Tetrapods from Fish?
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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 26 BOOK REVIEWS || JOURNAL OF CREATION 28(1) 2014 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. 27 JOURNAL OF CREATION 28(1) 2014 || BOOK REVIEWS 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.