Since Gingerich's finds, he and others have filled in more of this fantastic story. Scientists now think the earliest ancestor to whales, was similar to this 50 million year old wolf-like mammal called Sinonyx.
Sinonyx was a predatory scavenger that lived and hunted along the shores of an ancient sea. Perhaps its descendents found the water a source of abundant food and a haven from competition.
Over millions of years front legs became fins, rear legs disappeared, bodies lost fur and took on their familiar streamline shape.
Since Gingerich's first find named Pakicetus, the list of known transitional whales has grown. It now includes Ambulocetus, Rodhocetus, Durodon, as well as Basilosaurus.
They reveal another element of whale evolution. The gradual migration of nostrils to the top of the head, as whales adapted to breathing in the water.
All images and extracts from NOVA, WGBH Boston, PBS Television |