It’s been well-established that whales descended from terrestrial mammals, but who was this land-dwelling ancestor? Science has unearthed the surprising answer.
Although a series of intermediate fossils have been identified, documenting the evolutionary transition from land to sea, the specific identity of the whales land ancestor was unknown…until now.
Little Water Deer the Granddaddy of Whales
Recently J. G. M. “Hans” Thewissen, Ph.D. and colleagues at Northeastern Ohio University established that Indohyus, an approximately 48-million-year-old deer-like ancestor to be the closest known fossil relative of whales. In the November issue if Nature, Dr. Thewissen’s team elaborates on the telltale similarities between whales and Indohyus that are evident in the skull and ear that reveal the family relationship.
And Indohyus was not just your average little deer. Like hippos, Indohyus spent much of its time in water. This was extablished when the bones of Indohyus were found to have a thick outside layer, a characteristic often seen in mammals that have a semi-aquatic lifestyle.
Ancelstral Whales Entered the Water as Herbivores
Before Dr. Thewissen’s illuminating work, it has been widely assumed that whales descended from a carnivorous terrestrial ancestor, and whales became aquatic to feed on ocean-dwelling fish. However, Indohyus is a plant-eater, and already aquatic, suggesting that the dietary shift to carnivore came after the ancestral whale habitat shift to the water.
More Information
For more information on this discovery, see the original article in the November 2007 issue of Nature or the write-up in Science Daily. To learn more about evolution in general, see the website Science Prof Online or the Suite101 articles Evolution As Theory & Fact, Evolution & Natural Selection,or Natural & Artificial Selection.
