There have been five major extinction events, each one leading to a profound loss in biodiversity in earth’s history, and there is general consensus that we are in the midst of a sixth. Some of the previous ones took place in the late Ordovician period, some 450 million years ago, when living things were mainly confined to the water. The most devastating event took place at the end of the Permian period, some 250 million years ago. It came perilously close to emptying the earth of life altogether. The most recent — and famous — mass extinction came at the close of the Cretaceous period, 66 million years ago, and wiped out the the non-avian and marine dinosaurs. (see Elizabeth Kolbert, The Sixth Extinction).
The possibility, in fact the inevitability of human extinction informs speculation about the future of humanity in the Anthropocene. Humans seem to be actively reducing their chances for survival as a species. Will their technoscience produce descendants in the form of machines? Will they modify their gene pool sufficiently to thrive in the conditions of a new world?