How amphibious whales returned to the sea

Millions of years ago, the first animals emerged from their watery habitat to live on dry land. After becoming fully adapted to a terrestrial environment, however, some animals, such as whales, ultimately returned to the ocean. But the evolutionary steps involved in that watery return have long been a mystery. Now, some exceptional fossils — and one really old baby — are shedding some light on how whales went back to the sea.