Cetacean Evolution (Whales, Dolphins, Porpoises)
Evidence Of Common Ancestry of Cetaceans and Certain Species of Land Mammals
by Edward T. Babinski
(Reviews of several creationist articles that deny such evidence exists.)
REVIEW OF The strange tale of the leg on the whale
by Carl Wieland
The author states, "Pakicetus was claimed to be a 'walking whale' ? yet the type specimen consisted only of jaw and skull fragments." The author's statement is dated. More bones of Pakicetii have been found, and it appears to have been a walking relative of whales.
Also, a lot can be learned from "only jaw and skull fragments." Here's the rest of the story of those fragments: "One particularly baffling fossil was the back part of a 50-million-year-old skull. It was about the size of a coyote's and had a high ridge running like a mohawk over the top of its head, where muscles could attach and give the mammal a powerful bite. When Gingerich looked underneath the skull, he saw ear bones. They were two shells shaped like a pair of grapes and were anchored to the skull by bones in the shape of an S. For a paleontologist like Gingrich, these ear bones were a shock. Only the ear bones of whales have such a structure; no other vertebrate possesses them."
- Carl Zimmer, "Forward Into The Past: The Origin of Whales," a section in Evolution: The Triumph of an Idea "The position of the inner ear bones in Pakicetus are a perfect intermediate between those of land mammals and the rotated ones of cetaceans (Thewissen & Hussain, 1993), not to mention the fact that the tympanic bullae are composed of dense bone as those of cetaceans (Gingerich, et al, 1983)."
"Pakicetids were the first cetaceans, and they are more primitive than other whales in most respects. In fact, they did not look like whales at all, and did not live in the sea. . .Although . . . it is clear that they are related to whales and dolphins based on a number of specializations of the ear, relating to hearing.
In an article from February 1991, National Geographic Magazine reports a scientific team partly funded by National Geographic, and lead by Philip Gingerich (University of Michigan) discover fossilized bones and feet from a whale that lived forty million years ago, in what is now a desert, located southwest of Cairo, Egypt. N.G. asks, "Since the limbs were so tiny, what purpose did they serve?" The team uncovered remains of 243 archaic whales.
"Ichthyolestes. . . and Pakicetus. . . had meat eaters' teeth, but were not genuine canines, having longer, more powerful tails, longer snouts and smaller eyes than dogs. . .The two also have "several strange bones in their ears that occur only in whales," says Hans Thewissen, of Northeastern Ohio Universities College of Medicine in Rootstown, Ohio, one of the fossils' finders."
"The ear of modern whales and dolphins is specialized to listen to sounds underwater. . . The hearing organ of Eocene whales was not specialized as that of modern cetaceans. Instead it represents a compromise of adaptations relating to underwater sound reception and hold-overs of a hearing system used for listening to sounds in air. The eardrum of these cetaceans is more flat than that of their modern relatives, and the external auditory meatus is still present." Scientists have found a lot of fossils that show what the ear was like in Eocene whales."
[The adaptation of the ear bones of these land mammals (for increased hearing and sense of balance under water) preceded the diminution of limbs and other skeletal changes that eventually adapted such critters to the sea.
See Nature, May 9, 2002 -- E.T.B]
And here is a bit of information on the teeth found in these "jaw and skull fragments" of early whales: "The skulls of Eocene whales bear unmistakable resemblances to those of primitive terrestrial mammals of the early Cenozoic. Early [whale] genera retain a primitive tooth count with distinct incisors, canines, premolars, and multirooted molar teeth. Although the snout is elongate, the skull shape resembles that of the mesonychids, especially Hapalodectes. . . Pakicetus (early-mid Eocene, 52 mya), the oldest fossil whale known, had the same skull features as Hapalodectes . . . Molars still have very mesonychid-like cusps, but other teeth are like those of later whales. . .Whale-like skull crests and elongate jaws." [Skipping past Pakicetus and other early whales and going right to Eocetus of the late Eocene, even those whales] which have lost their hind legs entirely, still retained a 'primitive whale' skull and teeth, with unfused nostrils . . . This stage of aquatic adaptation was attained about 15 million years after the first terrestrial mesonychids."
"Living whales have either no teeth or simple pegs. But the teeth of the oldest known whales looked particularly like the teeth of an extinct line of mammals called mesonychids. These animals were hoofed mammals. . . but they had powerful teeth and strong necks adapted for a life of eating meat. . .The teeth of the oldest known whales still resembled those of mesonychids in their general outline, but they were already changing. . . long gouges run along the outward sides of the lower molars. These gouges formed as the whales scraped their molars with their upper teeth. The whales had to have been making only vertical bites, not side-to-side chewing, to form them. There's fossil evidence that later whales, which also had these gouges, fed on fish. That has led to the view that Pakicetus and its contemporaries had already started eating fish or other aquatic animals."
- Carl Zimmer, "Forward Into The Past: The Origin of Whales," a section in Evolution: The Triumph of an Idea
Since the late 1970s professor Phil Gingerich has collected fossil specimens of early whales from remote digs in Egypt and Pakistan. Professor Hans Thewissen, another cetacean evolution paleontologist, is a former student of Gingerich. According to Gingerich, "I grew up in a conservative church in the Midwest and was not taught anything about evolution. The subject was clearly skirted. That helps me understand the people who are skeptical about it. Because I come from that tradition myself." He shares the same skeptical instinct. Tell him that there's an ancestral connection between land animals and whales, and his reaction is: Fine, maybe, but show me the intermediate stages. Like Charles Darwin, the onetime divinity student, who joined that round-the-world voyage aboard the Beagle instead of becoming a country parson, and whose grand view of life on Earth was shaped by close attention to small facts, Phil Gingerich is a reverent empiricist. He's not satisfied until he sees solid data. That's what excites him so much about pulling whale fossils out of the ground. In 30 years he has seen enough to be satisfied. For him, Gingerich said, it's "a spiritual experience." "The evidence is there," he added. "It's buried in the rocks of ages."
-- David Quammen, "Was Darwin Wrong?" National Geographic Magazine, Nov. 2004, p. 31