Cuvier took shelter in Normandy during the most violent periods of the French Revolution and developed his interests in natural history. Geoffroy Saint-Hilaire extended the invitation to Cuvier after hearing of Cuiver's skill in dissecting animals.
Cuvier later engaged in a public dispute with Geoffroy Saint-Hilaire in In , Cuvier replaced Mertrud as chair of animal anatomy at the Paris Museum. Cuvier insisted that the functional parts of animals ought to guide their classification, because animal anatomy displays functional integration—organs work together to function.
The principle prioritized those parts of an organism that researchers thought were essential for its mode of life, such as the nervous system, the circulatory system, and the respiratory system; over those parts that researchers considered subordinate, or secondary, characteristics. Cuvier prioritized function over form in taxonomy. He further advocated for his position with two principles for anatomical studies: the principle of the correlation of parts and the principle of the conditions of existence.
The correlation of parts describes the functional relationships that must exist between organs to produce a viable organism. For example, historian Peter Bowler explains that using this principle, if one were to discover the fossil remains of sharp claws, one could infer that they belonged to a carnivore, and further infer that it would have teeth with the structure necessary to seize and tear up prey. The principle of the conditions of existence reinforces functional integration between parts of animals by further requiring that these parts be in harmony with the animals' environments and their modes of life.
In other words, there must be an accord between the organism, its environment and its mode of life. Cuvier's scientific principles reflect a teleological approach to the life sciences and natural history , influenced by Aristotle and by Immanuel Kant, an eighteenth century philosopher in Prussia. Cuvier's principles led him to classify the animal kingdom into four main classes, or embranchements branches , and also to deny the possibility of transmutation, what was later called evolution , between species.
Before Cuvier, many naturalists and anatomists divided the animal kingdom into two main groups: the vertebrates and invertebrates. Cuvier insisted that the four categories represented natural groups in the animal kingdom, and that individuals in one category could never transform into another category over time.
As a result, Cuvier criticized the contemporary transmutationist theories defended by Jean-Baptiste Lamarck and Geoffroy Saint-Hilaire, who were both contemporaries of Cuvier at the Paris Museum.
Cuvier believed it was contrary to all of his principles to think that an organism could change one part of its structure over time, without any repercussions to its functionally integrated whole.
Based on his principles, if an organism's structure could evolve piecemeal and slowly transform into new forms, as Lamarck and Geoffroy Saint-Hilaire suggested, it wouldn't survive in its environment. Cuvier also studied fossils. Near the end of the eighteenth century, scholars disputed whether fossils represented life forms that no longer existed, or whether—as the Comte de Buffon, at the Jardin des Plantes in Paris, believed—the fossils found in Europe and America represented animals that had migrated to the tropics.
Buffon argued that God would not have let his creations go extinct. In , Cuvier presented a paper to the National Institute of Sciences and Arts in Paris, in which he compared the anatomy of living and fossil elephants, thus proving extinction to be a fact, as the fossil elephants had not been seen by recent humans. In the following years, Cuvier continued to document the extinction of animals such as the giant ground sloth, the Irish elk, and the American mastodon.
Cuvier's research on extinct forms led him to investigate the causes of extinction. It was at the Museum of Natural History that Cuvier stayed and practiced comparative anatomy. Dividing all living organisms into separate categories based on anatomical observation was ground breaking for his time. Cuvier believed that the anatomy of all living species is so specific and crucial to its functioning that animals could not survive a significant change in their anatomy.
Cuvier scoffed at the idea that living members of these fossil species were lurking somewhere on Earth, unrecognized—they were simply too big. Instead, Cuvier declared that they were separate species that had vanished. He later studied many other big mammal fossils and demonstrated that they too did not belong to any species alive today. The fossil evidence led him to propose that periodically the Earth went through sudden changes, each of which could wipe out a number of species.
Cuvier established extinctions as a fact that any future scientific theory of life had to explain. On this score, Cuvier has been somewhat vindicated. The causes may include asteroids, volcanoes, or relatively fast changes in sea level. These extinctions mark some of the great transitions in life, when new groups of species got the opportunity to take over the niches of old ones. Mammals, for example, only dominated the land after giant dinosaurs vanished 65 million years ago in the Cretaceous-Tertiary extinction.
We humans, in other words, are the children of extinctions. Subscribe to our newsletter. Email Facebook Twitter.
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