JOURNAL OF CREATION 28(1) 2014 || BOOK REVIEWS
Tetrapods from Fish?
Although Clack does not describe Gaining Ground: The Origin and it in this manner, she points out Evolution of Tetrapods, 2nd edn that Tiktaalik had a number of Jennifer A. Clack specializations, including a large Indiana University Press, Bloomington and number of vertebrae, which was Indianapolis, IN, 2012 atypical of either fish or tetrapods (p. 82). It thus appears that Tiktaalik was an ‘oddball’, and therefore a rather John Woodmorappe poor candidate for a transitional form between fish and tetrapods. What could Tiktaalik actually do? his work is somewhat technical It turns out that the incipient tetra- in nature, and is packed with T pod-like properties of Tiktaalik fins anatomical details. It surveys not are a matter of interpretation, not fact only the presumed evolutionary (pp. 214, 441). Clack notes: origin of tetrapods, but also their “It appears that the ‘wrist’ was condition than Tiktaalik (p. 88), had inferred adaptive radiations in the able to rotate and flex in a way a more tetrapod-like skeleton than Carboniferous. Because this subject similar to that of a tetrapod, and Tiktaalik (p. 214). is rapidly undergoing study, I include that suggests a supportive role, That should settle it. Tiktaalik is a more recent publication.1 raising the forequarters out of water. hardly an earth-shaking milestone This review considers the highly Additionally, the long imbricating in the presumed evolution of fish touted transitional Tiktaalik, and ribs presumably must have borne to tetrapods. By no stretch of the other ‘fishapods’. It then entertains muscles to keep the body rigid as imagination is it a proven legged evolutionary arguments based on such it did so. Whether it could actually walking fish! things as stratomorphic intermediates leave the water using its fins as Returning to the malicious lamp- and the alleged explanatory power of ‘legs’ is not certain. Crucially, ooning of creationists in the wake of evolutionary interpretations. the pelvic fin and girdle remain the discovery of Tiktaalik, perhaps To avoid confusion, I use the term unknown” (p. 84). a little nemesis is in order for the ‘ambling’ to refer to unspecified forms Other parts of Tiktaalik’s skeletal intellectual hubris of the evolutionists of locomotion across land, and restrict anatomy are little more definitive. (see figure 1). Tiktaalik thus joins the the term ‘walking’ to refer specifically Clack comments, Piltdown Man, Archeopteryx, etc. as to locomotion across land by the use “It might be supposed that one of the greatly-overhyped ‘missing links’ that are somewhere between questionable of jointed, weight-bearing limbs. This parts of the skeleton to have been and bogus. distinction is important, as further most affected at the fish-tetrapod noted, though it is my term for purpose transition would be the vertebral column … . The information of reference, and not actual scientific More advanced ‘fishapods’— now coming from creatures like terminology. dubious ‘legs’ for walking Tiktaalik and Ichthyostega are giving mixed messages about the As if Tiktaalik was not enough, fossils Tiktaalik—not a leg to stand on early evolution and functioning that are more derived than Tiktaalik, of the axial skeleton during the cladistically speaking, and more Pardon the pun in the title. When transition, and it is no longer so recent stratigraphically (see pp. 60, 88), Tiktaalik was first discovered, easy to determine what kind of additionally lack compelling evidence there was a great media hullaballoo axial morphology is primitive” of full-fledged tetrapod locomotion. about this ‘legged walking fish’, and (pp. 416–417). This includes the crucial evidence evolutionistic triumphalism about What about progress towards of limbs that have weight-bearing it waxed eloquent. A whole series the eventual tetrapod condition? (I am capabilities. Clack points out that of cartoons were drawn to lampoon using, of course, the word ‘progress’ “Unfortunately, in almost all creationists, and to do so with no small in terms of outcomes, not goals.) very early tetrapods, wrist and amount of sarcasm (see the Google Ironically, Panderithys, which is less ankle bones tend to have been Images on Tiktaalik). derived towards the eventual tetrapod poorly ossified and hence were
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Late Devonian lobe-finned fish and amphibious tetrapods. Ichthyostega Land Tiktaalik
Rivers, Swamps, Acanthostega Shallows Panderichthys
Eusthenopteron Coelacanth
Sea Millions of years ago
385 380 375 370 365 360
Figure 1. The phylogeny of tetrapods presumably evolving from fish.
poorly fossilized. The ankles of In conclusion, the gap between In terms of lower jaw morphology, Ichthyostega and Acanthostega, and ambling fish and walking tetrapods not Ichthyostega comes out as more both ankle and wrist of Tulerpeton only still exists, but also remains rather primitive than Acanthostega. The … constitute conspicuous excep- large. Clack tacitly admits as much: results are further contradictory tions to this observation. The ankles “Because of circumstances such as when more traits are considered. of Ichthyostega and Acanthostega these, the transition from the earliest Clack concludes that the phylogeny are consequently known to be and presumably non-weight-bearing of Devonian tetrapods is unstable, rather different from those of joints to those that were more fully and invokes the standby of parallel tetrapods known from the mid-Late terrestrial is still poorly understood. evolution to explain (or explain away) Carboniferous, having fewer bones Once these features are more clearly this situation (p. 184). and no obvious lines of flexibility reflected in the bony skeleton, it Nor does the fossil organism becomes possible to say more about that would have allowed the foot qualify as transitional form if it is terrestrial adaptation of limbs and intermediate in some traits, while to be placed flat on the ground for vertebrae …” (p. 443). singularly discordant in others (in weight bearing …” (pp. 442–443). other words, it is specialized). Clack, She adds, “Even in Tulerpeton, it though no creationist, recognizes the is not clear that the joints would have What an evolutionary transitional magnitude of this problem: been as flexible as those of later, more form is not “In the past, a temnospondyl such terrestrial tetrapods” (p. 443). A transitional form is not merely a as Eryops would have been featured She adds that mosaic consisting of an assortment of in the role of primitive tetrapod, “Acanthostega’s wrist was quite features normally typical of different and Ichthyostega would have been unlike the wrist of subsequent forms of life. Thus, in the context of seen as an intermediate between tetrapods. Because the radius and this review, a fossil that exhibits a Eusthenopteron and Eryops. ulna were such different lengths, mosaic of reputed piscine and reputed Recent analyses, however, have the ends could not have formed tetrapod features (even if validly suggested that Ichthyostega has an effective bearing surface on interpreted) does not, by itself, qualify some highly specialized features which the animal’s weight could as a transitional form. that may make it unsuitable as be balanced … . Similarly, the One obvious example of mosaicism, a representative Devonian ankle joint was also unsuitable as a and inconsistent mosaicism at that, tetrapod; it is now also clear that weight-bearing joint, being rather is found in Acanthostega and the Eryops is a higly specialized and inflexible …” (p. 173). more derived Ichthyostega (figure 2). unrepresentative temnospondyl.
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Although Eusthenopteron is not has a structure that is 90% fin and of fossils and their relative positions as close a relative of tetrapods 10% leg, succeeded in turn by a form in fish-to-tetrapod phylogeny. This, as used to be considered, it still that has a structure that is 80% fin at best, is a half-truth. Friedman and provides good information about and 20% leg … through a fossil that is Brazeau comment: basal tetrapodomorph structure” finally 100% leg. Much the same fine “Before the Polish trackways high- (p. 187). progression should be exhibited by lighted the missing pre-Givetian other traits, such as a fossil whose skull record of ‘elpistostegalians’ and is 100% fish, through fine successive digited tetrapods, there were What, then, is an evolutionary intermediates, to one whose skull is already indications of outstanding transitional form? 100% tetrapod. stratigraphic gaps in the Devonian Far from backpedalling on Using cladistic language, the tetrapod record. Most major piscine ‘transitional forms’ in the face of foregoing definition of transitional branches in tetrapod phylogeny successive discoveries of fossils, as forms can be expressed as follows: a (rhizodonts, osteolepidids sensu often accused, scientific creationists series of ever-more-primitive sister stricto, megalichthyids, canowind- rids and tristichopterids) make their have always been consistently and groups, each of which is discontinuity- debut in the Eifelian-Givetian. perfectly clear about what they do free, towards both its stemward and the Unlike more crownward stretches mean by genuine transitional forms. crownward forms, none of which has of the stem, where clade rank and For example, back in 1974, Duane any specializations. FAD [First Appearance Datum] T. Gish wrote a booklet titled “Have The facts are clear. Nothing that are tightly correlated, these deep You Been Brainwashed?” In it, he evolutionists have found in the 40 years branches show no clear relation- specified what genuine evolutionary since the immortal Duane T. Gish ship between stratigraphy and transitions should look like, if they defined transitional forms comes close phylogeny.” 2 existed. Consider the fish evolving to fulfilling this challenge! One must ask, in addition, if into a tetrapod. Immediate ancestor- the agreements that do exist are descendant relationships, which Stratomorphic intermediates? at least partly the result of subtle are next to impossible to infer, are preconceptions. Could evolutionists not required. However, one should Some evolutionists, including be subtly influenced in their choice of see a series of very gradational those who may concede the failure of traits for use in their cladograms by the intermediates on all the traits that morphological transitions, have now order of stratigraphic appearance of differentiate the fish from the tetrapod. claimed that, given the known fossil the fossils that they are working with? The series should show a fossil with record, there is a close correspondence Some evolutionists have made 100% fin, succeeded by a fossil that between the stratigraphic appearance much of the fact that chains of inferred evolutionary changes occur at highly constrained stratigraphic intervals in the Phanerozoic geologic column. “Just where we need them, that is where they are”, say the evolutionists. Let us examine this argument in light of the fish–tetrapod transition. Friedman and Brazeau have used quantitive evolutionary methods to factor the unexpected early appearance of the Zachelmie trackways in Poland in terms of the first appearance of the tetrapods.3 Their three scenarios (good choice of word) all require considerable ghost lineages—wherein putative ‘fishapods’ existed but left no fossil record. Depending upon such input information as assumed probability of fossil preservation, the Image: Tim Newcombe Image: 95% confidence intervals span not only Figure 2. The fate of Tiktaalik. most of the Devonian, but, according
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to one set of assumptions, even down other things, assumes that evolutionary As it turns out, not only did this to the mid-Silurian!4 What’s more, explanations are highly constrained evolution prediction fail, but also, as if this does not factor in the additional and testable. This, in turn, implies that to spite the evolutionist, the evidence uncertainties of ‘tetrapodness’ well evolutionists can make very specific shows the exact opposite. Clack into the Carboniferous. (The earliest predictions (actually, deductions), and comments: recognized terrestrial tetrapod, then locate highly specific evidences “Before it [the modern coelacanth] Casineria (p. 443), does not appear that uniquely correspond to these was studied in its natural environ- until the early-mid Visean stage of predictions. All this is supposed to ment, many people predicted that the Early Carboniferous (p. 260).) endow evolutionary theory with great its fin structure would mean that it Thus, the inferred fish-to-tetrapod explanatory power. used fins for walking on the bottom evolutionary makeover smears over as Clack considers evolutionary of the sea or among the coral reefs many as three geologic periods, and, predictions, but prefers the word where it lived. However, film of in any case, is hardly ‘constrained’ scenario to prediction (p. 135). In the fish in action shows that this is stratigraphically at all. addition, she frankly admits that, never the case; it uses its paired fins Is it not significant, however, that for one reason or another, many for slow paddling … . The lungfish the so-called fishapods have tetrapod evolutionary scenarios are untestable Protopterus has been observed to features at all, implying at least a (pp. 173, 242). prop itself up on the substrate using crude evolutionary and stratigraphic Consider the inferred evolutionary thin whiplike appendages that are progression towards the eventual processes that transformed fish fins most unlimblike” (p. 136). tetrapod condition? Not necessarily. into tetrapod legs. Since evolution The boniness, or lack thereof, Clack quips: lacks foresight, and always modifies in modern fish fins, also is the very “Apart from possession of limbs structures that existed previously, opposite of evolutionary predictions. with digits, a number of the what could be more intuitively obvious Clack points out that supposed tetrapod-like characters than the land-ambling fish subjected “The first thing to notice is that found in Acanthostega that are to natural selection that favours these two groups are almost often linked with terrestriality can increasingly distant, increasingly mutually exclusive—that is, those actually be found among modern rapid, and increasingly efficient land- with digitlike fin rays by and large fishes that have no reputation as based locomotion, culminating in the are not those that venture unto land dwellers” (p. 173). tetrapod leg? What could be more land, and conversely, those that do This matter can be extended into reasonable than the emergence of a venture onto land do not necessarily the broader context of the entire fossil stiff, bony fin? This would naturally do so by means of digitlike or record, and to the present. There are favour improved weight bearing limblike fins” (p. 136). various fishes that can amble across and then improved ambling on land, Clack then discusses factors that land (as from one pond to another), eventuating in a full-functioning may have led to the origin of tetrapods, or which have bony fins of various tetrapod leg. and concludes: types, yet no one suggests that they are ‘stratomorphic intermediates’ of some sort. As an example, consider the modern Sargassum frog fish (for drawing, see p. 137; for a frog fish in general, see figure 3). Its pectoral and pelvic fins, according to Clack, exist as jointed, digitlike fingers and toes.
Evolution’s ‘explanatory power’— origin of legs Evolutionists usually claim that Special Creation is not scientific, not only because of supernaturalism, but also because ‘The Creator can do anything’, and so the creation explanation is unconstrained and untestable. This argument, among Figure 3. An example of a frog fish—a modern fish that can amble on its bony fins.
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“Nonetheless, it is difficult to discoveries show that the earliest Testability of evolution? tease apart all the influences that tetrapods were not pentadactyl after What, then, do evolutionists mean were at work in the Devonian all, and the evolution of joints and when they say that evolution is testable? to produce the appearance of digits did not proceed in the order of Obviously, they are not talking about tetrapods. Ideas are numerous, but fashion that early theoretical studies experimental verification, since we are evidence is equivocal. Most ideas assumed …” (p. 136). dealing with the unobservable past. can be countered by objections or Furthermore, current interpreta- Nor are they talking about the overall alternative suggestions, or they tions of what aspects of ‘tetrapodness’ evolution explanation, of living things, are difficult or impossible to test. evolved first (including that based itself being testable. They are talking Without a much more complete on clues from embryology and about specific evolutionary scenarios fossil record, they must remain comparative anatomy) could admit- being testable. The test involves speculative” (pp. 140–141). tedly be completely overturned with whether or not some scenario clashes So much for the wonderful the discovery of new and earlier with incontrovertible evidence, as that explanatory power of evolutionary ‘fishapod’ fossils (p. 257). Obviously, from fossils. Obviously, evolution is theory! if extra-paleontological evidence was not being read out of the evidence. conclusive, this could not be so. Evolution is being read into the ‘Tests’ of evolution—comparative Let us examine this in a bit more evidence. No matter what turns up, anatomy, Hox genes, detail. Fossils can refute deductions some kind of post hoc evolutionary and embryology of presumed evolution based on reasoning (or storytelling) is imposed upon the data. There has been, in recent years, a embryological development. For revival of a form of the old embryo- instance, a forbidden morphology logical recapitulation idea among implied by embryological evidence Conclusions (the shortest digit must be at the evolutionists. Clack assesses in- The discontinuity between fish end of the five, not the middle), has formation from embryology as follows: and land-walking tetrapods remains. been refuted by fossil evidence “Part of the problem of posing such The ‘walking fish’ Tiktaalik has (p. 252). It is obvious that evidence theoretical ideas is that they are busted as fast as it had boomed. Other based on the study of such a limited from embryological development is ‘fishapods’ are just as unconvincing. sample of experimental animals. in no sense diagnostic. Instead, it is The inferred evolutionary progression Zebra fish, mice, chickens, and the ‘juggled’ with other evidences. from fish to tetrapods is inconsistent frog Xenopus, the most commonly Evidence from Hox genes, at from morphology to morphology. In studied laboratory animals in least at this stage, is conjectural. addition, it smears over a considerable developmental biology, all belong to For instance, Clack (p. 253) points stretch of inferred geologic time. species that are highly specialized out that there is no explanation for Evolutionary arguments about members of their vertebrate groups. why we have five fingers and five stratomorphic intermediates and the This means that they may not always toes. Is the constraint developmental, predictive powers of evolutionary be representative of tetrapods as a functional, or some combination of explanations are of dubious validity. whole, and they certainly cannot the two? Early vertebrates sometimes account for many of the extreme had more than five, as Clack had specialization that some tetrapods References noted previously (above). If early show” (pp. 252–253). evolutionary ‘experimentation’ 1. Friedman, M. and Brazeau, M.D., Sequences, Obviously, information from stratigraphy and scenarios: what can we say allowed for non-pentadactyl limbs, about the fossil record of the earliest tetrapods? embryology is not self-evident or Proceedings of the Royal Society (Biological then why did it not happen thereafter? empirical. It is not only a matter of Sciences) 278:432–439, 2011. interpretation, but also a matter of post Clack speculates that Hox genes may 2. Friedman and Brazeau, ref. 1, p. 437. hoc evolutionary reasoning. be at least partly responsible for the 3. Friedman and Brazeau, ref. 1, p. 433. Clearly, data from embryology and ‘canalization’ of development into 4. Friedman and Brazeau, ref. 1, p. 435. Hox genes, like that from comparative pentadactyl limbs only. Regardless, anatomy and paleontology, is a matter it refutes the evolutionary icon of the of integration and interpretation, as is pentadactyl limb as the classic example obvious from the following statement of homology, supposedly proving by Clack: common ancestry, since the proposed “The second major objection to the candidates for common ancestor were fin-to-limb scenarios is that recent not pentadactyl.
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