Earlier quoted context omitted.
Your arguments seem misleading - the existence of anatomically modern humans goes back roughly 200,000 years, but human history , i.e. the era with documented evidence starts with widespread writing that comes much, much later; first samples of writing is from ~5000 BC, but they're sparse enough to not be informative about social practices. The very first documented law codes (2100–2050 BCE https://en.wikipedia.org/w…
What part of those laws that didn't pertain to agriculture (failing to plant/harvest) were about the penalty for raping somebody else's slave. So many measures of grain etc.
It could be a reasonable assumption that the prehistoric agricultural societies had slavery just as early historical agricultural societies, but that the earlier hunter-gatherers, i.e. a major part of those 200,000 years did not have widespread slavery. Well, other than the "intermarriage" with neighbours (often likely not fully voluntarily) which predates modern humans, given the genetic evidence for the partial "assimilation" of neanderthals and other parallel hominids.