Good post.
Also, indentured servants and adoptions of orphans to be used for hard labor jobs was an informal system with the same inhumanity.
Exploited white immigrants in factories as child laborers were shown in a couple of the “giants of industry” documentaries about Andrew Carnegie types. Missing fingers, hands, arms of children who were maimed by dangerous machinery.
My ancestors were “slaves” from Northern Ireland brought here in the early 1700’s. They were euphemistically called “indentured servants”.