There's a reason people compare garbled voicemails to listening to someone talk underwater—our ears just aren't built for a watery world. But animals like whales and dolphins use sound all the time to hunt down dinner or to serenade a mate. Now, new research is highlighting just how marine mammals evolved to listen underwater.

Whales and dolphins had land-based ancestors that made their way into the ocean millions of years ago. Part of that transition involved modifying their ears so that they could clearly hear sounds underwater and tell where they were coming from, says Nick Pyenson, curator of fossil mammals at Smithsonian's National Museum of Natural History in Washington, D.C. (Read about whale evolution in