The Discovery of Extinction

When comparing fossils of mammoths to bones of elephants from India and Africa, the French naturalist Georges Cuvier noticed that these two species were rather distinct. Cuvier claimed that, unlike the elephants, the mammoths were fossils of species that had actually vanished from Earth a long time ago. These evidences led him to consider the phenomenon of extinction as a fact, further proposing that periodically the Earth went through sudden cyclical changes, each of which could wipe out a number of species.