Whale Ancestor Possibly Long-Legged, Rat-Like

And the Indohyus? "A tiny little deer maybe the size of a raccoon and no antlers," Thewissen said. He said it most resembles the current African mousedeer, which has a rat-like nose and "when danger approaches, it jumps in the water and hides."

India and Pakistan were the general region where early whales lived. That matches with the Indohyus but not the early African hippos, Thewissen said. While modern-day cetaceans are known to be smart, early whales and Indohyus had small brains, the researcher said.

Other scientists were intrigued, but far from convinced, especially since the case for hippos has looked good, they said.

"While this new hypothesis for the origin of whales is compelling, it will require further testing, especially since other recent studies have suggested both hippos and Raoellids were involved in whale ancestry," San Diego State University biology professor Annalisa Berta said in an e-mail. Raoellids are the larger grouping of species that include the Indohyus.

Kenneth Rose, a professor of functional anatomy and evolution at Johns Hopkins University, said Thewissen didn't provide enough evidence to merit his conclusions. He also questioned the use of the composite skeleton. The ear bone thickness, the key trait that Thewissen used, was difficult to judge and seemed based on a single specimen, Rose said. Much of the work is based on teeth, and overall the remains preserved from this family of species are poorly preserved, he said.

Thewissen said there are problems with not enough well preserved fossils, but he said what's left makes a strong case for Indohyus as the closest land ancestor -- with hippos as the closest living land relative.

Related Links:

How Stuff Works: Evolution

Introduction to the Cetacea

Hans Thewissen's page