Fish-o-pod ‘Missing Link’ Discovered: Media Goes Nuts

first_imgEvolutionists could hardly feel more relieved.  Just when anti-evolutionary sentiment is on the rise, a new fossil has been announced that gives pro-evolutionists a missing link to run up the fishpole, and boy, did the media salute.  Neil Shubin (U of Chicago) and two partners found a “tetrapod-like fish” fossil on a Canadian island.  It helps fill one of the most puzzling transitions in the fossil record, they said: the evolution from a fish to a land animal.    To hear the media celebration over this underwater Archaeopteryx, it would sound like the war is over and evolution wins.  Creationists have been complaining about gaps in the fossil record, and here is a perfect case of a transitional form.  One scientist smirked, “It’s good of the Intelligent Designer to continue to provide missing links, don’t you think?”  Here are just a few of the claims being made in the press about Tiktaalik roseae, the newest icon of evolution (emphasis added in all quotes):EurekAlert: a “key marker in the evolutionary transition of fish to limbed animals.”News@Nature: this is “the fish that crawled out of water” – a true ‘missing link’ that “it helps to fill in a gap in our understanding of how fish developed legs for land mobility, before eventually evolving into modern animals including mankind.”BBC News:  “Fossil animals found in Arctic Canada provide a snapshot of fish evolving into land animals… giving researchers a fascinating insight into this key stage in the evolution of life on Earth.”…. Could “could prove to be as much of an ‘evolutionary icon’ as – an animal believed to mark the transition from reptiles to birds.”Scientific American:  “Newfound Fossil Is Transitional between Fish and Landlubbers.”New Scientist:  “IT WAS one of the most important events of the last 400 million years: the moment our fishy ancestors began hauling themselves onto dry land.  Now a fossil from the very beginning of that crucial transition has been found in the remote Arctic.”  Neil Shubin calls it a “a ‘fishopod’: part fish, part tetrapod.”AP, via MSNBC:  “Scientists have caught a fossil fish in the act of adapting toward a life on land, a discovery that sheds new light on one of the greatest transformations in the history of animals.  Researchers have long known that fish evolved into the first creatures on land with four legs and backbones more than 365 million years ago, but they’ve had precious little fossil evidence to document how it happened…. ‘It sort of blurs the distinction between fish and land-living animals,’ said one of its discoverers, paleontologist Neil Shubin of the University of Chicago.”National Geographic:  “It’s our closest fish cousin, scientists say.  Millions of years ago it apparently hoisted its croc-like head out of the water—and the rest is history.”New York Times:  “Other scientists said that in addition to confirming elements of a major transition in evolution, the fossils were a powerful rebuttal to religious creationists, who have long argued that the absence of such transitional creatures are a serious weakness in Darwin’s theory.”LiveScience:  “Fishy Land Beast Bridges Evolutionary Gap.”L.A. Times:  “One Small Step for Fish… ” (fill in the next line; at least the LA Times wins cleverest title).  “These exciting discoveries are providing fossil Rosetta Stones for a deeper understanding of this evolutionary milestone – fish to land-roving tetrapods,” said H. Richard Lane (NSF).One gets the distinct impression they think this is an important fossil.  Now that the parade has passed by, perhaps it would be a good time to delve into the original scientific papers and see what exactly was said.  It made the cover story of Nature.  There were two papers inside by Shubin’s team, and a review article by Jennifer Clack, a leading researcher on tetrapod origins.  In journal articles, where scientists talk to themselves, they are expected to be more formal, reserved and cautious about interpretations.  Let’s see.    The research was first submitted to Nature in October, but released today.  The fact that the mainstream media were all prepared with instant artwork, interviews and sound bites makes it likely they were clued in with plenty of time to make a splash.  Though it is clear the authors all believe this is an evolutionary transitional form, the most interesting statements from scientific papers are usually the caveats and disclaimers.  Most of all, the observational data must always take precedence over interpretations.    In the first paper by Daeschler, Shubin and Jenkins,1 they begin, “The relationship of limbed vertebrates (tetrapods) to lobe-finned fish (sarcopterygians) is well established, but the origin of major tetrapod features has remained obscure for lack of fossils that document the sequence of evolutionary changes.”  That is a strange statement for a scientific paper.  It sounds something like, We know it’s true; we just lack evidence.Here we report the discovery of a well-preserved species of fossil sarcopterygian fish from the Late Devonian of Arctic Canada that represents an intermediate between fish with fins and tetrapods with limbs, and provides unique insights into how and in what order important tetrapod characters arose.  Although the body scales, fin rays, lower jaw and palate are comparable to those in more primitive sarcopterygians, the new species also has a shortened skull roof, a modified ear region, a mobile neck, a functional wrist joint, and other features that presage tetrapod conditions.  The morphological features and geological setting of this new animal are suggestive of life in shallow-water, marginal and subaerial habitats.Sounds like the popular press so far; now, into the details.  They admit that “The evolution of tetrapods from sarcopterygian fish is one of the major transformations in the history of life and involved numerous structural and functional innovations, including new modes of locomotion, respiration and hearing.”  In other words, many substantial changes had to come together in one animal to go from breathing through gills to breathing with lungs, developing feet that could support the weight, developing digits and ankles and toes and learning how to use them, and much more:During the origin of tetrapods in the Late Devonian (385-359 million years ago), the proportions of the skull were remodelled [sic; implies intelligent design], the series of bones connecting the head and shoulder was lost, and the region that was to become the middle ear [sic; implies progress] was modified.  At the same time, robust limbs with digits evolved, the shoulder girdle and pelvis were altered, the ribs expanded, and bony connections between vertebrae developed.Few of these innovations are seen in the closest relatives of tetrapods, they say.  They talk about Panderichthys, Acanthostega and Ichthyostega, which have been discussed earlier in these pages (see 04/05/2004 and 08/09/2003, “Evolution of the Darwin Fish.”).  Surprisingly, however, they dismiss them as fragmentary and of doubtful utility.  This includes the earlier leading candidate for missing link:Panderichthys possesses relatively few tetrapod synapomorphies [convergent features], 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.The discrediting of previous specimens was the build-up to the new fossil, which, they boasted, “significantly enhances our knowledge of the fish�tetrapod transition.”  (This boast should be taken with a grain of salt, considering that similar claims were made about Panderichthys.)  Proceeding on, they place Tiktaalik somewhere between Panderichthys and the first hypothetical tetrapods.    The paper next provides the obligatory data for a new species: location found, taxonomy, nomenclature, description of the fossil, photos, drawings, etc.  The head was remarkably well preserved, and three specimens were found.  Naming and classifying an extinct species, however, provides the discoverers some leeway in placing it into the presumed evolutionary framework.    A technical description of parts ensues.  Compared to the earlier known fossils, Tiktaalik has a larger this and a smaller that, etc.  For all its impressive jargon, the technical description does not in itself establish the case that the creature was evolving into a tetrapod.  Data provide the hard evidence, but interpretations are subjective.  Side-by-side skull comparisons do not look that informative, especially when there are no soft parts and no videos of how the creature actually lived.  It must be remembered, for instance, that Coelacanth was long considered a transitional form because of its bony fins, but when discovered alive, the fish did not use them for walking or raising itself up in any way.    Without soft parts such as gills and organs, and without living examples, interpretation of anatomy from bony parts alone is at best an exercise in educated guesswork; consider, as a hypothetical example, the surprise of a paleontologist finding a live skunk after only knowing the animal from its skeleton.  Subjectivity becomes much more an issue when constructing evolutionary trees, because evolutionary paleontologists presuppose that the fish-to-tetrapod transition occurred; also, and it cannot be discounted that a specialist in the field, who has taken great pains to find a specimen, and whose career is riding on the outcome, would like to become known as the discoverer of “the” missing link.  When these authors turn to the phylogenetic position of Tiktaalik, what features led them to conclude these specimens are transitional?A phylogenetic analysis of sarcopterygian fishes and early tetrapods (Fig. 7) supports the hypothesis that Tiktaalik is the sister group of tetrapods or shares this position with Elpistostege.  Tiktaalik retains primitive tetrapodomorph features such as dorsal scale cover, paired fins with lepidotrichia, a generalized [sic] lower jaw, and separated entopterygoids in the palate, but also possesses a number of derived [sic] features of the skull, pectoral girdle and fin, and ribs that are shared with stem tetrapods such as Acanthostega and Ichthyostega.  Tiktaalik is similar to these forms in the possession of a wide spiracular tract and the loss of the opercular, subopercular and extrascapulars.  The pectoral girdle is derived [sic] in the degree to which the scapulocoracoid is expanded dorsally and ventrally, and the extent to which the glenoid fossa is oriented laterally.  The pectoral fin is apomorphic [i.e., derived, more developed] in the elaboration of the distal endoskeleton, the mobility of segmented regions of the fin, and the reduction of lepidotrichia distally.In summary, they think that Panderichthys, Elpistostege and Tiktaalik represent a “paraphyletic [partially evolved] assemblage of elpistostegalian fish along the tetrapod stem that lack the anterior dorsal fins and possess broad, dorsoventrally compressed skulls with dorsally placed eyes, paired frontal bones, marginal nares, and a subterminal mouth.”  However, “Some tetrapod-like features evolved independently in other sarcopterygian groups,” while two other fossils seem to have features shared with basal tetrapods by convergent evolution (homoplasy).  It seems like the fossil record shows a smorgasboard of mixed features among ancient fish rather than a clear line leading up to land.  (Consider this in the context that the vast majority of species on earth are extinct; one could make up any number of possible lineages; see quote by Henry Gee in article on ID the Future.)    That’s basically all that was claimed in the primary announcement.  Their second paper2 discussed the pectoral fin of Tiktaalik, which they claim is “morphologically and functionally transitional between a fin and a limb.”  They think the front fins allowed the creature to hoist itself up and possibly drag its tail behind.  The “wrist,” however, lacks five digits (fingers), and represents a “mosaic” of features found in more “basal” taxa.  Though additional “wrist” bones extended distally are new features of this fossil, they inferred the presence of the missing digits on their diagram by dotted lines.  Lacking living representatives, they also are unable to tell for certain what the fin bones actually were used for.    While acknowledging that the transition from water to land would require “major shifts in developmental genetics, skeletal structure, and biomechanics,” they argued that the most telling aspect of the fin is the angle of the putative “wrist” bones.  However, there is no evidence any true digits for locomotion later evolved from the fin bones of this particular animal.  Since they might have, though, reporters were probably more tuned to the confident conclusion:The pectoral skeleton of Tiktaalik is transitional between fish fin and tetrapod limb.  Comparison of the fin with those of related fish reveals that the manus [hand] is not a de novo novelty of tetrapods; rather, it was assembled in fishes over evolutionary time to meet the diverse challenges of life in the margins of Devonian aquatic ecosystems.OK, now what do other experts think?  In the same issue,3 Erik Ahlberg and Jennifer Clack gave their analysis.  It is unknown whether Clack, who has been in the forefront of research into tetrapod evolution, was scooped by this discovery, or whether any personal feelings or rivalries were involved.  She did, however, with Ahlberg, put a few brakes on the interpretations, though acknowledging the significance of the find.  First, a little sermonette on missing links:The concept of “missing links” has a powerful grasp on the imagination: the rare transitional fossils that apparently capture the origins of major groups of organisms are uniquely evocative.  But the concept has become freighted with unfounded notions of evolutionary ‘progress’ and with a mistaken emphasis on the single intermediate fossil as the key to understanding evolutionary transitions.  Much of the importance of transitional fossils actually lies in how they resemble and differ from their nearest neighbours in the phylogenetic tree, and in the picture of change that emerges from this pattern.    We raise these points because on pages 757 and 764 of this issue are reports of just such an intermediate: Tiktaalik roseae, a link between fishes and land vertebrates that might in time become as much of an evolutionary icon as the proto-bird [sic] Archaeopteryx.Though this fossil goes “a long way” to filling in the gap, it does not go quite all the way, they say.  Its closest match is Elpistostege, a fragmentary fossil thought to be closer to tetrapods than Panderichthys.  They admit, “the authors demonstrate convincingly that Elpistostege and Tiktaalik fall between Panderichthys and the earliest tetrapods on the phylogenetic tree.  End of story?  Not quite.  Though impressed, they raise some issues.  Of the fin bones, they squelched most of the enthusiasm, emphasizing instead the long road ahead:Although these small distal bones bear some resemblance to tetrapod digits in terms of their function and range of movement, they are still very much components of a fin.  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.  The implication is that function changed in advance of morphology.Though each fossil seems to represent a mosaic of characteristics rather than a straight line of evolution, Clack and Ahlberg were ready to agree that the creature was a piece of the mosaic.  It was “evidently an actual step on the way from water to land,” and that “it seems, our remote ancestors [sic] were large, flattish, predatory fishes, with crocodile-like heads and strong limb-like pectoral fins that enabled them to haul themselves out of the water.”  Nevertheless, this is just one specimen, and many more will be needed to confirm the transition.  Any one creature must be seen in that context.  Their concluding paragraph effectively deflates most of the optimism about this fossil.  They claim that the most important transitional forms are found, where? – in the future:Of course, there are still major gaps in the fossil record.  In particular we have almost no information about the step between Tiktaalik and the earliest tetrapods, when the anatomy underwent the most drastic changes, or about what happened in the following Early Carboniferous period, after the end of the Devonian, when tetrapods became fully terrestrial.  But there are still large areas of unexplored Late Devonian and Early Carboniferous deposits in the world – the discovery of Tiktaalik gives hope of equally ground-breaking finds to come.Update 04/22/2006:  Joseph Farah reads Between the Lines on the missing-link claim about Tiktaalik (see 04/06/2006) on World Net Daily.  Columnist Ted Byfield also mentioned the fish-o-pod in his WND editorial, “Rebutting Darwinists.”  Frank Sherwin has a response on ICR.1Daeschler et al., “A Devonian tetrapod-like fish and the evolution of the tetrapod body plan,” Nature 440, 757-763 (6 April 2006) | doi:10.1038/nature04639; Received 11 October 2005; ; Accepted 8 February 2006.2Shubin et al., “The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb,” Nature 440, 764-771 (6 April 2006) | doi:10.1038/nature04637; Received 11 October 2005; ; Accepted 8 February 2006.3Per Erik Ahlberg and Jennifer A. Clack, “Palaeontology: A firm step from water to land,” Nature 440, 747-749 (6 April 2006) | doi:10.1038/440747a.OK, Shubin, you caught a fish and got your picture in the paper.  Now that you are feeling your oats, take on the Cambrian explosion.    You didn’t get this much detail from the major news media.  You didn’t hear the discoverers hedge their bets and admit that this fossil is just a tiny piece of a huge puzzle that is mostly not understood.  You didn’t hear the AP (Associated Preach) tell the truth that the fossil record is characterized by large and systematic gaps between groups, with only rare, isolated and questionable transitional forms.  No, you got hype and bluster and far-fetched exaggeration, where the actual bones were incidental to the true goal of making Charlie not look as dead as he is.  Meanwhile, an explanation of the origin of all the genetic information required for such a transition was completely glossed over; and, of course, not a single credible non-Darwinian paleontologist got a word in edgewise over the din of the mainstream media’s Charlie pride parade.  If you got mad last time (04/05/2004) it’s time to get mad again – for the same reasons. A reader writes:  “Dear Staff… The April 6, 2006 article on the ‘Fish-O-Pod’ found in Canada is great news… Now we know where all the Walking Catfish in the lakes in Orlando, Florida came from… They actually walk up on the interstate and get eliminated by cars!  FISH-O-POD is nothing new, we have been squashing them for years!”  Another commented on the AP coverage, “I got seasick from all the handwaving.”  To this we add, scientists are not assuming that mudskippers are transitional forms to salamanders, are they?  Or grunion to snakes, or rikshas to sedans?  Let’s play their game and daydream about beavers evolving into seals, and flying squirrels evolving into bats.  Connecting dots is child’s play.    See also a preliminary response from the Discovery Institute, followed by another by Casey Luskin on Evolution News; also, a preliminary analysis by Dr. David Menton on Answers in Genesis: “Gone fishin’ for a missing link?”  An article by Jonathan Witt on ID the Future has information on the comparison with Archaeopteryx, and contains an apropos quotation made years ago by Henry Gee, editor of Nature, on the feasibility of reconstructing phylogenetic trees from fossils.  The best part: “To take a line of fossils and claim that they represent a lineage is not a scientific hypothesis that can be tested, but an assertion that carries the same validity as a bedtime story — amusing, perhaps even instructive, but not scientific.”  And that’s from the senior editor of the same journal where this announcement appeared today.Parting thought:  In a private conversation about evolution recently, a friend responded: “I don’t have any doubts about evolution; there have been too many people working on it for too long for it to not to be well established.”  (See Bandwagon, Authority and Glittering Generalities in the Baloney Detector.)  Do you appreciate the value of delving into the details?Tip:  See this story in Spanish on: SEDIN.(Visited 44 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img