" And if there were four extinct species, Cuvier declared, there must be others. The proposal was a daring one to make given the available evidence. On the basis of a few scattered bones, Cuvier had conceived of a whole new way of looking at life. Species died out. This was not an isolated but a widespread phenomenon. “All these facts, consistent among themselves, and not opposed by any report, seem to me to prove the existence of a world previous to ours,” Cuvier said. “But what was this primitive earth? And what revolution was able to wipe it out? "

― Elizabeth Kolbert , The Sixth Extinction: An Unnatural History