Stranger Fruit


I haven’t catfish blogged in a while, so this is worthwhile. Another article in today’s Nature is of interest. In this one, the authors describe the ability of the eel catfish, Channallabes apus to forage onland. Importantly, they note that the species’ “capacity to bend its head down towards the ground while feeding seems to be an essential feature that may have enabled fish to make the transition from an aquatic to a terrestrial mode” and go on to point out that the species and others such as Ichthyostega, the recently described Tiktaalik, and terrestrially feeding Periophthalminae (terrestrially feeding mudskippers) all show “dorso-ventral flexion of the presacral vertebral column, and this may have allowed these animals to capture prey on land more effectively.” Isn’t in nice when all the evidence comes together?

The paper is Van Wassenbergh et al. (2006) “Evolution: A catfish that can strike its prey on land” Nature 440, 881 (13 April 2006) | doi:10.1038/440881a


  1. #1 grrreat_ape
    April 12, 2006

    I wasn’t certain where this comment would be most appropriately placed on this site, but I figure a land-roaming catfish thread is amenable to a wide range of topics…

    I wanted to comment on my recent interaction with the folks at the ID blog. I’m rather new to following the “evolution controversy” via weblogs, etc, and I was actually attempting to have a dialogue with the ID folks–largely for the sake of organizing my thoughts concerning evolutionary theory. Well, apparently the post I made (text below) was simply too provocative for their tastes, and they unceremoniously booted me from the site. In retrospect, I would have been a little more careful and qualified precisely why I considered “random mutation + natural selection” a post-origin-of-life subject, but all in all, I think there’s nothing here that was impolite and/or out of bounds. Is this typical of these sites? Anyhow, I thought it might be interesting to hear about other people’s experiences in trying to engage in a dialogue with these guys.

    the post (after being rebuked for not giving an explanation for the origin of life while defending Darwinian evolution):

    “I am unclear whether I should address the math/statistics applicable to biological diversity being generated by RM+NS, or, instead, those applicable to life ever having being initiated to begin with. Previously, when trying to explain why I considered it plausible that RM+NS could generate the observed levels of biological complexity, I was accused of side-stepping the “hardest part” (i.e. the formulation of ribosomes, the first replicating cells, etc) in making my case for darwinism. Personally ,I consider that response a touch unfair since RM+NS is only meaningful in the context of existing ribosomes, cells, etc. And as ds anticipated, I would argue that these “origins” questions are generally outside the darwinian evolution debate as typically framed-particularly in relation to teaching the vast body of knowledge concerning organismal and molecular evolution. Life’s Origin, is typically a small, speculative paragraph in the textbook. That’s not to say that it isn’t important, but as scientists, we typically like to dwell longer on the things we actually have some evidence for.

    Biologists-and here I use the broadest sense of the term-are by and large concerned with conveying to students in *no uncertain terms* that there is ample evidence for common descent with modification, random mutation, natural selection, and that, along with speciation processes (an entire and fascinating subdiscipline in itself (surveyed rather well in Coyne & Orr’s “Speciation” text from 2004) that these are, in all likelihood, sufficient explanation for the complexity and diversity of biological life. It is rare that scientists (those that I know, at least) speak of the origins of life with anything other than a tone of bemused speculation. Of course, there is always the inherrent working assumption that a nonteleological/nondesign (i.e. materialistic/naturalistic) explanation exists and should be sought. (This I hold to be the proper default working assumption at the very core of our natural science tradition, but that’s an entirely different (and long) argument to make.)

    Nevertheless, the philosopher in me acknowledges that we should remain open to having that naturalistic/materialistic assumption overturned by _exceptional and overwhelming_ evidence. Such evidence has not been presented thus far. In natural science courses, we entertain plausible naturalistic explanations for the origin of life, its subsequent evolution, and the observed diversity and complexity of life. This is what is proper in the spirit of our natural science tradition, and few are arguing that it has not been a fruitful approach. Darwinism and the associated naturalistic explanations for observed biodiversity are all we have that fit the bill. I have never and will never claim that they are unquestionably correct-that’s simply not the way science works-only that they are consistent with the available data and that there are no naturalistic contenders viable enough to be taught beside it as competing theories.

    So why not teach ID and other competing explanation alongside evolution and naturalistic origins? Personally, I don’t believe we should be ruthlessly dogmattic about anything, Darwinism included. That said, there remain a number of good reasons not to introduce these as “competing theories” alongside darwininan evolution and naturalistic (chemical/biochemical) origins, in our science classes. 1) I don’t think any of these theories have broken the “exceptional and overwhelming” evidence barrier that would justify our deviating from tradition and introducing teleological-based arguments in a natural science course. 2) ID brushes up so close to theological considerations-in those cases where it doesn’t invoke theological questions directly-that it runs the risk of provoking religious dialogue in a venue where it would be counterproductive. 3) nontheologically-inspired versions of ID have their own inherrent problems. These I try to elucidate below at the same time as addressing the ribosome/firstcell/origin issue.

    The following are what I consider to be the options concerning the origin and evolution of biological complexity (including ourselves). Please correct me if I missed anything as I am interested to learn if there are any other theories that are considered with any frequency.

    1. Weak panspermia, as I understand the concept, is fine with me. Teach it as a possibility in conjunction with evolution. Heck, they may already be teaching it in some places. It’s naturalistic, it’s not implausible or essentially incompatible with current evidence. But as far as origins go, it only pushes the problem further back in time. Enter “strong panspermia.” As I understand it, this argues-in line with ID folks-that the complexity of biology could not occur by a RM+NS process. The complexity of life is thought (if I understand correctly) to be an eternal component of an eternal universe or of an eternal series of finite universes. It simply always was. Somehow the bio-complexity is seeded anew in a universe despite the big bang and its associated “liquidation” of matter. Perhaps this occurs after the bang, from another universe, through a wormhole. Now I can’t say for certain that didn’t happen. But I’m not sure I could say it was an equal enough contender to include in the textbooks and classrooms alongside evolution just yet. Can you? It would make an interesting Star Trek episode, though.

    2. Yet another: God designed the universe. Problem: Your God or mine? Proposed Resolutions: heated argument, peaceful and enlightening dialogue, physical violence. I leave it to you to assign probabilities to these. In any case, this doesn’t seem to belong in a science class. I will, ofcourse, rethink my position if we begin discovering astrological bodies with large “Made by God” stamped in them. Short of that, I’d be pretty reluctant to open this can of worms in the classroom.
    It also begs the question: how can life be too complex to occur on its own when, at the same time, you posit that an omniscient/omnipotent of inconceivable complexity can exist de facto without any explanation? Our students then descend into to medieval dungeons of metaphysics.. This leaves little time for learning the amino acid structures.

    3. Another possibility: It wasn’t God who created biological complexity, but rather some superior alien being or group of such beings. Can’t say that it didn’t happen. Again, it pushes the origin of complexity back. Presumably this being (or beings) is/are intelligent and complex… who designed them? Perhaps there was an eternal chain of such creative beings stretching back… Is this the sort of discussion we want to have in Biology 101? This was even be questionable as a Star Trek episode.

    4. Another possibility: Not often considered, but somewhat fitting with the anthro-friendly nature of the physical universe… An incomprehensibly deep multiverse in which the ridiculously unlikely event of life originating and actually flourishing (and becoming somewhat intelligent) occurred… and we’re living in it a branch of it that was conducive to…well…us. Throw in some weak panspermia to boot. It’s naturalistic. It’s interesting. Note that this scenario would be virtually indistinguishable from Design b/c seemingly “irreducibly complex” bio-systems might be found …only nothing is inherrently irreducibly complex in this inconceivably large multiverse where pretty much everything happens somewhere or another. If additional evidence for the many-worlds take on quantum mechanics is found, we might be hearing more along these lines. Until then, though, we might have another good episode of star trek on our hands, but not appropriate Bio-101 material.

    5. Finally, as the evil Darwinist propaganda machine would have you believe, our own humdrum lonely universe was vast enough, contained materials and processes (nuclear and chemical) enough, to kickstart life one or more times. Be it in an RNA world, a clay world-pick your primordial soup. After said event, this deceptively simplistic blind algorithm of RM+NS generated an incredible wealth of biodiversity. Much of it was subsequently annihilated by giant rocks falling from space. From the remnants, life triumphantly emerged and new diversity arose. Then came more rocks. And so on and so forth until you find us here today, strolling above layers of buried bones, occassionally casting nervous glances above for giant rocks. Now I’ve read several accounts saying this history of biological diversity was mathematically and/or statistically impossible to have occurred “by chance alone” BWM via RM+NS. DaveScott indicated in his post there wasn’t enough time for the appropriate number mutations to occur, etc. I’ve yet to see those calculations done properly. There is a parallelism inherrent to the real universe that makes doing this analytically, with pen and paper, impossible (so far as I can tell.) (Several have made the mistake of ignoring one or more dimensions (e.g. spatial extension) As I’ve argued elsewhere here, our lack of knowledge concerning parameters and other facts, as well as the shear scale involved, makes computational simulation impossible for the forseeable future as well. Mutation rates and generation time vary considerably across taxa. And bacteria… As a meditation sometime, reflect on the masses of bacteria that have existed, each on their own little evolutionary trajectories, since the dawn of life. Even if you think your combinatoric calculations are adequately accounting for the actual density of gene-trees across the planet over the entire history of life (do you?), there are plenty of other parameter values you don’t have a clue about (b/c I don’t have them, because nobody has them). And there are fluctuations in those parameter values (e.g. mutation rates, population sizes, fitness landscapes) that aren’t even tractable to calculate with analytic methods. So I’d encourage you to check your math. Once its convincing enough, perhaps it will provide that exceptional and overwhelming evidence that will convince people to allow teleological ID arguments to be taught side by side with naturalistic Darwinism in our science classes. (But perhaps not before it battles the naturalistic multiverse theory for a that priveledged spot…). My guess is that you won’t convince the academics any time soon. Biology, unlike physics, has a historical component than is fundamentally interwoven with its diversity and notoriously difficult to express in mathematical terms. That is why we are so fond of modelling these things on the computer and then discussing at length why we don’t trust the models.

    (p.s. Also remember that if you walk outside and begin recording things, such as the succession of makes of models of cars passing by … when you subsequently calculate the odds of witnessing the particular pattern you observed, it will be vanishingly small. But, of course, that *was* the pattern you observed. Certain ways of posing the combinatoric problem concerning evolution fall into pitfalls associated with singular historical events. I haven’t the time to go into this further (or the expertise, honestly) but consider that we are *somewhere* in that vast combinatoric space, and *however* we got there-even via BWM-would seemly ludicrously improbable if we framed the question in certain ways. In much the same way that the course our personal lives have taken would be ridiculously improbable, our particular wardrobe is most certainly ridculously improbable. Darn near every aspect of the world around us would be ridiculously improbable. Something to consider.)

    [[DaveScott's response and "boot message"]]

    If by all that you mean to say that RM+NS is so well proven that the law of the land should require that it be taught in a vacuum devoid of criticism or contrary ideas then I say you’re out of line. In order to gain that kind of cocksureness you’re going to have to do more than just speculate that unpredictable mutations, through serendipity and natural selection over the course of deep time, accumulate to turn bacteria into baboons, create novel cell types, tissue types, organs, and body plans. The theory of gravity has the kind of predictability (inside practical bounds) that warrants uncritical acceptance. NeoDarwinian bacteria to baboon evolution doesn’t even come close. I don’t see anything constructive to further discussion as you aren’t fooling anyone here and I’m sure no one here is going to change your thinking. An hasta la byebye is in order. Don’t let the door hit you on the butt on your way out.-ds

  2. #2 Bruce Thompson
    April 13, 2006

    If droso-ventral flexation is a key element in the transition to land, does this adaptation precede any adaptations seen in the fin to limb transitions? It would seem that the limb transition would be secondary to the flexation mechanism if this is true.

  3. #3 Sean Storrs
    April 22, 2006

    On the April 19, 2006 episode of “The Colbert Report” on Comedy Central, Stephen Colbert mentioned the eel catfish during his “Tip of the Hat, Wag of the Finger” segment saying, and I quote:

    “What looks like a snake has whiskers like a cat and hunts prey in or out of the water? It’s called an eel catfish and it’s getting my ‘Wag of the Finger.’ Look at this freaky thing in action. See it slithers out of the tank to grab a piece of meat on a platform. Eel catfish, by coming out of the water to eat, you’re disturbing the natural order that says fish gotta swim, birds gotta fly and humans need to take every word of The Bible as literal truth. This thing is just another bullet in the Darwin-hugger’s gun. You just know they’re gonna say this proves evolution.” © 2006 Comedy Partners