This isn't an excuse or justification for slavery. This is an explanation of how it happened and how we can avoid future problems.
Slavery started in Africa because people started in Africa. Maybe the Garden of Eden was in the Middle East, but, I think it more likely the Garden of Eden was in Africa. In any case slavery started where people started. Slavery has not ended.
The big attraction in the Americas was land that could be used for agriculture to feed the growing populations of Europe. Yes, cotton and tobacco became important cash crops and I won't argue about the necessity of feeding Europe. In any case the big draw in the Americas was agricultural land.
There wasn't any machinery. There were no itinerant pickers. There was no seasonal labor force. Lots of land and very few people to work it.
At first the people who wanted to grow a crop tried to use indentured servants. That didn't work so well. The indentured servants worked a few years and then went off to get their own land which created an exponential need for people to plant and harvest crops.
It takes a certain kind of risk taking behavior to leave behind everything someone knows and travel to someplace that one knows almost nothing about. That risk taking behavior is probably hereditary. There is something passed from parents to children that encourages aggressive, risk taking behavior. Some kind of predisposition to aggressive, risk taking behavior.
Somewhere along the line someone figured out they could buy slaves in Africa and sell them in the United States. Slavery had been going on in Africa a long time. The people in Africa were used to the ideology of slavery. People became slaves, if they didn't like it they ran away and found their way home. Native Americans or Indians had similar systems of slavery. The advantage of African slaves was that they had no where to run to.
There is another issue too. Just as aggressive, risk taking behavior is probably hereditary submissive behavior is probably hereditary. The aggressive risk takers in the African populations were killed off.
So how do we avoid the mistakes of the past in the future?
Pretty simple, we do not take away the civil rights of people just because there is some perceived benefit.
Any attack on the civil rights of a people, any removal of civil rights from a people creates a slippery slope which can only lead to oppression.
We justify treating people badly,we justify stratification of society, we justify oppression.
There are billions of reasons to justify the oppression of people and I can argue them all. I can argue against homosexuality dozens of ways. I can argue racism and ethnocentrism. I can argue against allowing people whose intelligence is insufficient to vote. I can argue for almost anything I find repugnant.
There is only one reason I can use to argue against oppression or discrimination. It's wrong. Oppression, the violation of a person's civil rights, is wrong.
It's wrong when Anonymous does it. It is wrong when Jullian Assange does it. It is wrong when Andrew Jackson did it. It is wrong when Joe Biden does it. It is wrong when I do it.
Violating people's civil rights is just wrong and stupid.