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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Geoffrey Simmons on not knowing the direction of the sun

Geoffrey Simmons, in a never ending series of self-promotional posts, questions the evolutionary processes that led to the ability of plants to grow up:

The pat answer is that prehistoric flat plants decided to compete for more sun. But where did this need to compete arise? How could a limp ground hugger accidentally develop systems to support excessive weight – maybe tons of wood – root systems to support the weight, transport systems to move the water and nutrients up, and defense mechanisms against weather and pests?

Simmons does not buy the pat answer, but it is a perfectly reasonable causation. Imagine a limited area that is overrun with flat plants. Since there is no more area on the ground, any move in the vertical direction is going to yield exposure to more sun. The need for weight supporting structures, transport systems and defense mechanisms simply followed. This would have been obviously brought about by natural selection. The fact that Simmons can’t see this is actually astounding. I guess his billions of missing links, including upside-down wombat pouches, adhesives used by Barnacles and Mussels, and velvet worms, can all be summarized as an argument from personal disbelief.

Simmons ends with a ridiculous analogy. This of course has become a pattern with creationist/IDers. When they can’t really make a good argument that is based on reason and evidence, they appeal to an analogy that is specifically crafted to prove their point.

Did you notice the derogatory statement that plants accidently developed the ability to grow upright? Or how about how plants decided to compete? This wording would not really be used by scientists and is yet another example of an ID proponent trying to win points by making evolution sound absurd. However, Simmons inability to see natural selection in such an obvious place is what is really absurd.

Update:  The skepTick has an alternate (and more funny) view of Simmon’s post.

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.

Upside down on wombat pouches

In a May 20, 2008 post entitled Billions of Missing Links: Wombat Pouches, Geoffrey Simmons writes:

A design must be considered improbable if it is highly functional and durable yet too complex to have come about spontaneously or by intermediate steps.

This is a simple rewording of irreducible complexity, an idea that is being destroyed with increasing frequency in the fields of paleontology and in molecular biology. IDers proclaim that the species we have today are too complex to have come about by intermediate steps. Who are they to decide what is too complex?  It seems like an arbitrary call to me and set up for future arguments using the moving goalposts fallacy. Besides, systems that once appeared too complex to work without individual parts are now able to be simplified. For example, blood clotting, functional eyes, and the complement system.

The “missing link” brought up in this post is the one of the upside down pouch in wombats:

The wombat has an upside-down pouch. Scientists presume, and it makes sense, that position prevents dirt from entering the pouch when the wombat is digging in the ground. Could there have been transitional species with pouches situated sideways, or did the first wombats have to scoop dirt out of their pouches every day?

The author is using a technique to make evolution sound stupid by bringing up a wombat that would have a sideways pouch or that wombats would have to scoop dirt.  Of course the change from right-side-up to upside-down could have simply been in one step.  When a wombat came along with a mutation that led to an upside-down patch, it would have a strong advantage in being able to raise healthy young.

This characterization of the wombat is laughable, yet convenient for IDers. I suspect the example was brought up because it is going to be hard to find intermediate fossils of wombat pouch evolution due to the pouch being made of soft tissue. Since soft tissues don’t fossilize, it will be hard to trace its evolution.  Unfortunately, there have not been any useful fossils found of wombat ancestors.  But then again, present day-like wombats have not been found either, as would have been predicted by ID.