Darwinist disdainfulness
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Paleontologist Neil Shubin has made a big deal about the claim that Tiktaalik roseae, supposedly a transitional fossil between fish and tetrapods, has "wrist" bones in its limbs, but Casey Luskin complained that he was unable to find diagrams of these wrist bones in Shubin's literature about the fossil: the book "Your Inner Fish" and scientific papers. Sleazy PZ Myers then posted articles -- on both Panda's Thumb and his own Pharyngula blog -- containing the above comparative diagram of Tiktaalik's and tetrapods' limb bones, but instead of saying politely, "here is the diagram you were looking for, Casey," Sleazy PZ ridiculed Casey. Carl Zimmer also attacked Casey and Fatheaded Ed Brayton had to get in his licks, too. Yet another blogger attacked Casey. If this "wrist" homology is so important, then why didn't Shubin's literature have diagrams of it? Also, why are the bones labeled "radius," "ulna," "ulnare," and "intermedium" in the above diagram considered to be "wrist" bones? In humans, the "radius" and the "ulna" are "forearm" bones. It appears that only one of the limbs in the diagram, the rightmost limb, is shown as having bones that are homologous with human wrist bones -- these bones are labeled "other wrist bones," but they might just be "digits" bones.
Labels: PZ Myers
posted by Larry Fafarman | 7/18/2008 03:45:00 AM
9 Comments:
So are you just upset at how PZ Myers chastized Casey Luskin or you do agree with Casey that wrist bones are missing? What's your point?
As far as I can see, Larry and Luskin both think that the concept that both Tiktaalik and tetrapods have bones in the 'wrist' that are named the same is such a complicated one it requires a diagram, and is upset with PZ Myers, et al, for poking fun at Luskin when he complains that Shubin doesn't name the bones in the Tiktaalik, when, in fact, Shubin says that the bones are 'eponymous wrist bones of tetrapods'. In other words, they are named after the bones in tetrapods - they have the same names. He also tries to make some sort of point about how the bones are mislabeled as they are labeled the same as bones that are in the forearm of humans, rather than the wrist. Newsflash - tetrapods and Tiktaalik aren't humans.
Anonymous I said...
>>>>> So are you just upset at how PZ Myers chastized Casey Luskin or you do agree with Casey that wrist bones are missing? <<<<<<
Well, some of both.
Anonymous II said...
>>>>> As far as I can see, Larry and Luskin both think that the concept that both Tiktaalik and tetrapods have bones in the 'wrist' that are named the same is such a complicated one it requires a diagram <<<<<<
Ever hear the expression, "a picture is worth a thousand words"? Do you think that scientific literature should have no pictures? And one of Casey's complaints was that the book "Your Inner Fish" had a picture of the skull comparison but no picture of the wrist bones.
>>>>>>. . .and is upset with PZ Myers, et al, for poking fun at Luskin when he complains that Shubin doesn't name the bones in the Tiktaalik, when, in fact, Shubin says that the bones are 'eponymous wrist bones of tetrapods'. In other words, they are named after the bones in tetrapods - they have the same names. He also tries to make some sort of point about how the bones are mislabeled as they are labeled the same as bones that are in the forearm of humans, rather than the wrist. Newsflash - tetrapods and Tiktaalik aren't humans. <<<<<<<
Well, internal-combustion engines are not human, either, but piston pins are sometimes called "wrist" pins because of functional similarity to human wrists, the only difference being that the wrist pin allows pivoting in only one plane.
I am saying that the name "wrist bones" may be inappropriate in these fossils because these bones are functionally different from wrist bones in humans. The human wrist functions like a ball joint or universal joint but these so-called "wrist" bones in the fossils only allow twisting of the limbs around their axes and maybe some pivoting too if the end joints function like elbows, and in Tiktaalik, the amount of twisting allowed would be very limited. Also, the humerus bones in these fossils may be functionally different from the humerus bone in humans -- in humans, the humerus bone pivots around a ball joint at the shoulder but in these fossils the humerus might just be a fixed connection between the limb and the rest of the skeleton.
Larry posits: "but these so-called "wrist" bones in the fossils only allow twisting of the limbs around their axes and maybe some pivoting too if the end joints function like elbows, and in Tiktaalik, the amount of twisting allowed would be very limited."
1) I'd really, really, really like to know how you *know* what these fossil anumals could or could not have done. Please cite your source(s).
2) I'm having a hard time making out exactly what it is the diagram you displayed is trying to "prove". My interpretation is that the drawings on the left are earlier fossils than the drawings on the right, and if so, looks like it supports evolution to me. If I'm wrong, please explain to me, to us all, what we are looking at. If you don't actually know, it's hardly a good piece of evidence for any position, is it?
3) Shublin did apparently provide a diagram of Tiktaalik in the scientific journal (from Luskin's own article, sorry, link from Larry's post above):
"1. Shubin et al.: "The intermedium and ulnare of Tiktaalik have homologues to eponymous wrist bones of tetrapods with which they share similar positions and articular relations." (Note: I have labeled the intermedium and ulnare of Tiktaalik in the diagram below.)"
and since he was writing to his colleagues, he figured they'd know exactly what he was talking about, i.e., they all perfectly well knew the names of the bones in tetrapods, and could summon the analogy in their minds, their imaginations!
3) Do we have any reports of scientists questioning Shublin's findings of this?
4) Once more, what is your point, Larry? What are you trying to say? Is it "Shubin should have put a diagram in his book!". OK, sure, maybe you're right, but then the response is simply, "Yeah, a diagram would have been nice". But if you are'nt satisfied with that, then:
5) what is *really* your point? Be a man, Larry, come out and say it. Do you think the guy was lying about his fish? Do you not believe it's a transitional fossil? What?
(my apologies if this posts twice. I have more trouble with this Google blogging thingy)
Anonymous said,
>>>>> I'd really, really, really like to know how you *know* what these fossil anumals could or could not have done. Please cite your source(s). <<<<<<
My source is common sense. The structures of bones often indicate their functions. The function of a ball joint is obvious. The human ankle is obviously a hinge joint. Two long bones that are side by side, e.g., the radius & ulna and the tibia & fibula in humans -- allow a twisting motion. Wrist bones are small bones that work like a universal joint by gliding over each other. There are no bones in the above diagram that appear to be homologous with the human wrist. The "wrist" bones of Tiktaalik look like they allow little if any motion.
>>>>>> My interpretation is that the drawings on the left are earlier fossils than the drawings on the right, and if so, looks like it supports evolution to me. <<<<<<<
I'd really, really, really like to know how you *know* that the drawings on the left are earlier fossils than the drawings on the right. Please cite your source(s).
>>>>> Shublin did apparently provide a diagram of Tiktaalik in the scientific journal <<<<<<
But Luskin complained that Shubin did not show tetrapod limb skeletons for comparison.
>>>>>> Once more, what is your point, Larry? What are you trying to say? Is it "Shubin should have put a diagram in his book!". <<<<<<
Yes, he should have put a diagram in his book. It was not a text-only book -- Luskin said that it had a diagram of a skull comparison. Shubin considered the "wrist" feature to be especially important and the book should have had a comparative diagram for this feature.
>>>>>> Do you not believe it's a transitional fossil? <<<<<<
I can't comment on that without seeing fish fin skeletons. The diagram should include fish fin skeletons for comparison.
Also, some evolutionary leaps are just too great to be bridged by transitional forms.
"The "wrist" bones of Tiktaalik look like they allow little if any motion."
Getting fossilized tends to be even worse than arthritis.
"Also, some evolutionary leaps are just too great to be bridged by transitional forms."
Such as the one leading to your irrationality.
>>>Ever hear the expression, "a picture is worth a thousand words"?<<<
Yes, but is it worth five? That's how many it took Shubin to explain the concept.
>>>Do you think that scientific literature should have no pictures?<<<
I think they should - when it is appropriate. However, unlike you, apparantly, I do not think a scientific publication such as this should litter itself with diagrams illustrating basic ideas that could be covered in five words.
>>>I am saying that the name "wrist bones" may be inappropriate in these fossils because these bones are functionally different from wrist bones in humans. The human wrist functions like a ball joint or universal joint but these so-called "wrist" bones in the fossils only allow twisting of the limbs around their axes and maybe some pivoting too if the end joints function like elbows<<<
So, what you're saying is that they should not be called 'wrist bones' because, although they allow wrist-like movement, they do it in a slightly different way.
>>>and in Tiktaalik, the amount of twisting allowed would be very limited.<<<
'Transitional form' ring a bell? It shows a mid-stage between pure fins, which basically moved as one, and the multi-digited, wristed limbs we see on many animals today, including ourselves. As such, it had wrists, but ones that only allowed more limited movement than modern wrists do.
>>>Also, the humerus bones in these fossils may be functionally different from the humerus bone in humans -- in humans, the humerus bone pivots around a ball joint at the shoulder but in these fossils the humerus might just be a fixed connection between the limb and the rest of the skeleton.<<<
Similar point to the above - of course it's different. Tiktaalik is at a different stage of evolution, at a very different time in history. The fact it's bones and skeleton function in slightly different ways is absolutely no surprise whatsoever.
>>>>> However, unlike you, apparantly, I do not think a scientific publication such as this should litter itself with diagrams illustrating basic ideas that could be covered in five words. <<<<<
No, a picture is important here. If a picture is not important, then why did Sleazy PZ Myers present a picture?
>>>>>> So, what you're saying is that they should not be called 'wrist bones' because, although they allow wrist-like movement, they do it in a slightly different way. <<<<<
I didn't say that they look like they allow wrist-like movement. As I said, the human wrist acts like a ball joint or a universal joint.
>>>>>>As such, it had wrists, but ones that only allowed more limited movement than modern wrists do. <<<<<<
The bones called "wrists" in the fossils are structurally and functionally different from human wrist bones.
>>>>>> Tiktaalik is at a different stage of evolution, at a very different time in history. The fact it's bones and skeleton function in slightly different ways is absolutely no surprise whatsoever. <<<<<<
Yes, but giving these fossil bones the same names as human bones that are structurally and/or functionally different creates confusion. And these differences in structure and function make pictures especially important.
>>>>No, a picture is important here. If a picture is not important, then why did Sleazy PZ Myers present a picture?<<<<
It's that whooshing noise again. The point of PZ Myers supplying the diagram was twofold:
1) To illustrate, in breathtaking detail, how stupid Luskin had been, and;
2) To illustrate how pointless supplying a diagram would be, considering how much space it wastes illustrating a simple point that was addressed in five words.
>>>>I didn't say that they look like they allow wrist-like movement. As I said, the human wrist acts like a ball joint or a universal joint.<<<<
No, all you did was describe movement very much like the movement of a wrist, then say that's the movement allowed by the 'wrist' of these organisms. The only thing missing from that is that the human wrist allows a very slight side-to-side movement which these joints, according to you, don't allow. However, not only is this covered by the newsflash given to you above (that tetrapods and Tiktaalik aren't humans), but, looking at that and comparing it to a human wrist, it is not inconceivable that some of these organisms also had a limited side-to-side movement (though probably not even as much as humans do).
>>>>The bones called "wrists" in the fossils are structurally and functionally different from human wrist bones.<<<<
Sorry, nope. From what I can see, whilst there is quite a bit of difference, there are also striking similarities, in both structure and function.
>>>>Yes, but giving these fossil bones the same names as human bones that are structurally and/or functionally different creates confusion. And these differences in structure and function make pictures especially important.<<<<
Addressed above.
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