[Update 6/16/09: Quote in paragraph 4 clarified to make it clear that the quote did not come from Dr. Catherine A. Boisvert but was rather stated by the journal The Scientist. Any prior lack of clarity on the author of that quote was completely unintentional.]
Over the past couple years, Tiktaalik, a fish-fossil touted as documenting key aspects of the transition from fish to 4-legged tetrapods, has become a new celebrated icon of evolution:
- PBS’s “Judgment Day: Intelligent Design on Trial” featured Tiktaalik as their premier transitional fossil (an anachronism since the fossil wasn’t even reported until months AFTER the Dover trial concluded).
- The National Academy of Science’s 2008 “Science, Evolution, and Creationism” booklet also prominently features Tiktaalik, pushing it as “a notable transitional form.”
- In early September, Carl Zimmer was so eager to mention Tiktaalik as a fossil that “illuminates our ancestors’ transition from sea to land,” that he plugged it in a New York Times article about a video game that had absolutely nothing to do with Tiktaalik.
Clearly, Darwin’s public relations team has invested much rhetorical capital into this fossil. If past experience is to be our guide, the only event that might cause Darwinists to criticize Tiktaalik would be the publishing of a fossil that was claimed to better document evolution. In the past, I have called such events, evolutionist “retroactive confessions of ignorance.” And with a recently published re-analysis of the fish Panderichthys, Darwinists are now praising Panderichthys for having features that are “much more tetrapod-like than in Tiktaalik,” and are retroactively confessing weaknesses in their precious Tiktaalik, which is now admitted to be a fossil with a “quality” that was “poor.”
The latest retroactive confessions of evolutionist ignorance comes on the heels of a published re-analysis of the bones of Panderichthys. The study used CT scans to show Panderichthys apparently had a few well-defined radial bones in its pectoral fins. (Radial bones are found only in fish fins, but evolutionary paleontologists contend that radial bones are homologous to digits in tetrapod limbs.) When commenting on this new find, the paper’s lead author, Catherine A. Boisvert, boasted in an interview with The Scientist that “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.”
Confident that Panderichthys fossil showed evolution better than Tiktaalik, Darwinists then proceeded to admit striking criticisms of Tiktaalik: The Scientist article stated, “Previous data from another ancient fish called Tiktaalik showed distal radials as well — although the quality of that specimen was poor. And the orientation of the radials did not seem to match the way modern fingers and toes radiate from a joint, parallel to each other.” (emphasis added)
The “quality” of Tiktaalik as a fossil specimen was “poor”? When did we see evolutionists admit this previously? Never. They wouldn’t dare make such admissions until they thought they had something better.
Moreover, now that we have Panderichthys, evolutionists are openly admitting that the orientation of Tiktaalik‘s radials do “not seem to match the way modern fingers and toes radiate from a joint.” That’s a good point, but it’s old news for readers of ENV: in August, I observed that Tiktaalik‘s radial bones could not be likened to tetrapod digits unless you “[d]ramatically repattern, reposition, and transform the existing radials by lining them up, separating them out.”
And now we must turn to Panderichthys. How convincingly “tetrapod-like” are its newly reported radial bones? Below is a picture comparing the radial bones in the fin of Panderichthys to the digits of a true tetrapod limb:
(Adapted by permission from Macmillan Publishers Ltd: Nature, Catherine A. Boisvert, Elga Mark-Kurik, & Per E. Ahlberg, “The pectoral fin of Panderichthys and the origin of digits,” Figs. 2c and 3d (Sept. 21, 2008); all text but radius (R), ulna (U), and ulnare (Ure) bone labels added by me.)
To my eyes, there’s not much of a comparison to be made. In fact, as reported in a National Geographic (NG) news article, not all evolutionary paleontologists are convinced that these bones were the precursors to real tetrapod digits:
Michael Coates, an evolutionary biologist at the University of Chicago, called the new findings “intriguing” but is not convinced that the digit-like structures in Panderichthys’s fin are the equivalent of our fingers.
For one thing, they seem unusually flat for radial bones, Coates said.
“Radials are generally cylindrical. When you look at [a] cross-section [of the digit], they’re dumbbell-shaped.”
The structures are so peculiar, they might just be fragments of damaged bone, he added.
The extremely un-radial-like and un-digit-like flat shape of these bones can be seen in the CT scan from the paper below:
(Adapted by permission from Macmillan Publishers Ltd: Nature, Catherine A. Boisvert, Elga Mark-Kurik, & Per E. Ahlberg, “The pectoral fin of Panderichthys and the origin of digits,” Fig. 2d (Sept. 21, 2008))
Given the jagged and “peculiar” shape of these “radial” bones in the scan seen above, and the fact that they are flat like the other nearby bones in the fin, Michael Coates makes a good argument that these alleged radials are really just “fragments of damaged bone.”
In the same NG article, one of the paper’s co-authors Per Ahlberg said that if Tiktaalik were to remain the form that is closer to tetrapods, then “finger development took a step backward with Tiktaalik, and that Tiktaalik’s fins represented an evolutionary return to a more primitive form.” In other words, at least some the alleged similarities to tetrapods found in these fossils do not actually represent features that are homologous to tetrapods, i.e. they are convergent similarities, also called homoplasies. This means that similarities between these lobed-finned fish fossils and tetrapods imply homology, except for when they don’t, making the Darwinian rationale for inferring “homology” appear weak and arbitrary.
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.
The problem with making too many retroactive confessions of ignorance is that sometimes they contradict one another. For example, when Tiktaalik was reported, Darwinists attacked Panderichthys as being un-tetrapod-like, stating:
Panderichthys possesses relatively few tetrapod synapomorphies, and provides only partial insight into the origin of major features of the skull, limbs and axial skeleton of early tetrapods. In view of the morphological gap between elpistostegalian fish and tetrapods, the phylogenetic framework for the immediate sister group of tetrapods has been incomplete and our understanding of major anatomical transformations at the fish-tetrapod transition has remained limited.
(Edward B. Daeschler, Neil H. Shubin, and Farish A. Jenkins, “A Devonian tetrapod-like fish and the evolution of the tetrapod body plan,” Nature, Vol. 440:757-763 (April 6, 2006).)
Now that Panderichthys is back in vogue, they are attacking Tiktaalik as a fossil of “poor” quality with radials that “did not seem to match the way modern fingers and toes radiate from a joint, parallel to each other.” But with Tiktaalik dethroned, it seems that there are many reasons to critique its would-be successor, Panderichthys.
Darwinists are famous for making retroactive confessions of ignorance, where they only admit how poor the evidence was for a given fossil transition after some new fossil (which supposedly better demonstrates evolution) is reported. Darwinists have used this approach multiple times in the past when discussing the alleged fish-to-amphibian evolutionary transition. (For example, please see here or here.) This behavior should leave critically thinking readers asking two questions:
- What admissions of ignorance aren’t they making about the transitional fossil du jour (in this case, Panderichthys)?, and
- How strong is the evidence for this evolutionary transition, really?
(Updated, 9:30 am PST)