A fishy story that has no legs

by 

© Ted Daeschler

Tiktaalik fossil

Tiktaalik fossil.

Published: 30 January 2014 (GMT+10)

It’s all so slick in the evolutionary storytelling world, especially with one of its iconsTiktaalik roseae.

Tiktaalik is a fish supposedly 3751 million years old which has been promoted as a transitional fossil in sea-to-land evolution.

Tiktaalik has its own website2 and was even the theme of a song to promote evolution with the repeated line, “tik, tik, tik, tik, Tiktaalik.”3

The Tiktaalik story began in 2004 when University of Chicago researchers found a fossilized skull (not a fully formed fish) in Canada. More remains were found at the same locality on Ellesmere Island in 2006, 2008 and 2013 and assigned to Tiktaalik.

Many features needed for terrestrial existence are simply not present inTiktaalik—Shaun Doyle

On the basis of the finds, a representation of how Tiktaalik may have looked was produced and presented to the world as proof positive of a transitional form in fish-to-tetrapod evolution.

An unquestioning media soon took up the story and heralded the find as another milestone in science.

In 2006, Dr Jonathan Sarfati considered the evidence and pointed out thatTiktaaliks fin was not connected to the main skeleton, so could not have supported its weight on land. He likened the Tiktaalik claims to the hopes evolutionists held for the fin of the then supposedly extinct coelacanth.4

By 2008, Tiktaalik again stuck its head above water after researchers found more of its cranium to examine. They declared it provided further evidence of Tiktaalik being the ‘missing link’ fossil between fish and land animals. CMI’s Shaun Doyle took a look at these claims:

“Many features needed for terrestrial existence are simply not present in Tiktaalik. Because of this, the most important changes in the braincase are pushed to another link that is truly missing. Moreover, it could not have been preparing for the transition to land because evolution is blind; it cannot foresee what will evolve in the future—especially when the raw material for evolutionary change is supposed to come from random mutations.”5

  Piotr Szrek, Uppsala University

Figure 2. Limestone slab from Poland with fossil footprints. (Piotr Szrek, Uppsala University)

Limestone slab from Poland with fossil footprints.

But in 2010, a discovery in Poland shook the claims about Tiktaalik’s place in the evolutionary timeframe. It was of tetrapod footprints dated (using evolutionary assumptions) at 397 million years, 18 million years older6 than TiktaalikDr Tas Walker wrote:

“If four-legged animals existed 18 million years earlier, then Tiktaalik can’t be the transitional fossil it has been claimed to be”.7

This should have been the end for the Tiktaalik story but no-one—apart from creationists—seemed to see a problem, or, at least, admit to it. The media did not pick up on the significance of the timing problem in relation to Tiktaalik apart from an understated observation in a BBC report about the footprints:

“But Tiktaalik lived about 375 million years ago; and although there are slightly older transition fossils, the Zachelmie Quarry tetrapods break the neat and simple timeline.”8

It’s no surprise that Tiktaalik’s chief advocate Neil Shubin, professor of anatomy at the University of Chicago, has continued to plow on with the storytelling anyway. His team has just released another paper9 about Tiktaalik in which they say the discovery of “large” pelvic bones points to the probability of feet and, therefore, further evidence of its place as a transitional fossil.

Already certain of Tiktaalik’s place in the evolutionary story, Shubin and friends decree:

“Antecedents of canonical tetrapod pelvic characteristics are seen in Tiktaalik. Although Tiktaaliklacks a sacral rib connecting the pelvic girdle with the vertebral column, the iliac blade is relatively more massive and dorsally expanded than in fish.”10

This sounds hopeful, except that the lack of a sacral rib connecting the pelvic girdle to the vertebral column is integral for tetrapods to be able to bear their weight on land! This statement clinches the point:

“Although the size and general robusticity of the pelvis is derived relative to other finned forms, aspects of the general architecture of the girdle are plesiomorphic.”11

If four-legged animals existed 18 million years earlier, then Tiktaalikcan’t be the transitional fossil it has been claimed to be—Tas Walker

First, the terms ‘derived’ and plesiomorphic come from the cladistic method of analyzing alleged evolutionary relationships (see Cladistics, evolution and the fossils). ‘Derived’ (or ‘apomorphic’) means a changed state in the organism in question relative to its claimed ancestors. ‘Plesiomorphic’ (or ‘primitive’) means the ancestral state. E.g. in claiming that birds evolved from reptiles, feathers would be the derived characteristic in an alleged transitional form, while the plesiomorphic characteristics would be the reptilian ones (but see Birds: fliers from the beginning). Thus for Tiktaalik, ‘derived’ means tetrapod-like while ‘plesiomorphic’ means fishy.

Thus the above quote can be translated as: ‘Tiktaaliks pelvis is as big as those of tetrapods, but it actually looks and works like a fish pelvis.’ Without the proper pelvic architecture, the girdle and its attached fins cannot bear Tiktaaliks weight on land:

“Plesiomorphic features of Tiktaalik can be interpreted as highlighting a functional difference with limbed forms: the pelvic fin was not capable of bearing stresses and strains as significant as those of Acanthostega and Ichthyostega, nor was the musculature as well-developed for appendage retraction.”

Translated: ‘Tiktaalik’s pelvis works like a fish pelvis and not a tetrapod weight-bearing pelvis.’ So, by the authors’ own admission,Tiktaalik’s pelvis is easily recognizable as a fish pelvis. To put it in less evolution-friendly terms: Tiktaalik was designed to be a fish, not a tetrapod. This also means that what Per Ahlberg once said of Tiktaalik’s pectoral fins applies just as much to its pelvic girdle:

“There remains a large morphological gap between them and digits as seen in, for example, Acanthostega: if the digits evolved from these distal bones, the process must have involved considerable developmental repatterning [emphasis added].”12

In other words, like every other part of Tiktaalik, its pelvis shows that it is a fish.

A favorable media report13 about the latest Shubin paper admits that “scientists have yet to find a Tiktaalik hind fin bone, or any remains that might shed light on the origins of toes,” without realizing how vital those elements are if the story is true.

Shubin’s response is revealing: “The hind fin of Tiktaalik is tantalisingly incomplete.”

He already stated in the paper that, whatever the result, Tiktaalik’s pelvis shows that its pelvic fin couldn’t bear weight on land! So just like the rest of the storytelling on this specimen over the years, the evolutionists have talked the talk but they can’t make Tiktaalik walk.

Perhaps some alternative words can be added to the tik, tik, tik, tik, Tiktaalik song … tick, tick, tick, tick Tiktaalik, times up—you’re just a fish.

 

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Further Reading

References and notes

  1. Other estimated ages reported at 383 Ma and 379 Ma
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