title: History of Tibet
context: Some archaeological data suggests archaic humans passed through Tibet at the time India was first inhabited, half a million years ago.[1] Modern humans first inhabited the Tibetan Plateau at least twenty-one thousand years ago.[2] This population was largely replaced around 3000 BC by Neolithic immigrants from northern China. However, there is a "partial genetic continuity between the Paleolithic inhabitants and the contemporary Tibetan populations".[2]
question: How old is Tibet?
answers: twenty-one thousand years ago