There’s a new episode of PBS Eons.  This one is about the walrus, where they came from and how they got their tusks.

The rise and fall of ancient walruses, and how modern ones got their tusks, is a story that spans almost 20 million years. And while there are parts of the story that we’re still trying to figure out, it looks like tusks didn’t have anything to do with how or what these animals ate.