Tetrapods from Poland Trample the Tiktaalik School of Evolution Tas Walker
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Countering the Critics Tetrapods from Poland trample the Tiktaalik school of evolution Tas Walker Tracks of tetrapods discovered in a quarry in Poland have been dated many million years earlier than the transition from fish to tetrapod is currently believed have occurred. This requires a radical reassessment of the timing, ecology and environmental setting of the fish-tetrapod transition. The initial reaction of the paleontological community has been to accept that the transition occurred earlier than previously thought. However there are a number of other options that could possibly explain the conflicting evidence without causing such an upset to the existing models and these are likely to be pursued by some paleontologists. Another possibility is that the evolutionary interpretive framework is wrong but this is not likely to be considered. racks of footprints found in a quarry in Poland have At first glance the evidence does not look very Toverturned current theories about how fish evolved impressive. The tracks are preserved as shallow indentations into land animals.1 For years there has been a detailed on the surface of large limestone slabs from Zachelmie evolutionary scenario, involving a number of fossil finds, Quarry in the Holy Cross Mountains of Poland. The rough about how fish evolved four legs and came out of the ocean surfaces have an array of roundish indentations arranged onto the land (figure 1). Probably the most famous fossil in lines (figure 2). But, with the use of lines and diagrams in this sea-to-land icon of evolution is Tiktaalik roseae, (figure 3), the authors have argued a strong case that these a fish with fins that was claimed to have had features indentations are indeed trackways of four-legged animals intermediate between fish and tetrapods. Creationists that resembled large lizards. They were even able to show consistently rejected the evolutionary claims about the the shape of the foot within some of the individual prints and identify the toe marks (figure 4). From the dimensions fossil and showed that it had nothing to do with any of the prints they concluded that some animals were more alleged sea-to-land transition.2,3 All the same, evolutionists than 2 m long. continued to promote Tiktaalik to the general public and 4 These trackways are a remarkable find, but tracks are the popular culture vigorously. It has its own website, not particularly unusual in the fossil record. Thousands features in evolutionary diagrams (e.g. figure 1), stars on of trackways of land animals have been found in many 5 the covers of books about evolution and was even the different locations all over the world. What has captured theme of a song to promote evolution.6 Richard Dawkins, world attention is that that these tracks are “dated” at 397 in his latest book The Greatest Show on Earth, claims Ma, which makes them fully 18 Ma older than Tiktaalik “Tiktaalik is the perfect missing link—perfect, because (within the evolutionary dating scheme8). If four-legged it almost exactly splits the difference between fish and animals existed 18 Ma earlier, then Tiktaalik can’t be the amphibian, and perfect because it is missing no longer.” transitional fossil it has been claimed to be. Effectively But now this footprint evidence from Poland mean it has now become an evolutionary dead end along with that Tiktaalik and all its companion fossils are irrelevant all the other fossils connected with it. In other words, all as transitional fossils. From being stars of the show they those cladograms and other evolutionary illustrations that have suddenly become an evolutionary dead-end. So the vividly displayed the transition from fish to four-footed creationists were right all along.7 animal ancestor (such as figure 1) are incorrect and need to be abandoned. A total upset This is not some small correction or a minor detail. It overturns all the claims that had been established over several decades about a host of fossil discoveries. Something of the magnitude of the upset can be gleaned from statements made about the find. • “They force a radical reassessment of the timing, ecology and environmental setting of the fish-tetrapod transition, as well as the completeness of the body Graphic by Dave Souza, <www.wikipedia.com> fossil record.”9 Figure 1. This neat fish-to-animal transition has been transformed • “[It] will cause a significant reappraisal of our from an evolutionary icon into an evolutionary dead-end. understanding of tetrapod origins.”10 JOURNAL OF CREATION 24(1) 2010 39 Countering the Critics • “[They] could lead to significant shifts in our In fact, that is exactly the line that palaeontologist knowledge of the timing and ecological setting of early Ted Daeschler from the Academy of Natural Sciences, tetrapod evolution.”11 Philadelphia, Pennsylvania, has taken. He pointed out • “We thought we’d pinned down the origin of limbed to National Geographic News that tracks and trackways tetrapods. We have to rethink the whole thing.”12 are notoriously difficult to interpret with full confidence • “That’s surprising, but this is what the fossil evidence and said he’s awaiting more evidence before abandoning tells us.”13 existing explanations for the transition.7 • “These results force us to reconsider our whole picture of the transition from fish to land animals.”14 Are the tracks dated too old? Note the terms “radical reassessment”, A second option that may look attractive concerns the “reappraisal”, “surprising”, “reconsider … whole picture” dating of the tracks. Are they really as old as claimed? and “rethink”. The popular media gives the impression Is there something wrong with the dating? Ideally, that paleontologists are objective researchers who read the story of evolution from fossil record in the rocks, much it would be good if the tracks could be dated some 20 or like reading a book. Creationists are portrayed as being 30 million evolutionary years later. This would mean that biased and unscientific because they interpret the evidence the evolutionary transitions that have previously been from a biblical perspective. They are often accused of established as well as the current evolutionary scenario working by faith and not evidence. Well, this Polish upset could be retained intact. demonstrates that evidence does not speak for itself. It If the dating had been carried out by some isotopic takes thought, ingenuity, mental exercise and interpretation method (e.g. Argon-Argon or Rubidium-Strontium) to make sense of it. We have seen that paleontologists have there would be many avenues by which the date could be admitted that it is going to take some time to rethink their challenged and dismissed, such as appealing to an inherited evolutionary scenarios. age, excess argon, open-system behavior, contamination What are some of the options that they may pursue? or sampling error.15 However, isotopic dating was not It is well known that all scientists come to the evidence used on the limestone because it is not suited to that sort with their own beliefs, biases … and vested interests. It will of method. be especially awkward for those who have invested their The “securely dated” dates referred to were assigned lives and careers in the current fish-to-land animal scenario. from the conodont fossils, Bipennatus bipennatus montensis Another problem is that, at this stage, there is nothing to (Weddige, 1977), found in nearby strata (figure 5).16 From replace the transitional sequence with. their fossil content the rocks were Here are some of the options that may classified as the Eifelian stage of be under consideration together with the Devonian system, and the dates an assessment of their implications for this stage have been assigned and feasibility. by the International Commission on Stratigraphy as between 391.8 Are they really tracks? and 397.5 Ma.17 Once the rocks One obvious question to consider have been classified by the fossils is whether the impressions in the rocks the absolute “dates” are obtained are really footprint trackways. Perhaps from the stratigraphic chart. The they were not made by tetrapods. only possibility would be for the Could there be any other explanation rocks to be assigned to a different for the depressions on the surface? stratigraphic stage. For that to happen, Such an approach would spoil the paleontologists would need to re- fun and the novelty. But the beautiful examine the fossil evidence used in evolutionary stories of fish to land the original classification, perhaps by animal, which have been so vigorously searching for other fossils in the area promoted for so long, can be retained or by examining the fossils on which intact. If the evidence consisted of an the original assignment was made. It isolated footprint it would certainly be is not unusual for a rock classification open to much question but these are a to be changed as a result of examining series of related footprints connected different fossil evidence. into a trackway and represent very The assignment would need to strong evidence that they are indeed move the rocks at least three stages made by four-legged animals. But younger, to the Famennian stage, which the thought of questioning the tracks <www.mynewsdesk.com/se/pressroom/uu/image/view/pm_ahlberg2-31243> Piotr Szrek, Uppsala University, would be quite a large move. The type is likely to be one option followed Figure 2. Limestone slab from Poland with section that defines the Eifelian stage in the paleontological community. fossil footprints. is reasonably close geographically, 40 JOURNAL OF CREATION 24(1) 2010 Countering the Critics Figure 3. Illustration showing how animal could have made Figure 4. Laser scan of surface showing detail of individual print trackways (from ref.