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Slavery existed in the world since biblical days, across all of Mesopotamia, Africa, even Asia. From Greek to Romans to you name it. And even in the Americas, slavery existed in the Native American cultures, MesoAmerica, etc..
It's actually quite abundant.
And if you really want to get technical? American slavery was an "adopted" Angolan custom. Yup, it was brought over by black Africans. The 1st American slave owner was in fact a black. He "sued" for the right of his custom in the US Supreme court, which sided with him and allowed the 1st slave in America.
This is why I say, "do some research." You'll be surprised at how different the actual truth is from the general hearsays of this uneducated generation.