Re: Did dolphins evolve from dogs?

Evolution is nothing more than a statement that living things have changed over time. As such, it is not a scientific theory -- it is a fact. Paleontologists have found fossils of thousands of ancient species that are similar, but not identical, to related modern species. There are scientific theories that try to explain how evolution might occur, but no biologist doubts that living organisms have changed over time.

If you understand that living things change over time, it's easy to see that whales couldn't have evolved from dogs, because whales and dogs are both modern animals, so neither animal can be the ancestral species from which the other evolved. In fact, the oldest known whale fossils are 49 million (49,000,000) years old, while the earliest known remains of domestic dogs are only 12,000 years old. Dogs are much younger than whales! Even the earliest known fossil canids are younger than the oldest whale fossils.

But whales (and dolphins, and all other members of the order Cetacea ) did evolve from a group of doglike animals that were closely related to the ancestors of ungulates like antelope and moose. These extinct animals -- called mesonychids -- had hooves on the ends of their legs, but the shape of their teeth suggest that they were meat- eating and probably predators.

The most complete fossil of an early whale is called Ambulocetus ("walking whale") . It lived in the area that is now Pakistan about 49 million years ago. The paleontologists who found the fossil could tell it was a whale by the shape of its ear bones, but it also had projections on its vertebrae similar to those found in mesonychids, and four well- developed legs. Later whale fossils have smaller and smaller back legs; all that is left of the legs in modern whales is a remnant of their hips buried deep in their bodies.

Print References:
Nowak, R. M. 1991. Walker's Mammals of the World, 5th edition. Johns 
Hopkins Press: Baltimore.

Theiweissen, J. G. M., S. T. Hussein and M. Arif 1994. Fossil evidence for 
the origin of aquatic locomotion in archaeocete whales. Science: 263: 210-
212.

Zimmer, C. 1998. At the Water's Edge: Macroevolution and the Transformation 
of Life. Free Press: New York.