Like some of y'all were saying, those Indians were just murder with their slaves. The Comanche in 1820 were a large and powerful tribe. They would raid Apache villages in New Mexico, or Spanish settlements near San Antonio, or the American settlements in east Texas. All enemies were all treated equally. Five and six year old boys and girls who were captured, if they were tough enough, were taken back to the Comanche camp in north Texas and adopted into the tribe. A 21 year old female who was captured, had it about as bad as any person who has ever lived. She was a sex slave and would be raped by a half dozen warriors, night after night.
If she made it back to the village alive, she was a slave with fewer rights than a dog. She was forced to gather firewood, scrape buffalo hides, to do the dirtiest work around the camp. Every night banged by a half dozen warriors. And if a squaw got jealous because her husband was spending too much time with the new captive, the squaw would just cut the captive girl's nose off! Or maybe slice off one of her ears. Or a Comanche could just kill a captive adult, with no recrimination. The Comanche slave literally had fewer rights than a pet dog. There were at least a dozen 21, or 24 year old white girls who made it back to American settlements, who had their nose or ears cut off by Comanche squaws. No, you didn't want to be a slave of the Comanche.
And back in the year 800 AD, the Maya would have big ceremonies where slaves, captured in war, would be marched to the top of the pyramid. Laid down on the stone altar, on their backs, the priest cut the heart out of the living slave with an obsidian knife. The Maya would kill 500 slaves in a single day, and the gutters of the pyramid ran red with blood.
I am not making excuses for slavery of negros to pick cotton in Georgia, but, cotton picking slaves had it a lot better than some of the slaves in North America.
