What reasons were African targeted for use as slave laborers?

Any account of the African slave trade where racism plays a causal role would need to explain why

racism appeared precisely during the early modern period. Indeed, through most of their history

Europeans did not regard Africans as more deserving of slavery than any other foreign people.

Ancient Greeks and Romans, for instance, thought of Africans as one among many tribes of

barbarians that could be traded as slaves. During the Middle Ages the image of African kingdoms

was one of unlimited wealth, as befits the land where so much gold originated, not one of uncivilized

savages. And even in the early stages of the Trans-Atlantic slave trade we see that plantation work

was not regarded as only fit for Africans: indentured white servants were regularly used alongside

black slaves. Europeans developed a sense of superiority towards Africans, and eventually towards

the rest of the world, as their global influence increased and it is probable that racism reinforced

their willingness to engage in slave trading. But it was most likely an endogenous reaction, not an

exogenous cause.

Explanation:

it would be that mali has the worst literacy rate than the others