained social rank in many places went against good order and discipline with regards to a constitutional nation. i think we can all agree no one should "rise up!" (in the social hierarchy) by literally being given it ---> it also makes no sense as that rank gained means another is displaced. that's the antithesis of any merit based system which every strong nation encourages.