Georges Léopold Chrétien Frédéric Dagobert Cuvier (August 23, 1769–May 13, 1832) was a French naturalist and zoologist. Of humble working class origins, he belonged to a new class of self-made scholars who worked their way to the top of academe. Cuvier was a major figure in natural sciences research in the early 19th century, and was instrumental in establishing the fields of comparative anatomy and paleontology by comparing living animals with fossils. He is well known for establishing extinction as a fact, being the most influential proponent of catastrophism in geology in the early 19th century, and opposing the gradualistic evolutionary theories of Lamarck and Geoffroy Saint-Hilaire.