This is a recent and, in the long view, abnormal condition. For almost the whole of the human story, the Earth held several kinds of human at once. As recently as fifty thousand years ago — a flicker, in the time-scales this project works in — our planet was home to Homo sapiens in Africa and the Near East, the Neanderthals across Europe and western Asia, the Denisovans somewhere in the vast Asian interior, the tiny Homo floresiensis on an Indonesian island, and another small human, Homo luzonensis, on a Philippine one.
