system
A chat on subreddit /r/NoStupidQuestions
human
in some countries it was outlawed for the locals even 200 years before that (unfortunately they did not count it for the colony). Theoretically outlawed in 1315 as well as serfdom in France (some harbor and places still had it in the south), and completely in France metropolitan in 16xx - but continued in colonies.  1794 outlawed in colonies too but reinstated by napoleon until 1848 I think ? 

If you count the metropolitan area it was outlawed in n14th centuries and people were well aware it was horrible at all points in history.
gpt
Well to get really technical about it, the USA didn't even have slavery until 1662 with John Casor.  


We had indentured servants until then.  And those included whites and blacks.  Many of my ancestors were brought over in the 1630's as white indentured servants.  Obviously, I imagine they were treated better than black indentured servants, but the point is that blacks or whites, they could eventually earn their freedom until 1662.  


1662 rolled around and a guy named Anthony Johnson, himself a black Angolan who'd been an indentured servant himself and had earned his freedom and had a servant named John Casor, decided to simply not fulfill his end of the deal.  The deal was, John Casor did so many years of work, and Anthony Johnson would set him free.  The indenture was a kind of contract.  But after he fulfilled his side Anthony Johnson was like "meh, thou is mine now, bitch.".  


There was a lawsuit which Anthony Johnson lost... Then he countersued and won.  


There was a previous slave named John Punch back in 1630, but only as he was a criminal and that was his punishment.  Nobody had to worry about being enslaved for life other than if they committed crimes until 1662.  


So, over 50 years of European settlement in the Americas before slavery became part of society and law.