A Whale of a Tale

The evolution of whales involved much more than legs becoming flippers or vestigial organs. The fossil series demonstrates how their breathing apparatus changed, their ears changed and other body parts changed. If you are interested in detailed taxonomic descriptions, click on an animal illustrated at right to be taken to another website with that information.Whales did not turn into fish. Inside every flipper is found the bones of the mammalian hand. They swim like otters by undulating the mammalian spine. The tail fluke is not a fish fin. Evolution works by modifying existing body plans to fit new conditions of life, and is often constrained by developmental pathways. No longer limited by gravity and strength of bones, whales could become giants of the sea.

Uh, so showing how whales are mammalian and not fish demonstrates evolution, eh?

The team's research, funded by the National Science Foundation (NSF), shows that the semicircular canals, the organ responsible for balance and located in the inner ear, was adapted to aquatic life approximately 45 million years ago. The discovery was published in the May 9 issue of the journal Nature.Cetaceans (whales, dolphins and porpoises) have unique semicircular canals that allow them to be highly acrobatic swimmers without becoming dizzy. By investigating this organ in ancient fossils, the researchers found that early whales acquired this special trait quickly and early on in their evolution. This was a defining event that likely resulted in their total independence of life on land."The early evolutionary development of small semicircular canals by cetaceans opened an entirely new mammalian niche for habitation and contributed to the broad diversity of marine living habits that we see in whales today," said Rich Lane, director of NSF's paleontology program, which funded the research. "The evolutionary acquisition of such specialized organs or abilities (like the brain and upright walking habit of man) provide mechanisms by which highly evolved organisms dominate in certain environments."The semicircular canals sense head movements and this vital information is used to coordinate the body during locomotion. This happens subconsciously, and humans only become aware of an organ of balance when things go wrong, such as during sea sickness, drunkenness and wild roller coaster rides.The researchers found that in living cetaceans the semicircular canals are much smaller than in any other mammal of the same body size. In fact, the semicircular canals of the huge blue whale are smaller than those of humans. In general, cetaceans are more acrobatic than similarly sized land animals (imagine an elephant making the jumps of a similar-sized whale). This could be the result of the small canals, because the small size makes the canals less sensitive, preventing the animal from becoming dizzy (i.e. experiencing vertigo).

Some researchers use morphology (the study of an animal's structure and form) to suggest that whales are descended from mesonychians, an extinct group of meat-eating animals that resembled hyenas with hooves. Others use DNA, molecular, and genetic techniques to suggest that whales and hippos are more closely related to one another than either of them is to any other species.The fossils found in Pakistan last year add weight to the second theory: that whales descended from the group of animals known as artiodactyls, whose members include sheep, cows, pigs, camels, deer, and hippos. Artiodactyla (Greek artios, entire or even numbered, and dactylos, finger or toe) are named for the even number of fingers and toes (two or four) found on each hand and foot.The fossils found by Gingerich and the others are the first and only known specimens that have sheep-like ankle bones and archaic whale skull bones in the same skeletons. Some of the ankle bones have signature features that place the whales in the artiodactyls group.Certain ankle bones show specialized features typically associated with adaptation to running. Such features are unique to artiodactyls, living and extinct.The presence of artiodactyl-like ankles in the primitive whales strongly suggests common heritage rather than convergent evolution, said Kenneth D. Rose of the Program for Functional Anatomy and Evolution at Johns Hopkins University School of Medicine in Baltimore, Maryland. Convergent evolution is the process by which different groups of organisms may evolve similar characteristics in response to particular environmental requirements.

As Stephen Gould concludes, "If you had given me a blank piece of paper and a blank check, I could not have drawn you a theoretical intermediate any better or more convincing than Ambulocetus. Those dogmatists who by verbal trickery can make white black, and black white, will never be convinced of anything, but Ambulocetus is the very animal that they proclaimed impossible in theory."
Natural History magazine, May 1994.

Mr. Madison, what you've just said is one of the most insanely idiotic things I have ever heard. At no point in your rambling, incoherent response were you even close to anything that could be considered a rational thought. Everyone in this room is now dumber for having listened to it. I award you no points, and may God have mercy on your soul.

The terms 'transitional' and 'intermediate' are for the most part used as synonyms to each other. However, a distinction between the two can be made:* Transitional can be used for those forms that do not have a significant amount of unique derived traits that the derived relative does not possess as well. In other words: a transitional is morphologically close (if not identical) to the actual common ancestor of itself and the derived relative.
* Intermediate can be used for those forms that do have a large number of uniquely derived traits not connected to its derived relative.

the story of evo factual claims