Casey Luskin over at the Disco-Tute’s blog is getting all excited about the recent discovery of fossilized tetrapod (four footed vertebrate) footprints in Poland, dated 395 million years ago. What? The Disco-Tute is excited about new scientific discoveries? Well, yes, but only because they think it disproves evolution, or something. Luskin’s post is entitled Tiktaalik Blown "Out of the Water" by Earlier Tetrapod Fossil Footprints, which should give you an idea. Briefly, the transitional (between fish and tetrapod) fossil Tiktaalik was found in rocks 375 million years old, but these new tetrapod fossils are 395 million years old, so this newly discovered tetrapod wasn’t a descendant of Tiktaalik. Luskin claims this means Tiktaalik isn’t a transitional form, even though it clearly has features of both fish and tetrapods (more on that below).
The fossil tetrapod footprints indicate Tiktaalik came over 10 million years after the existence of the first known true tetrapod. Tiktaalik, of course, is not a tetrapod but a fish, and these footprints make it very difficult to presently argue that Tiktaalik is a transitional link between fish and tetrapods. It’s not a “snapshot of fish evolving into land animals,” because if this transition ever took place it seems to have occurred millions of years before Tiktaalik. [My bold.]
Of course, Luskin’s reasoning is wrong – if Tiktaalik is an intermediate between fish and tetrapods, then the discovery that this evolution also occurred earlier doesn’t suddenly magically mean that Tiktaalik isn’t an intermediate between fish and tetrapods anymore. The evidence that Tiktaalik is an intermediate is still evidence that Tiktaalik is an intermediate. Luskin doesn’t understand what an “intermediate” is – he thinks it has to be something on a direct line from (in this case) fish to existing land animals; it’s actually just a fossil that shows evolutionary change within lineages. (It has features of both a fish and a tetrapod, so it shows evolution happening.) Luskin thinks evolutionary theory says this happened only once. But evolutionary theory doesn’t say that. Transitional forms don’t have to be direct descendants of living species, they just have to be transitional between species (“cousins” of our ancestors, if you like) – that is, they just need to demonstrate evolution occurring.
PZ has a good post up, Casey Luskin embarrasses himself again, where he explains that Tiktaalik's status as a transitional form does not depend on us slotting it in a specific chronological time period as a link between two stages in the evolution of a lineage.
Why ID Is Useless
An interesting thing about Tiktaalik, is how Neil Shubin (its discover) managed to find it using a prediction of evolutionary theory. In his post, Luskin quotes Shubin. I’ll repost what Luskin quoted, but I’ll add a piece that he missed, from Zimmer and Shubin on Tiktaalik:
What evolution enables us to do is to make specific predictions about what we should find in the fossil record. The prediction in this case is clear-cut. That is, if we go to rocks of the right age, and the rocks of the right type, we should find transitions between two great forms of life, between fish and amphibian.
What we see when we look at the fossil record, at rocks of just the right age, is a creature like Tiktaalik. Just like a fish, it has scales on its back, and fins. You can see the fin webbing here. Yet when we look at the head, you see something very different. You see a very amphibian-like thing, with a flat head, with eyes on top. It gets even better when we take the fin apart. When we look inside the fin, as in this cast here, what you’ll see is bones that compare to our shoulder, elbow, even parts of the wrist—bone for bone. So you have a fish, at just the right time in the history of life, that has characteristics of amphibians and primitive fish. It’s a mix.
[My bold to indicate the bit that Luskin didn’t quote.]
Tiktaalik is undoubtedly transitional. With gills, scales and fins it is a fish, but its fins, instead of having the many tiny bones normally found in fish, had fewer but sturdier bones in its limbs – bones similar in number and position to those of every land creature that came later. Also, it had a flat head with eyes on the top like a modern amphibian, and it had a neck (which fish don’t have). It also had spiracles (breathing holes) on the top of its head, which suggests it had primitive lungs, and it had stronger ribs that allowed it to pump air into these lungs. Normal fish don’t need these because they breathe through their gills.
Luskin misses the point of all this with his “Tiktaalik, of course, is not a tetrapod but a fish” comment. Typical creationist – scientist finds a transitional form (fish to tetrapod) and creationist insists it’s not transitional because it’s still either a fish or a tetrapod. (Fish, in this case.) Nothing would satisfy Luskin – regardless of what new fossils are found, according to Luskin they’ll either be a fish or a tetrapod but never a transitional.
Also, it is beyond question that Shubin used evolutionary theory to predict where he would find Tiktaalik. He reasoned that if there were lobe finned fish but no terrestrial vertebrates 390 million years ago, and terrestrial vertebrates 360 million years ago, evolutionary theory would predict that you would find fossils of the transitional form in rocks around 375 million old (ie in between the two). And you would find them in a freshwater area, since both lobe finned fish and early amphibians lived in freshwater. So that’s where he looked. And guess what? That’s exactly where he found it. So evolutionary theory predicted where the fossil would be found. Again, this all flies right over Luskin’s head:
The New York Times presaged Shubin's argument, first reporting on Tiktaalik that "the scientists concluded that Tiktaalik was an intermediate between the fishes Eusthenopteron and Panderichthys, which lived 385 million years ago, and early tetrapods. The known early tetrapods are Acanthostega and Ichthyostega, about 365 million years ago." But would neo-Darwinism have predicted true tetrapods from 397 million years ago? Definitely not
No, but then neither would Intelligent Design (ID) have predicted this. The same way that ID didn’t predict Tiktaalik. These new fossils were discovered by real scientist doing real science, not by creationists using “Intelligent Design.” What this demonstrates is that science expands our knowledge while ID is completely vacuous and useless. ID didn’t predict anything (neither Tiktaalik nor these new fossils) since ID is nothing but a bunch of ignorant whining about evolution.
Where do we go from here? Well, clearly the creationists at the Disco-Tute will continue to miss the point entirely and claim that this discovery by real scientists somehow invalidates discoveries made by other real scientists. Meanwhile, actual real scientists will use this new information as a springboard to investigate and learn more. Philippe Janvier from the Museum National d'Histoire Naturelle in Paris (reviewer of the paper on the newly found fossil) told CNN:
"The divergence between the tetrapods and their closest fish relatives is much younger than previously thought and it obliges us to find actual evidence -- skeletons or complete fossils -- in much earlier strata that could enlighten us between this divergence."
Real scientists will now do actual research on these new fossils so we can learn more about our past. The difference between this and creationist poseurs such as Luskin, couldn’t be clearer.
Jerry Coyne’s excellent book Why Evolution Is True has more on Tiktaalik and on transitional forms in general.