How far back? Because you know, even the Out of Africa wave displaced and exterminated someone---the Neanderthals. And the neanderthals, as far as we understand, also displaced other humans; Denisovans, or H. heidelbergiensis, or what have you. Yes, at some depth you get to the point where there were no previous sentient natives; but that goes deeper than you think, and the earliest sentient natives were totally exterminated everywhere except perhaps Australia and Oceania. Perhaps.