Baron Georges Cuvier (1769–1832), a French scientist at the National Museum of Natural History in Paris, was the first to propose the idea of extinctions. Around 1800, his work with mammoth and mastodon bones (although they were not labeled as such until later) found in North America led to his theory of extinction. He showed that these creatures recently went extinct, refuting claims that all creatures that ever existed were still alive today and that fossils were just evidence of as-yet-undiscovered species living elsewhere on the planet. Cuvier is considered to be the father of modern paleontology and comparative anatomy. His confirmation of the extinction process led to the study of even more ancient animals—the dinosaurs.