Thursday, January 24, 2008

The Tiktaalik Goal Post

This was just too much.  Over on the Discovery Institute webpage, Casey Luskin is trying to explain away the marvelous Tiktallik rosaea find of Niel Shubin and his group.  I guess I shouldn't be that surprised, they usually start grasping for straws when something so convincing comes into play.  This time Luskin uses so many logical fallacies that it is hard to know where to begin.  First he uses a favorite ploy of the ID'ers by moving the goal posts of proof.  Next he sets up a straw man argument by saying that "evolutionists boast about the size of the previously large "gap" in this transition, and how Tiktaalik solves all these previously unanswered questions".  He rounds it all off with the equally fallacious (and equally commonly used by the ID'ers) argument of incredulity.  In other words, he doesn't see how the evidence could fit and therefore it doesn't.

Here we have an ideal example of an animal that shares features of a fish and the first tetrapods (four legged animals).   It had fins scales and gills like a modern fish, but its flat head, neck and ribs were more like similar to those of early tetrapods.  Moreover, the truly amazing thing about the find is that they predicted that it would be there!  The fossil record and molecular evidence suggested that there should be a flat-headed fish in a fossil bed from that time period (375 million years ago), and it was.  This further solidifies the predictive power of evolutionary theory. 

Yet Luskin chooses to ignore all of this beautiful evidence and instead sets up a straw man by saying that evolutionists believe that this answers all of the questions about the fish to tetrapod transition.  I can assure everyone that no biologist thinks this.

Since he has set up this straw man that there is 100% confidence in the field, he then moves on to knocking it down.  He attempts to do so by looking at the fin skeletons of Tiktaalik and the other early tetrapods.  They do not look similar enough to him, so he brushes off the entire find as unimportant since, as he says "I would assume that documenting how fins turned into feet would be one of the more important aspects of the fish-to-tetrapod evolutionary story".  (He also seems, unbelievably, to think that Panderichthys is more similar to the tetrapod skeletons and I really don't know what to say about that.  This is a subjective argument which he tossed in, but cannot really make.  Has he been trained in comparative anatomy?  I doubt it.)  Well, if you can't see the similarities, they must not exist, right?

Well Mr. Luskin, you assume wrong.  There are many fundamental differences between fish and tetrapods, not just that one can walk and the other has fins.  These anatomical features are spelled out very clearly on Shubin's webpage so I won't go into it here.  On top of it all, these differences evolved at different rates.  So yes, there are more fossils to be found that would ultimately show a smoother transition between Tiktaalik and the early tetrapods, but this beautiful  fossil still provides a vast amount of evidence that a transition does indeed exist.

Let's try to be a tiny bit objective (I know, I'm asking way too much her) about this and not make logical fallacy after logical fallacy.  Next time, try making an argument that at least utilizes a few facts, not just your opinions.  As you point out, we will find another fossil in the future that solidifies this transition even more.  But contrary to your statement, we will not claim that we knew vary little about the transition before, nor will we claim to know it all after. As someone smart once pointed out (mockingly towards an ID'er, naturally), every time we find a transition fossil, we create another gap.  But we make the gaps smaller, and we increase what we know by orders of magnitude.  You can't keep moving the goal posts.  There is currently sufficient evidence to show that fish evolved into tetrapods.  But what will it take to convince you?  By paying attention only to the gaps, you are missing the big picture.  You are claiming that a TV show is no good because you watched the commercials.  Not exactly convincing my friend.


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