If you're going to bring African slaves into this, I hope you all realize the concept of African slavery was radically different from its Americas incarnation.
Slaves typically had more rights.
Slaves typically were not beaten on a consistent basis, if at all.
Slaves were not corralled based on skin tone.
Slaves had more opportunities for freedom and advancement.
Slaves could have children not enslaved.
Slaves typically intermarried with their owner's children.
On that last point, it was often said that the lineages of slave and master so to speak might become so intermixed for one not to remember which was which.
Does this sound at all like American slavery?
So I want you to picture this, you've had your own version of a slave trade, still terrible, still bad, but not as inhumane as American slavery. Europeans at first come to barter for slaves in the usual fashion. So one might say, sure, their slavery must be conceptually the same. But soon, those same Europeans become lustful, and given their advanced weaponry, demand for more slaves deeper into the continent lest they turn the slave catchers into slaves themselves. Stories return of the sort of terrible life slaves lead over in the New World, not to mention the horrid conditions traveling over. What happens then?