Wednesday, June 23, 2004

The obvious nature of evolution...

My recent evolution-related posts The world goes round and round, and On the one hand highlighted how evolutionary dogma can sometimes drive scientists to make certain assumptions regarding the data they are analyzing. A recent example can be found at the Panda's Thumb in a post titled, Thalassocnus on The Loom, in which we read of an aquatic sloth that adapted to an aquatic lifestyle over the course of several million years. The post links to a more detailed explanation at in a post titled, Taking the Plunge. Carl Zimmer writes about the myriad of so-called transitional fossils we now have for whales or whale-like animals. He states,
All these discoveries have apparently made whales unsuitable for creationist rhetoric. Yes, you can still find some pseudo-attacks on the fossils, but you have to look hard. The more visible creationists, the ones who testify at school board meetings and write op-eds for the Wall Street Journal, don't bring up whales these days. The animals apparently no longer serve the cause. It's hard to distract people from evidence when it can kick them in the face. Whales, moreover, were not the only mammals that moved into the water. Seals, sea lions, manatees, and other lineages evolved into swimmers as well, and paleontologists are also filling in their fossil record. It's fascinating to compare their invasions, to see how they converged on some of the same strategies for living in the water, and how they wound up with unique adaptations...
Notice how the reason we know that seals, sea lions, manatees, etc., all evolved into swimmers is simply because we find fossils that the evolutionist takes to be transitional. Of course, how the transition took place is glossed over (as you'll see). Never mind that large mammals, such as whales, are extremely sensitive to environmental changes and that the chance of species extinction are probably higher than species evolution. Never mind that although whales and seals are both mammals, they have very different morphological qualities - like how they breathe, for one example. Never mind that the changes proposed to go from a land-based mammal to a saltwater-based whale have to occur in an incredibly short amount of time - incredibly short, that is, for chance evolution. Zimmer continues,
In 1995 Christian de Muizon of the National Museum of Natural History in Paris and his colleagues announced the discovery of sloth fossils in Peru dating back somewhere between three and seven million years. The rocks in which they found the bones had formed in the sea; the same rocks have yielded other ocean-going creatures including fish, sea lions, and weird dolphins with walrus-like tusks. The sloths, de Muizon concluded, were aquatic as well. Terrestrial sloths have much longer lower leg bones than upper ones, but the Peruvian sloths had reversed proportions. Manatees and otters also have reversed legs, which suggests that the sloths' limbs were adapted for powerful swimming strokes. The front of their skull was manatee-like as well: its jaws extended out well beyond its front teeth, with a rich supply of blood vessels. Like manatees, de Muizon argued, the sloths had powerful muscular snouts they used to root out sea grass. (emphasis added)
He goes on to detail evolutionary adaptations that supposedly show how the sloths transitioned from land to sea. This is all so obvious isn't it? Yet notice how the theory drives the conclusion:
De Muizon's group have yet to sort out all the differences throughout the entire skeletons of all five species. We'll have to wait for those papers. But there's enough in print now to raise some interesting questions. In whales, seals, and manatees alike, their arms and hands became flippers--stubby, webbed, fin-like limbs. Thalassocnus still had big, long-clawed fingers on its hands. De Muizon proposes that they would have enabled the sloths to hold onto rocks to stay submerged as they fed on sea grass. Manatees don't need to do this because their bones are especially dense; the sloths had not yet acquired this adaptation. It seems that Thalassocnus only traveled part of the way down the road to a marine life before they became extinct. Why they became extinct (as opposed to manatees, for example), is also intriguing. Did something happen 1.5 million to 3 years ago that ruined their home? Perhaps the coastal waters off Peru became too cold. If the sloths had spread further along the coast, they might not have been so vulnerable. Other mammals moved into the water at very restricted sites as well. For their first few million years or so, whales could only be found off the coast of Pakistan. If some Indian volcano had blanketed the neighborhood in ash, we might never have known what a whale looks like. (emphasis added)
That the sloth fossils are transitional is assumed. Therefore, any anamolies in the data is viewed only through an evolutionary lens. Long-clawed fingers, as opposed to arms that turned into flippers, must have a Darwinian explanation. They obviously had not yet acquired that adaptation. Therefore, they only traveled part way down the evolutionary road before time ran out for them. How they traveled down that road is a question that, well... it's obvious, isn't it?

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