Chattel slavery, as a core component of African economies, did not exist. There was slavery, but it was not inherited, not a major aspect of the economy, and not a motivating factor for development. When Europeans came to Africa, they found States that in many ways put European ones to shame. Benin shocked European explorers with its high culture and developement.

Europe, however, had begun the exponential growth that comes with capitalism. This created industrialized production, more advanced technology, and thus a monopoly on these key goods that could give African States leverage over their neighbors. Europeans took advantage of this, and required slaves in return. Those who resisted were met with naval cannons and European guns.

The reason for this was to aid with the massive labor required for all of the land Europe was stealing in the Americas. Agricultural products needed labor. African countries were made dependent on export of human lives. This created demographic crises and stunted development, after all, how can you develop when your economy isn't focused on productivity but instead on warring with neighbors and exporting your own people? This widened the gap, which then was taken advantage of further by Europeans, resulting in colonialism.

The point isn't that slavery did not exist at all. The point is that it was extremely minor, and not at all the focus of African economies until European capitalists established contact, and forced it if not by advanced technology to trade, then by gun and cannon. Europe even refused to share how to create guns, as this way they could control the flow of weaponry, and de-fang resistance. They controlled who had guns, for what reasons, and to what extent. Replacement parts were monopolized, creating dependence.

This is the ball and chain put around African necks, and what began the balkanization of what were, until Europe's involvement, states that rivaled those of Europe. This is the history European settlers wiped away, trying to manufacture a narrative of "civilizing savages." This is what Walter Rodney debunked.