One of the stories that inspired bestselling author Susan Casey's new book on the intricate world of dolphins, Voices in the Ocean, is almost too beautiful to be believed. A biologist named Maddalena Bearzi was studying a group of dolphins off the coast of Los Angeles when she noticed something strange. The "pod" (group of dolphins) had just landed upon a herd of sardines. They were about to start feeding when one, unexpectedly, darted off. The rest followed, swimming full speed out to sea. When she reached them, three miles offshore, the pod had a formed a circle - in the middle of it, a girl's floating body. Very near death, the girl had a plastic bag with her identification and a suicide note wrapped around her neck. With the dolphins' help, she was saved. The first dolphins lived on land. It took them 25 million years to adapt to being in the water. Their bodies shrank and their teeth shrank and their brains got big. They did all kinds of shape-shifting evolutionarily. Their brains grew significantly. It's fascinating because scientists don't know why. Most scientists' main guess is that it was due to their changing social behavior. How did the dolphin know the girl was there? That's the big question. They don't rely on vision. I suspect it had something to do with frequency and vibration but of course that's a guess. We don't know. They tend to treat us the way they would treat other dolphins. By themselves, they're vulnerable - to sharks, getting lost, all these things. So when you see dolphins together there is constant touching. They know how to help each other.