I'm never moving

Sudan is classified as being in northern Africa, so if that's all you have you should concede

Here's Sub Saharan Africa. Sudan is definitely included, and so is Ethiopia (figured I should Google the Arabic name for the area and it's mostly modern day Ethiopia and some of Somalia) If there's another definition of Sub Sahara that doesn't include those two countries please let me know.

Are you a geneticist? How would you know?

Funny story, I am a genetecist. It's one of the reasons I can't help but be skeptical about most studies linking intelligence very highly with descent due to the lack of good controls. As for how I would know, it would be due to the fact that not a lot of genetic imprint is left. A migration either gets you a nice imprint in a local population where they don't resemble the overall trend (the trend that you can trace the change forward as you move away from Africa) OR it would leave a cultural trend in the form of a slightly different community, architecture, or anything else as those people came back some 20k years after the initial dispersal as per the article.

Do some reading, Great Zimbabwe was founded in the 11th century.

After a quick skimming of the article, it looks like a trade hub that was starting to have an architecture on par with the rest of humanity. The artifacts there look interesting and I would bet that proper excavation would show some innovations exclusive to those people.

Also the only reason it was a hub was because of the gold mines anyway, which reinforces my idea that creating routes across the Sub Sahara wasn't an attractive idea for the ancients and for many after them.

But ask yourself, why weren't trade routes established within Africa?

You establish trade when you have a surplus of goods and demand for other from the outside, if they were going to be provided. If you have enough and you're content with it, or if you're really busy with survival all the time, then you're not going to establish a trade route to the outside. Either that or you move down the river or closer to the northern sea.

Why didn't they evolve complex social systems?

I have no idea. You want to say that they were too stupid to do it, given the context of this conversation so far. There were kingdoms here and there (the one I mentioned which was in most of Ethiopia and possible parts of Sudan shielded many early Muslims as they fled torture in Mecca, twice. It was a recognized kingdom AFAIK with influence as early Muslims did choose it as a safe haven after its king offered safety to them) Maybe it's because the main threat to them was each other and not a common enemy taking them out as a whole, which is why they managed to form alliances and urbanize pretty quickly once outright colonization started coming over.

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