They can't exist because they were exterminated in the comet strike of 10,818 BCE. We don't know whether they would have coexisted with us. E.g., hippo populat

They can't exist because they were exterminated in the comet strike of 10,818 BCE. We don't know whether they would have coexisted with us. E.g., hippo population in Columbia is exploding. Megatherium sp. coexisted with hunter-gatherer humans for at least thousands of years. Horses and camels can coexist with humans. They too were obliterated in the Americas by the comet strike. But we anyway know people did hunt all of them, before that.