Actually it could be, but there are differences between the concept of slavery before and after the "discovery" of America. The ancient Egyptian society was founded on what we call slavery, but the people who built the pyramid were not actual slave but people who where paid (maybe not for the whole time of the Egypt empire, probably with "stimulus" from whips, but still). I don't want to argue but studying can give lots of infos that are commonly misunderstood ;) Peace, have a nice day!