Fish or beast?

Recent weeks have seen evolutionary scientists hopping up and down like excited school children. In early April you may well have seen television reports touting recent discoveries in Canada of a “missing link” between finny fish and limbed animals. The hubbub was sparked by the publication of the article, “The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb” in the April 6th edition of Nature. (Tetrapods are creatures with four limbs, and include all today's mammals, reptiles, amphibians and birds.) Tiktaalik was a fish, make no bones about it (it had scales and fins). But it bore some interesting animal-like features, notably a neck and ribs. Above all, its pectoral fins — the “equivalent” of the front legs of beasts, the arms of humans and the wings of birds — are “morphologically and functionally transitional between a fin and a limb” (Nature article). Here at last we have proof that we evolved from ancient fish known as elpistostegids, of which Tiktaalik is a member.

Only a couple of weeks later a well-known Australian science program, “Catalyst”, joyfully reported the results of studies carried out by Jean Joss, encouraged by the American Museum of Natural History, on the Queensland Lungfish. The narrator declared,

This incredible fish can breathe air with a lung and tell us fantastic stories about our own ancestry. A recent Australian discovery reveals that this mysterious creature is a crucial link in the evolutionary chain that saw fish crawl out of the water to become land dwelling, back boned animals, like you and I (Lungfish).

Later in the program, Professor Joss said,

Well what we found is that the gene which is associated with the formation of digits on a hand or a foot that is fingers or toes, that same gene is associated with the formation of the radials in this lungfish fin.

We mere mortals may well find ourselves overwhelmed by such confident assertions that scientists are answering the questions related to one of evolution theory's major problems — how limbs evolved from fins and fish turned into amphibians and so on

up the line. Few stop to consider that these two reports actually confuse the issue terribly, not to mention how they illustrate the threadbare nature of standard theories; which one are we to believe? Are we to believe that tetrapods evolved from elpistostegids, as Tiktaalik suggests, or that they evolved from lungfish? You see, these creatures are placed on different branches of the alleged evolutionary “tree” (“cladogram”, in technical parlance). (See the illustration below, noting that Tiktaalik fits on the same spot on the diagram as Panderichthys.) Believe it or not, though logic tells us that air-breathing lungfish must surely be on the line towards air-breathing tetrapods, scientists had some time ago erased lungfish from the evolutionary chain. Colbert says bluntly,

… the total evidence points quite clearly to the fact that these vertebrates are not and never have been on the direct line of evolution leading from fishes to the first land-living vertebrates (Colbert's Evolution of the Vertebrates, p. 77).

Yet the new “evidence” from genetics says otherwise. But how can we believe this new evidence when it seems to be contradicted by the apparently transitional characteristics of fin-to-limb displayed by Tiktaalik? For those who plump for Tiktaalik as the more likely ancestor of you and me — in spite of the fact that elpistostegids like Tiktaalik didn't have lungs — another embarrassing fact should make them think again. Tetrapods already existed at the same time as Tiktaalik, as noted in the Chicago University home page: “And it has ribs exactly like those of its contemporary tetrapods which were used to support the body and aid in breathing”. Their remains have not been found in strata older than those containing tetrapods. The authors of the Nature article recognize this point, and put Tiktaalik in a “sister group of tetrapods” rather than in a direct line of evolution. Popular reports ignore such vital facts.

Naturally, whenever new extinct animals are discovered, they are going to have features that are like some other creatures and unlike some other creatures. The eye of evolutionary faith sees every feature of every creature as transitional between it and something similar to it. Tiktaalik was specifically designed, intelligently, for living in very shallow water where a “half-limb” would be just the ticket for survival.