A wide array of animals have tusks, including elephants, walruses, warthogs, hippos, and even the much smaller hyrax, which look like guinea pigs and are about the size of domestic cats. The other thing they have in common is that all are mammals, which begs the question: Why did some mammals develop tusks?
Published in the Proceedings of the Royal Society B, a new, Harvard-led study traces the origins of tusks to an ancient mammal-like species that lived before the time of the dinosaurs and sheds light on how some mammals would go on to evolve this iconic dental trait. (Minor spoiler: They inherited them.)
Dental exams of fossils more than 200 million years old showed that the first true tusks belonged to later groups of a family of creatures called dicynodonts. These distant relatives of mammals were the most abundant and diverse vertebrates on land before the dinosaurs took over. They lived between 270 and 201 million years ago and included a range of animals from tiny, rat-like dicynodonts to elephant-sized dicynodonts that weighed about 6 tons. Each of them had beaks and a pair of tusk-like teeth protruding from their turtle-shaped heads.
But here’s the kicker: Not all of them were actual tusks.
“Some of them were just big teeth that extended out from the jaw,” said Megan Whitney, a postdoctoral researcher in the FAS Department of Organismic and Evolutionary Biology and lead author of the study.