Sunday, April 09, 2006

The squirming continues...

Creationists haven't said a lot about Tiktaalik, and it's no surprise. However, a few responses have trickled out and they more or less run in the same vein.

I thought this was a rather telling remark on Tiktaalik posted over on Dembski's blog. We're treated to an excerpt of the pre-transformation version of the DI's original response that goes:
I especially like Crowther’s last sentence which I present in its original form (bold type included): “There’s a problem with the Darwinist position that runs even deeper than this, however: If Darwinian evolution is an undisputed fact, as its chief defenders routinely claim, why is this fossil find being billed as such an crucial piece of evidence?”
Icing on the cake! I love it!!!
What I love even more is all this rhetoric and absolutely no reference to the actual fossil material. So, I'll take that as meaning that these guys have nothing to say about its transitional status. The real icing on the cake is all this puff and no real substance.

Unfortunately, the media's response to the discovery is not quite the same as the palaeontological community's interpretation of it. Therefore, by responding to these articles, creationists and their ilk are just blowing smoke. The importance of Tiktaalik has nothing to do with proving the fish-tetrapod transition. That's pretty much taken care of by a wealth of data from the past 100 years.

I would support this with a longer statement or references, but creationists are kindly providing the background for this fact by talking about Acanthostega and Ichthyostega as though we used to believe that were transitional forms and now somehow don't. All these clowns are doing is neatly summarizing growing list of "transitional forms" and making themselves look like asses in the process. These taxa are all still very much there, playing a critical role at the forefront of these reports on Tiktaalik:

From Daeschler et al. 2006
Most of the features used to support this grouping, however, are also seen in early tetrapods such as Acanthostega, Ichthyostega and Ventastega.


Tiktaalik retains primitive tetrapodomorph features such as dorsal scale cover, paired fins with lepidotrichia, a generalized lower jaw, and separated entopterygoids in the palate, but also possesses a number of derived features of the skull, pectoral girdle and fin, and ribs that are shared with stem tetrapods such as Acanthostega and Ichthyostega.

From Shubin et al. 2006
The glenoid [shoulder joint] is oriented posteroventrolaterally and partially exposed in lateral view, which is intermediate between the posterior orientation of the glenoid in Eusthenopteron and the lateral orientation of Acanthostega and other basal tetrapods


In both Acanthostega and Tiktaalik the appendage projects ventrolaterally from the body wall.


The endochondral bones [internal bones] of the pectoral fin of Tiktaalik combine features of Eusthenopteron and Acanthostega, and in some aspects are intermediate.

Need I continue?

If these folks had actually read the papers, they would've seen how comparisons with these early tetrapods figure so prominently in how we actually recognize what Tiktaalik is.


Phillipok said...

Here's my take on the theoretical weakness of "Intelligent design" that the Tiktaalik discovery highlights.

1. Evolutionary relationships make up a natural history in which every biological being has biological parents, and new types first appear by modification of previously existing types. This history shows the morphological and genetic intrerrelationships of species in terms of common descent.

2. The missing links in the fossil record are indeed links: you have some idea what they must be like and know where they belong in terms of what came before and what came after. Gaps are an important type of prediction.

3. The researchers that found Tiktaalik did so because they could predict where to look. If they had found fossils of pandas or humans in Devonian era rocks, that would have knocked down the whole evolutionary theory.

4. In "intelligent design theory" the known fossil record is assumed to be nearly complete, gaps and all.

5. The gaps represent abrupt radical differences, not links. There are no natural evolutionary mechanisms that bridge the gaps.

6. The gaps are points at which "intelligent agents" infuse large amounts of genetic information into the biosphere. They thereby create new basic types on the near side of the gaps. The new basic types are thus biological beings that did not have biological parents. (And we need not know the specific process by which this occurs. If this sounds like magical thinking, it is.)

7. Since there is nothing that nothing that causally connects basic types in a unified natural history other than the mind of the "designer," which is unknowable, there is no natural reason why one basic type should first appear when it does. You can have Tiktaalik first appearing after dinosaurs, and dinosaurs first appearing after humans. Intelligently designed natural history has become fragmented and less intelligible.

Phillipok said... is pretty funny.