Europeans and others had practiced slavery before the 15th century, and I am certain that chattel slavery was not invented then, but its spread depended on new conditions.

The forms of slavery that were proinent earlier were less formally dehumanizing than chattel slavery. Slaves must often have been mistreated, humiliated, and made miserable. But they were not legally the same as objects, at least, not in as many instances as after the start of the trans-Atlantic slave trade.

If the European pattern paralelled the African pattern before the 15th century, then slaves would have had a variety of statuses within their communities, depending on the reasons for their bondage and the conditions imposed upon them.

For example, a person condemned to slavery to work of debt may have had a fixed term of bondage. This person would have been expected to produce material wealth for another person, but would not in all cases have been deprived of personal freedoms (control of his or her own body, living quarters and possessions), or be mistreated. If this was a skilled person, especially, the slave-owner’s pragmatic respect for the skills of the slave would have prevented much ill-treatment.

Other slaves would have permanent unfree status, and would have been more likely to suffer abuse. Young Central Europeans were traded abroad as slaves for centuries, even beyond Europe. The pioneering democrats of Athens practiced slavery, of a sort in which the slaves lived in the house with their owners. Some of these slaves would have been expected to provide sexual services, perhaps even as a matter of contract, and others would have been household servants or laborers. Again, their treatment would have varied.

Slavery before the era of chattel slavery was often a punishment for a crime (murder, theft, debt), or a consequence for losing in war. As such, it was often temporary. But chattel slavery was permanent, and formally dehumanizing. In its nature, it relied upon the permanence of the slave’s status. How could a non-person become a person, after all?

Dehumanization made mistreatment (beating, starving, separating from family, murdering, overworking) easier to commit. This must surely have increased as the predominant form of slavery shifted from judicial and social slavery to chattel slavery, and as the scale of slavery increased, beginning in the 15th century.