An addendum to this should be that Africa is a tremendous and extremely environmentally variable continent. The cities were mostly forced to exist at the edges in the less extreme conditions and more or less shared a lot of common history with Europe and the Middle East in the places where they were accessible. Europe in particular loved trading with Africa because it was an excellent source of fineries such as ivory and especially gold in some locations. Anywhere you get trade, you generally get the natrual spread of technology as observant types take note of what equipment to foreigners are using and work to imitate it if it seems effective. The history of Africa being entagled with Europe and the Middle East dates very far back into the histories of the Roman Empire, Carthage and Macedonia.
I suppose a clever race realist could point out that North Africa is white enough to be passing, to the point where people are occasionally born with blond hair and blue eyes, but I don't think that stands for much on its own.
Something interesting that race realists seem to never bring up is how disease totally obliterated the native populations of North and South America. Therein lies actual, verifiable genetic supremacy if not racial supremacy. It just comes from the fact that European society was fucking filthy and African society existed on a continent that to this day still produces the nastiest fucking diseases we've ever encountered. I guess nobody likes to think about the idea that their race rose to dominance just because they sneezed a few too many times.
North africa has some white genetics, from both the roman conquests and from the later islamic slave raids to capture among other things, white women. But overall that percentage is smaller than native american genetics in contemporary north america. This is a bit of an estimation, if anyone has strong sources that say otherwise I'd love to hear it.
Besides it's a bit of a moot point when discussing Ethiopia, because it does not have that same admixture. I don't think it's accurate to put medieval Ethiopia quite on the same level as Europe, considering the incredible difference in buildings left behind when comparing, but it's just as much a mistake to completely discount Ethiopia. They were arguably the strongest most advanced of the african countries.
There is some ground to claim that Ethiopia is the one African country that has never been colonized; yes during the second world war Italy conquered them for 4 years, but that's about it. Italy was also very much dissappointed to discover that although some of the Ethiopian troops were armed with spear and bow (much like Japanese soldiers were armed with swords), they also had field guns, anti-tank guns, machine guns, artillery, anti-air guns.
One of their main problems, apart from having somewhat less modern weapons, was that they didn't have defenses against poison gas, which the italians used liberally.
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As for disease, I'm not sure why you consider that a point against race realism. The diseases had similar effects on different groups. The same diseases that europeans carried had devastated europe before. Should we consider native americans especially filthy because they traded syphillis to europens for smallpox in return?
I suppose you really love Jared Diamond's Gun's Steel and Germ narrative, correct me if I'm wrong. I don't think the factors mentioned in said work had no effect, but he takes such liberties to fit his world view that it's hard to take him seriously, pulitzer prize or not.
I could probably stand to make a lot of money there with this information. I just might do that now that you mention it.
It's such a shame that you have the mentality of hearing about high trust environments and instead of seeing the value of it and trying to replicate it, you seek to exploit it.