A Response to Matt

My last post, Radical Revision, elicited a thoughtful response from Matt. Here is his email to me, and my response.

Matt: Hi, I have a few questions for you:

Could I ask you to clarify your point in why you included the anecdote about tetrapod anatomy in your article? Is it because you claim it to be a finding that “upsets the standard teaching”?

If so, could you please clarify what you think the “standard teaching” is and how you think that this finding “upsets it”? Could you also clarify the big picture for me? What is the importance of Ichthyostega? Why do researchers care about it’s anatomy?

Also, you ended your article, “As we move further away from repeatable, observable and limited phenomena, the claim of scientific knowledge becomes weaker and weaker.” I agree with the pshat of this statement, but I feel like there is implied subtext in your article. Are you referring to anything in particular?

My Response:

As I wrote in the post, the tetrapods (or their close relatives) are the creatures that are believed – by evolutionary biologists – to have made the transition from life in the sea to terrestrial life. This is one of the most crucial episodes in the history of life, as portrayed by evolutionary biologists. All terrestrial life – from bees to beavers to Benny – is supposedly descended from the tetrapods. So they are an exceptionally important element in the history of life. The fact that the textbooks have been wrong about the basic anatomy of tetrapods for the past 150 years is therefore extremely significant.

If you follow the link to the BBC report that I provided in the post, you will see a reconstruction of one of the tetrapods. Many members of the public, when confronted with such reconstructions, entertain exaggerated notions about the reliability and accuracy of this and similar reconstructions. In fact, these reconstructions are based on paltry information contained in fragments of fossilised bones. The report which I discussed in the post underscores this point. For 150 years, the picture which researchers had of the anatomy of these creatures was, literally, back-to-front. How much confidence, then, should one have in the claim that these creatures are sufficiently well understood to convince us that they or their relatives were capable of moving from the sea to land?

Moreover, this is not the first time in history that this sort of thing has happened. In a previous iteration, it was the rhipidistians, and their relative the coelacanth, that were touted as the first fish to make it on land. Based on numerous fossils of the coelacanth, biologists were convinced that this fish had various adaptations that made it possible for it to achieve locomotion on land. In the late 1930s, a living coelacanth was discovered off the coast of South Africa (since then, many coelacanths have been caught and studied). It was now possible to examine the soft tissues of the fish, and to compare what had been predicted from the fossils to the reality. As Peter Forey wrote,

“… [Before the modern discovery of the coelacanth] many fossil coelacanths were described and, on the basis of osteological features, their systematic position as near relatives of the extinct rhipidistians… had become part of “evolutionary fact”, perpetuated today in textbooks. Great things were therefore expected from the study of the soft anatomy and physiology of [the coelacanth]…” [Peter Forey (1980), Latimeria: A Paradoxical Fish, Proceedings of the Royal Society of London, B208: 369-84]

The result of studying living coelacanths: coelacanths had no pre-adaptation at all to life on land. They were fish, pure and simple. You could make gefilte fish with coelacanth. As Barbara Stahl, an expert on this subject, put it,

“… The modern coelacanth shows no evidence of having internal organs pre-adapted for use in a terrestrial environment… The heart is characteristically fish-like… and the gut… is of a type common to all fishes…” [B. J. Stahl (1974) Vertebrate History: Problems in Evolution, McGraw-Hill page 146].

All of this should give informed consumers of science pause when confronted by claims about life emerging from the sea and adapting to land. Life in the sea and life on land are fundamentally different propositions, and tens of thousands of adaptations would have to occur for that transition to happen. (Think of turning a submarine into a tractor, and try to count the number of changes that have to be made). Furthermore, many thousands of these adaptations would have to occur simultaneously. The evidence presented for this fantastical hypothesis turns out to hinge, to a significant extent, on some shards of bone, which have been badly misinterpreted for the past 150 years.

In summary:

1. The standard teaching that I was referring to is that the tetrapods (or close relatives) made the transition from sea to land. It is significantly weakened by the discovery that basic anatomical features of these creatures were completely misunderstood for the past 150 years.

2. Researchers care about tetrapods because they form such an important element in the evolutionary scenario. These are not mere creatures that appear, live and become extinct, like the vast majority of organisms that populate the fossil record. Without some plausible explanation as to how fish become pre-adapted to life on land, the evolutionary scenario becomes another just-so story.

3. My concluding statement was general. Informed consumers of science know how to discriminate between various scientific claims. They can assign appropriate levels of credibility to various scientific claims. As I explain at length in Genesis and Genes, we have greater confidence in scientific results that concern repeatable, observable and limited phenomena. Claims about the alleged transition of fish from life in the sea to life on earth should be treated with extreme scepticism.


One Response to “A Response to Matt”

  1. Matt Says:

    First off, thank you for the thoughtful response. I really appreciate your taking the time to answer my questions.

    “The standard teaching that I was referring to is that the tetrapods (or close relatives) made the transition from sea to land.”

    I would argue that this statement still holds true, regardless of the spinal orientation. The spinal orientation is difficult to know, because it seems that this part of the specimen is embedded in rock. But, there are many equally essential anatomical features which are clearly visible: the structure of the limbs, the shape of the skull (for which there are several specimens), the the teeth, the jaw bone. I would argue that the standard teaching, as you have articulated it, is “robust”, even if one particular part of the anatomy were uncertain…especially since there are many other transitional fossils in this series.

    “It is significantly weakened by the discovery that basic anatomical features of these creatures were completely misunderstood for the past 150 years.”

    Here is where I think you may be taking license. Phrases like “significantly weakened” and “completely misunderstood” are subjective statements. As a “consumer of science”, I prefer more precise and objective terminology. Having read the Nature article and the BBC article, I get the impression that this is a more subtle anatomical distinction than you would like it to be. The researchers who do this work are passionate and I very much appreciate their excitement in proclaiming that “textbooks will have to be rewritten”. However, I think that they are talking about *graduate level* textbooks. I don’t think that they mean to suggest that this overthrows the big picture of where that creature fits into the record.

    You claim that this finding “significantly” weakens the notion that Ichthyostega represents a transitional form from fish to amphibian. Allow me to quote the BBC article: “Prof Hutchinson said the findings provided more clues about how the early animals physically moved out of the water and on to land.” This seems to suggest the opposite of your conclusion.

    In the end, as someone who would like to think of himself as “an informed consumer of science” I musty humbly admit that, not being a paleontologist or zoologist, I don’t feel confident making any serious judgement. Is it safe to say that you too are not an expert on this subject matter?

    Might I suggest that we contact the researchers themselves and see what they say? Would you post their response?

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