I suspect the Roman tradition of slavery was much less brutal than the American chattel slavery we might be more familiar with. Out of the Roman republic/empire, there are numerous stories about slaves who become poets, authors, adopted sons/daughters with full rights, philosophers, etc.

A quick example, Epictetus was born a slave, but was sent to study philosophy by his master under the tutelage of Musonius Rufus. What kind of minds did the US system of slavery develop over the 200+ years it existed? Frederick Douglass is the only one that really comes to mind, and he succeeded in his intellectual development despite his masters trying to stymie him at every step.