Blue whales are enormous, magnificent creatures. The largest mammals known to have existed, they can grow to be more than 100 feet in length and weigh more than 100 tons, and they don’t even have teeth.

They capture prey using a giant sieve in their mouth of baleen or whalebone.

Made of keratin, like fingernails, baleen allows whales to swallow large amounts of food while filtering out seawater.

At one time, however, baleen whales did have teeth. Now, scientists have found the first genetic evidence for the loss of teeth in the common ancestor of all baleen whales.

The research appears in a recent issue of the Proceedings of the Royal Society B: Biological Sciences.