Sometime after 70,000 years ago our species, Homo sapiens, left Africa to begin its inexorable spread across the globe. Other human species had established themselves in Europe and Asia, but only our H. sapiens ancestors ultimately managed to push out into all the major continents and many island chains. Theirs was no ordinary dispersal. Everywhere H. sapiens went, massive ecological changes followed. The archaic humans they encountered went extinct, as did vast numbers of animal species. It was, without a doubt, the most consequential migration event in the history of our planet.