It seems like west africa had decentralized urban centers. Since a lot of the these towns did become pretty big. But it seems that it was incredibly diffuclt to actually built a centralized kingdom. I can't rember where I read this but somebody brought up how even the Moroccans who invaded the songhair failed to establish any centralized kingdoms and maintain control. Somethings about the geography just makes difficult .One thing i also noticed they try refer to African ethnic groups or tribes as kingdoms, when there is no evidence of it. They were just small tribal federation, which were extremely savage.
Most of the “west African imperial system” doesn’t have evidence of it being a state of any form but more chiefdoms as there no evidence of a clear and structured hierarchy system, a government that controlled the land and a writing system, there’s no evidence of cities in most these supposed civilizations.
So the Sokoto caliphate and touklour probably represented a significant shift.
It's interesting how Fulanis trace their origins in North Africa.
What is also weird to me is that they are described as pastoralists but they didn't adopt the camel, but only use cattle. Which makes me think they didn't engage in long distance trading or the camel caravan. It might mean that were more localized and not cross regional.
To your point about mali. Yeah I've grown very skeptical since it seems extermly weird that they apparently had massive gold mines . But they never minted a single currency. It sounds very strange. Even the swahili towns which are much smaller when they hit a certain level of development and welath began miniting coins. Also thr lack of an identitfiable capital. As well as the fact that the mandinka lanaguge was not written down which is normally what empire do. Just like the persians and the arabs created a written administrative langauge for the empire.