“…in fact the Indians used to kidnap and enslave each other all the time, without needing the example provided by the white adoption of the African custom of slavery.”
Yes. Slavery still exists in some African countries even today! [1]. And, the Indians were notorious for regularly fighting each other in battles — there wasn’t much “peace” between the redskins.
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[1] “Slavery has never been eradicated in Africa, and it commonly appears in African states, such as Chad, Ethiopia, Mali, Niger, and Sudan…” — Wikipedia.