Re: transitions from a wolf-like creature to a whale? (was Rabbits in the Precambrian)

Stephen E. Jones (sejones@iinet.net.au)
Sun, 29 Aug 1999 08:20:03 +0800

Reflectorite

On Wed, 25 Aug 1999 16:35:46 -0600, Susan Brassfield wrote:

[...]

SB>That series of transitionals was filled fairly recently. A couple of years
>ago the National Geographic did a wonderful spread on the fossil
>transitions from a wolf-like creature to a whale. Complete with photos of
>the fossils.

Unfortunately for the Darwinist propaganda machine, it all turned out to be
wrong! The "wolf-like creature", namely a mesonychid, turned out not to
be ancestral to whales after all, despite all the earlier confifdent
pronouncements.

Now they are back to square one with the putative whale ancestor being
thought to be some unspecified "ungulate" or "artiodactyl" (see the following
extract from SCIENCE of 7 August 1998).

Steve

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Whale-Ungulate Link Strengthens

--
Little old whales. Skulls of 50-million-year-old pakicetid whales, with a 
coyote skull (bottom) for scale.
--

Judged by its DNA, a whale is just an overgrown hippopotamus with an unusual lifestyle. Researchers who learn how living animals are related by studying their DNA have tended to group the cetaceans-whales, dolphins, and porpoises-with the even-toed ungulates, or artiodactyls, which include cows, pigs, and hippos. By some analyses, hippos are the closest living whale relatives. But to paleontologists, who study fossils, that conclusion has long been anathema. Instead, they contend that cetaceans descended from extinct hyenalike mammals called mesonychians. Now the fossil record may be opening the door to a whale-ungulate connection.

At the meeting, Hans Thewissen, a paleontologist at Northeastem Ohio Universities College of Medicine in Rootstown and an expert on whale evolution, described analyses of new specimens of early whales and whale ancestors his team collected in Pakistan. The new specimens weaken the link between the whales and the mesonychians, which was primarily based on similarities in the teeth. But they support the idea that whales are cousins of the ungulates, if not actual members of that group, he reported "I think there is no doubt that they are very closely related to artiodactyls," says Thewissen.

One blow to the mesonychian link came from two specimens of a 50- million-year-old whale, a member of the family Pakicetidae. Analysis by a colleague of Thewissen's, Maureen O'Leary of the State University of New York, Stony Brook, showed that its teeth are not as highly evolved as those of the mesonychians, making it unlikely that whales are the descendants of that group. But on the question of whether the cetaceans are an actual subgroup of the Artiodactyla, as the molecular biologists think, this and other fossil whales don't give a clear answer.

Thewissen says that five morphological features of the early whales, including features of the skull, upper teeth, and feet, are "not inconsistent" with the hippo hypothesis. In particular, the new pakicetid skulls have holes over the eye sockets, known as supraorbital foramina. These features are not known in modern whales but are common to all artiodactyls.

But the last molar on the lower jaw, which has three sections in artiodactyls, has just two in whales. And in artiodactyls, the astragalus, one of the anklebones, has a rounded head and other characteristics that make the ankle much more flexible than it is in any other mammal. Thewissen recently discovered an anklebone from an early whale ancestor that still had legs. It lacks the rounded head, although in other respects it is similar to an artiodactyl astragalus.

Still, Thewissen thinks the morphological evidence, although mixed, opens the door to some kind of relation between the whales and the ungulates. He adds that there is now "considerable doubt" that cetaceans are closely related to mesonychians. That conclusion got a thumbs up from paleontologists at the meeting. For example, John Allroy of the National Museum of National History in Washington, D.C, says pulling the mesonychians out of the picture makes a closer cetacean-artiodactyl link plausible. But O'Leary says "it's [still] difficult to connect hippos with whales in the fossil record."

The molecular camp, for its part, viewed Thewissen's conclusion as just a first step toward ultimate vindication. As Norihiro Okada, a molecular biologist at Tokyo Institute of Technology, put it: "I think paleontologists may discover more [features common to early cetaceans and early hippos] in the near future." DENNIS NORMILE

(Normile D., "New Views of the Origins of Mammals," Science, Vol 281, 7 August 1998, pp774-775) -------------------------------------------------------------------------

-------------------------------------------------------------------- "Our theory of evolution has become, as Popper described, one which cannot be refuted by any possible observations. Every conceivable observation can be fitted into it. It is thus `outside of empirical science' but not necessarily false. No one can think of ways in which to test it. Ideas, either without basis or based on a few laboratory experiments carried out in extremely simplified systems, have attained currency far beyond their validity. They have become part of an evolutionary dogma accepted by most of us as part of our training." (Birch L.C. & Ehrlich P.R., "Evolutionary History and Population Biology", Nature, Vol. 214, 22 April 1967, p352) Stephen E. Jones | sejones@iinet.net.au | http://www.iinet.net.au/~sejones --------------------------------------------------------------------