Nov 14 2007

The Judgement of Tiktaalik

Yesterday the NOVA special: Judgment Day, Intelligent Design on Trial, aired on PBS. It was an excellent documentary of the Kitzmiller vs Dover intelligent design trial of 2005. The producers did not attempt false balance, but they did allow the ID proponents to defend themselves in their own words. I think this was very effective, actually. The ID proponents condemned themselves much more than the commentary of others could have. They mostly whined about how they are being treated unfairly, and about the dominance of “Darwinism” in public education.

In the documentary, as in the trial, and as in science itself, the defenders of evolution were able to marshal actual science and evidence. The documentary focussed briefly on one piece of evidence that was not presented in the trial because it was discovered during the trial – making the point that even as the trial was ongoing further evidence was coming in to support the fact of biological evolution. This new evidence was the amazing transitional fossil called Tiktaalik.

Creationists often charge that there are no transitional fossils, and evolution predicts that the fossil record should be chock full of them. The claim is patently false, and stems mostly from a straw man concept of what a transitional fossil would be. (The most ridiculous example of this is Ray Comfort’s crocoduck.) A transitional form is not some incredible monster. In fact all species are transitional, in that they occupy a morphological position between related species. Fossil transitional species may occupy a position between an ancestral species or group and their descendants.

Creationists counter the existence of clear transitional fossils, like Tiktaalik, by saying that evolutionists can’t prove the forms are actually transitional. Archaeopteryx is a bird with teeth (and a lizard-like tail, and reptilian breast bone, etc.), that doesn’t make it transitional between theropods and birds. They completely miss the implication of the existence of Archaeopteryx, and Tiktaalik, and Ambulocetus (transitional between terrestrial mammals and whales) and the many other clearly transitional fossils. That is – evolutionary theory predicted their existence, and their discovery therefore is validation for evolution.

ID proponents know nothing of predictions, because ID does not make predictions. That is primarily why ID is not science – it cannot be tested by making falsifiable predictions.

What is especially cool about Tiktaalik is that the researchers, Edward B. Daeschler, Neil H. Shubin and Farish A. Jenkins, predicted that they would discover something like Tiktaalik. These paleontologists made the prediction that such a transitional form must exist in order to bridge the gap between fish and amphibians. Even more, they predicted that such a species should exist in the late Devonian period, about 375 million years ago.

So they spent several years digging through the earth on Ellesmere Island in Northern Canada, because geological and paleontological evidence suggested that exposed strata there was from the late Devonian. They predicted that, according to evolutionary theory, at this time in history a creature should have existed that was morphologically transitional between fish and amphibians. They found Tiktaalik – a “fishopod,” beautifully transitional between fish and amphibians.

Tiktaalik had limb-like fins, with elbows and wrists, able to partly support it’s weight but not strong enough to walk fully out of the water. He lacked gill supports which gave him a more flexible neck, and he had a stronger rib cage for more support is shallow water. Tiktaalik also shows signs of both gills and lungs.

What do the ID stooges have to say about this? Well, they fall back on the old ploy that you can’t prove Tiktaalik is actually transitional – a real ancestor of a later species. This is true, but completely irrelevant. They even quote mine from evolutionary biologist Henry Gee to make this point. Steve Reuland has the whole story, including Gee’s angry response to the ID crowd for misrepresenting his position.

Evolution-deniers portray the evolutionary interpretation of fossils as “just so” stories – evolutionists just imposing an evolutionary story on whatever fossils they happen to find. Again, what evolution-deniers miss (out of what combination of ignorance and intellectual dishonesty is a true mystery) is that evolution cannot explain any possible fossil discovery, and some discoveries could potentially falsify evolution (horses in the Cambrian strata).

And what Tiktaalik represents is an excellent and well-documented example of the fact that evolution doesn’t just explain what we find but predicts what we should find. Evolutionary theory predicted that something like Tiktaalik should exist in Devonian strata, and it’s discovery is a dramatic and powerful confirmation of that evolutionary prediction.

Kudos to Nova for a fine program and for further exposing the vacuous and transparent nonsense of intelligent design and its hapless supporters.

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