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Khylov β Acanthostega and Polydactyly
Published: 2008-05-18 16:37:24 +0000 UTC; Views: 5251; Favourites: 30; Downloads: 822
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From the original blog post:Ahhhh, Good ol' Acanthy; the mainstay of the Darwinian hypothesis for probably the last two decades or so. A funky kind of chimera tetrapod, with multiple digits on its fore (and presumably hind) limb. Awwwww.....
I'm of the thought that Acanthostega - besides being a chimeromorph of sorts - exhibited a Hox gene malfunction in the doubling of its digits...
Also known as polydactyly, it is not uncommon even for modern day organisms (most notably amphibians) where digits and even whole appendages are doubled, due to a malfunction/mutation in the genes which code for proper limb placement. These genes are known as Hox genes, and essentially do the job of plugging in where exactly an antenna, limb, or leg goes. Remember news reports several years back about geneticists getting a fruit fly to grow legs where its antennae should've been? Hox genes at work (or *out to lunch*, presumably)...
There's more on this at my blog, including more artwork:
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And as an added bonus, special guest appearance in the comments below by Pristichampsus , champion of the science fetish and akratic extraordinaire.
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Comments: 32
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No mention here of HOX genes having anything to do with vertebrate polydactyly. Seems you may be simply an arrogant creationist assuming that one mutation that works for one creature, works for another. Hox mutations produce multiple segments in a head-to-tail sequence, it can effect ribs and body segmentation, there is no mention of it producing supernumerary limbs or digits.
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So you mean to tell me that polydactyly or hyperphalangy are in fact de novo? Or that digits don't currently multiply beyond a normal digit count, due to a biochemical phenomena we observe at present? (Google Hox or "SHh" (Sonice Hedgehog). Pictures in a number of articles show supernumerary digits in fair abundance in relation to the term.)
It's interesting how science fetishists are extremely selective about what hypothetically could happen in the unobservable past, even with documented processes.
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Okay, it can occur through hox-gene mutations. However, do you know how vastly unlikely it is that a rare pathological mutant would be found in the fossil record? I can only think of one instance where such a thing has been observed. The proposed reason why primitive tetrapods have multiple digits is because they are derived from multiple fin-rays, this seems simple enough to me. Also, I think transitional forms as seen in the fossil record is far more feasible than the crackpot idea of yours that god created "chimeras", especially the platypus, how is it a chimera if the bill of a platypus is in no way analogous to a bird's beak? If anything, being soft, sensitive, and full of electrosensory organs, would make it more qualified as being part shark.
Also, you seem to be yet another arrogant creationist, making obtuse observations about science adherents and referring to them as fetishists.
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"Okay, it can occur through hox-gene mutations."
And thus the hand waving after the fact. In other words, even when observable scientific evidence is involved, you're wrong. And I'm supposed to place a tacit amount of trust in your other speculations on what can or can't happen, mutationally speaking.
At this point, I think I can safely assume that you're not to be taken seriously from here on out.
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Did some more searching, seems that you weren't lying or bluffing. But honestly, can you BLAME me for being suspicious? You're the one that believes a giant sky wizard poofed the world out of nothingness.
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I can't blame someone for acting like an Aspergerite, no.
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You are a real piece of work.
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Now this made my day, sir. I'm framing this somehow onto the main page whenever I care enough to upgrade the account.
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Interesting.
But if this little guy did develop its many fingers as a result of a mutation (and we've simply found all of the mutants), how could it have come about? Last time I checked, a good deal of Hox mutations come about via chemicals or some kind of foreign material, like the many-limbed frogs growing in polluted swamps.
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As a palaeontologist who did my thesis on Acanthostega I would like to point out that you, sir, are a moron. You do realise that there are a variety of late Devonian tetrapods that exhibit not only 5, but 6 or 7 digits on each limb, as well as Acanthostega's 8. Evolution is a fact, if you did some actual reading, you'd see that too.
Nice picture though.
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Remember, an empty vessel makes the most noise, which seems apt in this case, seeing as how this person gloats. I'm with you on this, but since when do creationists actually listen???
All accepters of evolution will eventually need to also accept that convincing creationists is about as effective, and enjoyable, as firing nails into your forehead to cure a headache.
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Well, let's see: Given Shubin's own words, inducing ZPA with retinoic acid will tend to duplicate digits (or even whole limb structures) opposite where the patterning normally develops. (This seems to be somewhat independent of SHh signaling, although I may be wrong on that.)
But within that explanation, there's no observable experiment as to where or how exactly any of that complex information arose in any materialistic/Darwinist manner (including SHh patterning and timing, which is pretty specific if things are to work correctly during development).
So, on the one hand, we have a pretty mundane explanation as to how an organism which had all the attendant complexity to begin with can exhibit polyphalangy or the like (which Acanthostega seems to bear, for all our actual observations) - and on the other hand, we have a non-observable just-so (and tax funded) story as to how an organism like Acanthostega bioengineered itself (and a whole host of other complex features) through a conserving or detrimental mechanism (natural selection), and all from ultimately a de-novo state. (For after all, a tetrapod from a fish from invertebrate from bacterium from... a rock. And that from an explosion of nothing, on it's own! Very scientific...)
And apart from Ichthyostega or Tiktaalik, I can't think of any other tetrapod examples that exhibited polyphalangy or anything of the sort. Unless you're including crossopterygians into that category - which is just as reasonable as saying that since cetaceans, chicken embryos, and circus freaks exhibit mutations to various limbs, they should be included in this grand Darwinian phylogeny as well. And why not? since superficial similarities are all that we're really appealing to when building those impressive looking cladograms and family trees...
As a Paleovolkischer who seems to find a need to spread the Darwin Gospel on deviantart, you're ecstatic whirling dervish ode to extinct organisms is dually noted. Best of luck with your thesis and grant-hunting career.
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Ups, completly forgot about phalanges on fishpods, sorry
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No prob; thanks for the reply.
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Polydactyly isn't a particularly common phenomenon among living tetrapods. Besides, the toes/fingers of these fishpods are relatively simple compared to the phalanged toes of modern tetrapods; even lissamphibians have phalanges, while those are just like as if they came from fin rays
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Well, that's one interpretation over this organism's physiology, and that's fine - everyone's entitled to their own beliefs over historical proposals, especially when it comes to bauplans and morphology. But the comment about polydactyly not being common among tetrapods - hmm, pretty sure that if you look up any PubMed reference regarding SHh or Hox genes in relation to digits, you'll see fairly well documented studies (and pictures) of polydactyly in effect - even a google search under the term will give you fairly numerous examples and photos.
If your talking about it being fairly rare among amphibians, then yes, I'd think it not as common, although not without precedent. Again, google to the rescue with some photo reference of frogs exampling repeated limbs; and while not exactly polyphalangy, it does show a similar Hox phenomena in effect.
Besides, can we with 100 percent certainty rule out polyphalangy in the past for tetrapods? If not, then the proposal that Acanthostega is exampling multiplying of digits off an otherwise normal tetrapod count is as tenable as any Darwinian interpretation - more so I'd think, since a Hox gene malfunction is a bit more down to earth (of which we have modern day parallels) rather than the hypothesis that Acanthostega is an offshoot branch of rhipidistians, crossopterygians, or which ever is the new proposed lineage.
I haven't had time to give a more in-depth response to your comments up to now, but I've been meaning to dust up on the Tiktaalik paper in my archives over the points you raised earlier, about cranial morphology. In any event, just to give fair warning: homological arguments - while the standard fare for evo papers - don't "wow" me the same as they may do for others. I think for me it's the idea that, for one, these proposals aren't testable, repeatable, or measurable in real time - in other words, not verifiable by operational science. (Which isn't bad per se, but just something to consider when a proposal is presented as purely scientific rather than a hypothetical guess.) ...For another, homology can just as easily be applied to man-made (or intelligently designed) objects - from cars and kitchen ware, and still turn out nice neat little cladograms showing the Darwinian change of Model T's and bowls into their modern bauplan manifestations - Corvettes and sporks. I honestly think that homology is a form of interpretation over objects or organisms that, in the end, only exists most times within the minds of men.
In any event, I didn't intend for this to go on as long as it has. I'm sure we'll exchange thoughts over this in the proceeding weeks or what have you - in which case, be patient for a reply if I can get back online with any regularity. Thanks again for commenting and dropping by - the interest is much appreciated. Cheers.
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Gorgeous drawing. The drawing of the skeleton is especially well constructed.
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Is tough to reconstruct the spine and shoulder blades with only 2D references, so I'm glad someone dug on how it was put together. Cheers.
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wowowo...this is pretty cool...i have to say that i am not versed in...smartstuff...so i pretty much just skimmed it,but it's one hell of a beautiful image
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Cool cool, thanks. I think having the scan come out with a saturated bg (and w/ paper grain) helped the color palette out a bit. That, and doing the original sketch on portfolio binder paper... (Hey, whatever works, right?)
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it's fantastic! i love looking at your work...so detailed and lively!
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Too kind; you're too kind. :]
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Not nearly enough XDD
PERHAPS...this is not the ideal place to bring this up...but i read your journal and it gave me lots of things to think about....i wonder if you wouldn't mind me hassling you sometime about your knowledge...you seem to be doing what i WANT to be doing, and i want to know how you went about getting there!
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Sure thing; drop one in the mailbox when you're ready.
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thanks! it has...BEEN DONE 8O
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So, let's see... you give the textbook explanation verbatim of the proposed phylogeny of tetrapods. In other words, an interpretation that's placed upon the fossil evidence - the hypothesized (yes, hypothesized) historical scenario which Darwinism forwards, and of which cannot be observed, measured, or repeated in any meaningful operational scientific way (conveniently enough for the hypothesis).
"Primitive tetrapods with multiple fingers and toes appear to have been largely restricted to aquatic environments."
Right, and no one's arguing that here - I figured the picture of all organisms in question swimming in water would've made that obvious (well, to most folks anyhow). The land bearing mechanics of acanthostega's limbs has been brought up by creationist commentators such as Gardner and others -which is why the polydactyl condition here probably wasn't so much of an impediment on the creature: If it's obligate aquatic, polydactyl digits may have been helpful in its ecological niche (paddle for swimming, etc).
"After the five-fingered varieties evolved in the Carboniferous, they diverged rapidly to give rise to most of the major groups in less than 30 million years..."
And why I call it the Darwinian *hypothesis*. You can't duplicate any of these proposals in a lab setting. Given the imagined timeframe, there's no feasible way anyone could observe macro evolution occurring (over millions of conveniently unobservable years). Even if known genetics didn't mitigate against it already, you wouldn't be able to see this fortuitous circumventing of known natural laws while wholly new bauplans, biochemical machinery, and interrelated new forms of breathing, reproducing, and locomotion arrive in a Darwinian sense.
So, you're left with some broad sweeping statements that, unfortunately, can only be relegated to "We guess", "We suppose", or "Here's a neat story for you...", etc. In other words, a hypothesis. Which is fine; I just think such proposals ought to be classified as another branch of research other than βoperational scientific biologyβ. Maybe βorigins hypothesesβ, or βhistoric proposals for paleontologyβ.
I cover more aspects of the technical considerations on the blog entry connected to this, specifically the branching radials proposals, as well as briefly discussing the larger problems associated with the host of other biomechanical and biochemical issues that Darwinists tend to skim over in the fish/tetrapod scenario (such as how obligate aquatic respiration that's dependent on several interlinking biomechanical factors can somehow switch fortuitously into a completely new mode of terrestrial respiration).
I think I'm a fairly open minded guy, and I can to some extent understand when Darwinists feel a need to proselytize their faith on other people's pages, even when uninvited. But fair warning: No more smart ass statements, or you'll end up in the spam box.
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Thanks, yo; much appreciated.
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Right on; *high five* (or, *high eight*; whatever applies to an amphibian with several fingers...)
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I am not more than passingly familiar with acanthostega, but I take it that this little critter is considered in some way a "missing-link" between fin-bearing fish and finger-bearing amphibians (and beyond?)
Interesting.
Your take on it being a unique instance of genetic mutation (on an already finger-bearing animal) as opposed an evolutionary step in freeze-frame makes a lot of sense.
Wow, intelligent discourse!!! ...consider your Blog "watched"
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Quite the compliment; thank you friend.
(I've since gone back and reworked a little of the original article. Is always one of those things where one thing adds to another, new avenues open up, and more things need to be clarified in the process. (!)
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