The Sixth Extinction: An Unnatural History by Elizabeth Kolbert:
Cuvier’s job at Paris’s Museum of Natural History—the democratic successor to the king’s cabinet—was, officially, to teach. But in his spare time, he delved into the museum’s collection. He spent long hours studying the bones that Longueuil had sent to Louis XV, comparing them with other specimens. On April 4, 1796—or, according to the revolutionary calendar in use at the time, 15 Germinal Year IV—he presented the results of his research at a public lecture.
Cuvier began by discussing elephants. Europeans had known for a long time that there were elephants in Africa, which were considered dangerous, and elephants that resided in Asia, which were said to be more docile. Still, elephants were regarded as elephants, much as dogs were dogs, some gentle and others ferocious. On the basis of his examination of the elephant remains at the museum, including one particularly well-preserved skull from Ceylon and another from the Cape of Good Hope, Cuvier had recognized—correctly, of course—that the two belonged to separate species.
“It is clear that the elephant from Ceylon differs more from that of Africa than the horse from the ass or the goat from the sheep,” he declared. Among the animals’ many distinguishing characteristics were their teeth. The elephant from Ceylon had molars with wavy ridges on the surface “like festooned ribbons,” while the elephant from the Cape of Good Hope had teeth with ridges arranged in the shape of diamonds. Looking at live animals would not have revealed this difference, as who would have the temerity to peer down an elephant’s throat? “It is to anatomy alone that zoology owes this interesting discovery,” Cuvier declared.