How Did Elephants and Walruses Get Their Tusks? It’s a Long Story.
The New York Times
A new study reveals how some mammals evolved nature’s most impressive chompers (which are not always used for chomping).
Elephants have them. Pigs have them. Narwhals and water deer have them. Tusks are among the most dramatic examples of mammal dentition: ever-growing, projecting teeth used for fighting, foraging, even flirting.
So why, across the broad sweep of geologic history, do such useful teeth only appear among mammals and no other surviving groups of animals? According to a study published Wednesday in the journal Proceedings of the Royal Society B, it takes two key adaptations to teeth to make a tusk — and the evolutionary pathway first appeared millions of years before the first true mammals.
Around 255 million years ago, a family of mammal relatives called dicynodonts — tusked, turtle-beaked herbivores ranging in stature from gopher-size burrowers to six-ton behemoths — wandered the forests of the supercontinent Pangea. A few lineages survived the devastating Permian extinction period, during which more than 90 percent of Earth’s species died out, before being replaced by herbivorous dinosaurs.
