New technologies show Panderichthys and Tiktaalik on the way to living on land

In a recent paper in Nature, Catherine A. Boisvert, Elga Mark-Kurik, and Per E. Ahlberg show how a prehistoric fish, Panderichthys who lived 385 million years ago, had bone structure that resembles animal digits instead of typical fin architecture. It appears that there is some debate among paleontologists as to the when “fingers” first arose and this paper pushed the date back. It had previously been hypothesized that digits arose from an extrapolation of prehistoric fin structure. However, fossil evidence of Panderichthys and similar fish had indicated that they do not have any such digit bones. However, more advanced technology used in this paper has revealed that Panderichthys_BWat Panderichthys does in fact have these features.

The authors used CT scanning and analyzed a largely undisturbed fin (except when it got smashed upon excavation!) to be able to see inside the fossil. Previously, imperfect fossils and the remains of the fish’s scales did not allow researches to see these bones.

These early fish having these fingerlike digits is not wholly unexpected. In fact, the presence of these bones in the closely related lobe-finned fish Tiktaalik pointed in this direction. Furthermore, the presence of certain developmental genes (hox genes) that are involved in digit development in related present day fish nearly predicted it.

Changes in the details of our knowledge of evolution are what makes science the best way to understand the world. The scientists here resolved some contradictory evidence of where early digits arose evolutionary. At the same time, they proved other scientists wrong. There is nothing wrong with this and it shows the strength of the scientific approach.

The Discovery Institute does not see it that way. They believe that scientists are now backpedalling to try fix some imaginary mistake that they say scientists made. Take for instance, Casey Luskin’s blog post from September 26, 2008 entitled: The Rise and Fall of Tiktaalik? Darwinists Admit “Quality” of Evolutionary Icon is “Poor” in Retroactive Confession of Ignorance.

The first point I want to make is that scientists are not at all one cohesive group with the same exact goals. In fact, scientists working on similar subjects are actually competitors. They compete for money, resources, talent, and recognition. In many respects and unfortunately, it benefits one group for a competitor to be proven wrong. So when Luskin takes a quote from one scientist that contradicts what another said, it does not mean that scientists are engaging in “Retroactive confessions of ignorance.”

Besides, when the article published in 2006 describing Tiktaalik as an example of a transitional fossil, they plainly stated that they do not know the state of Panderichthys’ limb structure.  From the article:

Unfortunately, the distal region of the best-known pectoral fin of the elpistostegid Panderichthys is covered by lepidotrichia and the complete distal endoskeleton is unknown

Perhaps Luskin should have actually read the article that he is referring to when making such claims.  The paleontologists were upfront and honest with their ignorance at the time.

So what is the big problem with “Retroactive confessions of ignorance” anyway?  Are scientists supposed to know everything from the beginning? New technologies or even new insights can tell us what we thought we knew was wrong. It can also tell us that there are things that we didn’t know we didn’t know.  Unlike intelligent design/ creation proponents, scientists are willing to change their minds when new facts and ideas emerge.

Getting back to Luskin’s post, he states:

My main observation is this: if Panderichthys is dethroning Tiktaalik as the icon of the fish-to-tetrapod transition, what does that say about all the hype we’ve seen surrounding Tiktaalik? It says that “poor” and “primitive” Tiktaalik was never all it was hyped up to be.

Tiktaalik is still a good example of a transitional fossil, but so is Panderichthys. Tiktaalik has other tetrapod features that tiktaalik_f from NSFPanderichthys lacks (including changes in skull and rib structures) pointing to it being closer to a tetrapod.  However, Panderichthys shows that fish may have evolved digit-like structures earlier than we previously thought.  Both a re important for our understanding and there was no “dethroning.”

Luskin did something semi-unethical in the post with his figure that compares Panderichthys with a “real tetrapod”. I can’t show the figures from the research article here because of copyright issues, but Luskin took two separate figures and put them together to show a comparison. However, the authors already had made a similar figure that compared not only Panderichthys to a “real tetrapod,” but includes a comparison to Tiktaalik and a more fishlike ancestor. I can only think that he did this to highlight differences to the untrained eyes, because the original figure is much more compelling. What makes his argument even more egregious is that Luskin does not show the very similar drawing from the original Tiktaalik paper that showed the fin bones of Panderichthys as large flat pieces.  Of course that would have disproved the whole “retroactive confession of ignorance.”

Of course, as is often the case with Luskin, that was not the only instance of questionable writing in his post.  His post was filled with the usual quote mining.  For example, he quotes Catherine A. Boisvert from a New Scientist article:

it is now completely proven that fingers have evolved from distal radials already present in fish that gave rise to the tetrapod.” Boisvert also praised her findings, stating: “The disposition of distal radials in Panderichthys are much more tetrapod-like than in Tiktaalik

Luskin makes it sound like Boisvert is ignoring the evidence brought to light by the discovery and analysis of Tiktaalik. Is this what she meant by her statement?  Lets see the original quote (emphasis is mine):

“The disposition of distal radials in Panderichthys are much more tetrapod-like than in Tiktaalik,” Boisvert wrote. “Combined with fossil evidence from Tiktaalik and genetic evidence from sharks, paddlefish and the Australian lungfish, it is now completely proven that fingers have evolved from distal radials already present in fish that gave rise to the tetrapod.”

Rather than bore you with more examples of quote mining, I will just finish with a couple questions:  Are there tetrapods located present at this time in history? Do Intelligent Design proponents have a better theory for the presence of these transitional fossils?

hat tip: JLT

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Casey Luskin is wristless

Tiktaalik (courtesy of NSF)

On July 14, 2008, Casey Luskin asks: Tiktaalik roseae: Where’s the Wrist? In this post, Luskin essentially is saying that the recent transitional fossil of Tiktaalik does not have anything resembling a wrist. The trained scientists who published the paper (Neil H. Shubin, Edward B. Daeschler and Farish A. Jenkins, Jr), the scientists that peer-reviewed their work, and countless others who have read the work disagree with him.  Luskin is not a paleontologist and is in no way qualified to determine the structure/function of fossils.  However, it doesn’t stop him from trying in the name of Intelligent Design.

Lets first start by defining transitional fossils. Transitional fossils are fossils that illustrate an evolutionary transition. They can be identified by their retention of certain primitive traits in comparison with their more derived relatives.  In Tiktaalik for example, its “fins” have many bones and a range of movement that are characteristic of both fins and limbs, but can not really be called either.  Luskin does not understand this and keeps going on about how Tiktaalik doesn’t have a wrist.  This false dichotomy of either having a wrist or a fin is at the heart of Luskin’s misunderstanding.

For example, he states:

So when we come to Shubin’s technical analysis, he admits that Tiktaalik does not have not real a “wrist,” but at best he says that it has some bones that foreshadow a wrist. But does Tiktaalik’s fin really foreshadow a wrist, and how closely do its bones resemble a real wrist?”

This ambiguity between a wrist and a fin that Luskin is referring to is the exact reason that Tiktaalik is called a transitional fossil (see above). It has features of both and can’t be accurately described as either. If it was just a wrist, then the ID proponents would say it wasn’t a transitional fossil.  Paleontologists would agree there.  Luskin goes on to state:

In other words, the joints can flex or straighten. Shubin may be correct, but this is nothing special: the same could be said for living fish species that are capable of using their fins to prop themselves up. And they certainly don’t have wrists.

What Luskin is not understanding here is that the bones were in a configuration for propping themselves up out of water. A very big difference.

To sum it all up, Casey Luskin is not qualified to attack the credibility of Tiktaalik as a transitional fossil.  He does not understand or see that this is a transitional fossil that should and does have elements that are related to both.

What does the evidence say to the Discovery Institute?

The subject of today’s post is again about the denial of evidence for evolution by ID proponents. In the June 9th post, entitled: “Are Neo-Darwinists barking up the wrong tree?“, Casey Luskin and Logan Gage describes how some theists, including Stan Guthrie, are now embracing common ancestry. I applaud these people. However, the authors don’t buy it because of a lack of evidence for evolution. He says that we should ask “What does the evidence say?” I have been asking the same question for some time now, but IDers and I do not come up with the same answer.

One of the authors points is that the Cambrian explosion was too fast without any evolutionary precursors for the amount of new phyla seen. However, the Cambrian explosion was not the “geological instant” that it is made out to be. Does 70-80 million years seem like an instant? If you assume a generation to be 3 months, then that gives nearly 300 million generations of animals. Geological instant maybe, but a biological eternity.

Even if you were to accept that the Cambrian explosion was an act of God(Designer), you still have to accept that the creatures in existence back then are no longer around today. Where did all the new animals come from? This little detail seems to be missing from IDers analysis.

scientists have yet to uncover a scrap of evidence to suggest that they functioned as anything but commons fins

I have made this point so many times that I get blue in the face, but lack of evidence is not evidence that it is wrong. I am not too sure what kind of evidence they would want. Not too many pictures taken back then.

Anyway, as far as there not being a scrap of evidence, lets take a look at what the scientists who found the Tiktaalik fossils say about it:

Tiktaalik developed new mechanisms of head movement, respiration and body support that enabled this fish to exploit shallow water and even subaerial habitats. In support of this interpretation, ribs of the type that occur in Tiktaalik augment thoracolumbar rigidity and axial support, functions that are not necessary in an aquatic setting that is deep enough to support the body.

In regards to the fins that they simply dismisses out of hand, the authors point to:

Here we describe the pectoral appendage of a member of the sister group of tetrapods, Tiktaalik roseae, which is morphologically and functionally transitional between a fin and a limb. The expanded array of distal endochondral bones and synovial joints in the fin of Tiktaalik is similar to the distal limb pattern of basal tetrapods. The fin of Tiktaalik was capable of a range of postures, including a limb-like substrate-supported stance in which the shoulder and elbow were flexed and the distal skeleton extended.

I am not to sure how the authors can honestly say that there is not a “scrap of evidence.” Is it an honest mistake? Willful ignorance? Boldface lie?

They then goes on to poke holes in the Tree of Life (TOL) using the same arguments Luskin has used before. Rather than rehashing my criticisms of his analysis, I will just point you here. I do want to point out that Luskin and Gage refer again to a quote from WF Doolittle from June 1999, before the genomic era and the explosion of bioinformatic tools.

Both groups would do well to carefully scrutinize the scientific data and realize that there are good evidential reasons to question universal common ancestry.

Really? I haven’t seem it. All I hear from ID proponents is denial of evidence (read: Tiktaalik) or taking current unknowns as evidence against evolution (TOL).