Slavery in Europe was a thing of the past by the year 1400, with some western European populations beginning to fight for better political systems than the serfdom which had replaced slavery. For the most part, slavery in Africa persisted, but it was never the problem it became at the end of the mideval period when Europeans made their way into the continent. It only got worse with time, notably at the beginning of the 17th century when the Carribbean sugar plantations made their rise.
Slaves were sold by Africans to Europeans in exchange for firearms and gunpowder. Most of the slaves were captured in war amongst Africans, and the guns pouring in from Europe were a catalyst to the chaos. Apart from war, kidnapping was another way to obtain people to sell. The extractive nature of African states in this period were such that people’s needs were in the shadow of the profit motive of the oligarchy. One way this manifested itself was in the punishment of crimes. All crimes were punishable by slavery, making for a justice system that was less about justice than profit. State authority naturally came into question under these circumstances, and the chaos wore away the political centralisation of most countries.
Non governmental institutions also lost their integrity as they also pursued riches via the slave trade. Indigenous religious practices became distorted such that religious leaders acquired slaves to sell to Europeans. This is very interesting as it might explain Africa’s move away from indigenous religions toward western religions, but that is a subject for more research on my part.
If African countries had more inclusive political institutions, perhaps trans-saharan and transatlantic slave trade would not have happened. Inclusive political institutions would involve the population in the decision of whether or not it is just for citizens to be transported elsewhere to become slaves, in contrast to the top-down institutions that made it the decision of an elite minority.
If European and American states had more inclusive political institutions, the slave trade would probably not have happened. More inclusive institutions we political privileges would be extended to non-white populations within these countries, hence it is trivial that these populations would not be subjugated to slavery.
Such institutions for the Americas have implications on the effect of the rise in Carribbean sugar production. Instead of the importation of slaves, widespread employment and technological innovation would probably have resulted from the competitive market that would have been. Indeed I make the same assumption for cotton production. The slave trade held back, although clearly not to the same extent, all of Africa, America and Europe considering the potential prosperity that inclusive political and economic institutions would have brought.