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Author
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Topic: More on the flagellum and IC
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Mike Gene
Member
Member # 149
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posted 28. April 2002 22:41
Richard Wein criticizes Bill Dembski's calculations concerning the evolutionary origin of the bacterial flagellum as follows:
quote:
Critics were therefore looking forward to seeing the long-promised probability calculation that would support the claim. While I, for one, did not expect a convincing calculation, even I was amazed to discover that Dembski has offered us nothing but a variant on the old Creationist "tornado in a junkyard" straw man, namely the probability of a biological structure occurring by purely random combination of components.
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No biologist proposes that the flagellum appeared by purely random combination of proteins--they believe it evolved by natural selection--and all would agree that the probability of appearance by random combination is so minuscule that this is unsatisfying as a scientific explanation. Therefore for Dembski to provide a probability calculation based on this absurd scenario is a waste of time.
That biologists believe the bacterial flagellum evolved by natural selection may be a function of sociological dynamics and the reigning paradigm rather than a function of the evidence. The "most scientists believe" argument is inherently risky, as one time most scientists also believed that proteins were the genetic material. What matters are the data concerning the flagellum and its origin. Is there evidence that the bacterial flagellum evolved? Is there evidence that the bacterial flagellum evolved by natural selection ? In both cases the answer appears to be no (especially so with the last question) and Wein, not surprisingly, provides none.
Alluding to a web page article, Wein does note that an evolutionary "explanation" has been proposed for the bacterial flagellum, but it is worth noting that he had to allude to a web page article and not something that has passed the peer review process of the scientific literature. This is the just so story about something that begins as a protein secretion device that coincidentally gets gradually turned into a flagellum. I did begin a critique of this hypothesis on my web page [1], as it suffers many problems, but the point here is whether Dembski was really supposed to consider every private vague speculation that gets posted somewhere on the internet? I think not. First it would seem that the non-teleologists worry about getting these speculations into the scientific literature. If such speculations cannot pass the peer review of the non-teleological community, why is Dembski supposed to factor them in?
Of course, the generic complaint is that Dembski employed the "tornado in a junkyard" calculation when he should have been focusing on the step-by-step gradualistic scenario of neo-Darwinism. But is it really this simple? It's good to see that Wein and others recognize that if they have to rely on a "tornado in a junkyard", their position is sunk. But the question then is whether or not such a tornado is lurking behind the non-teleological views of the origin of the flagellum. To simply insist that the step-by-step gradualistic scenario of neo-Darwinism applies in this instance is to beg the question. What Wein needs to do is find the data that indicate the gradualistic accounts are relevant to the origin of the flagellum rather than merely assume they apply in some vague manner (which is too easily interpreted as hand waving). Otherwise, a "tornado in a junkyard" calculation may indeed be a confirmation step.
Concerning the generic issue of IC, Wein writes:
quote:
When it comes to indirect pathways, Behe has nothing but an argument from ignorance: no one has given a detailed account of such a pathway. The truth of this assertion has been contested, but it depends on just how much detail is demanded. Behe demands a great deal. He then asserts that the evolution of an IC system by indirect pathways is extremely improbable, but he has provided no argument to support this claim. It is merely his intuition.
It's not a question of someone inventing an "account," as I don't think IC should be viewed as a test of one's imagination. It's a question of the evidence. Is there evidence to suggest a particular IC system arose through indirect pathways (i.e., cooption). The whole concept of IC thus brings focus, allowing us to zero in on what would be entailed by the step-by-step evolution of something like the flagellum. It is, of course, intuition that leads some us to reach a healthy skepticism about the attempts to invoke cooption without any regard for the facts. Such intuition, however, is informed by what we find in nature and in the lab. For example, we could take bacteria that have no flagella, but do encode ion channels, protein secretion devices, and filaments. We can mutagenize them at high levels and attempt to evolve some type of motility structure (not the canonical flagellum) that makes cooptional use of these components. How likely is one to succeed? That there are no labs trying to bring about such a remarkable result (surely something like this would be the cover story article for Science or Nature ) suggests that the intuition is not Behe's alone.
Wein also notes:
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First, he attempts to show that the flagellum could not have arisen by Darwinian evolution, appealing to a modified version of Michael Behe's argument from irreducible complexity. However Dembski's argument suffers from the same fundamental flaw as Behe's: he fails to allow for changes in the function of a biological system as it evolves.
But why should one allow for change in function if there is no evidence of change in function? Are we really supposed to shoehorn explanations onto reality regardless of the data? Furthermore, it would help if Wein could provide a calculation that gives us a "change in function" frequency (CIFF) as it applies to molecular machines. Without evidence or a CIFF, what is to prevent one from invoking a change in function in a purely ad hoc manner? As far as a design inference is concerned, this is a sure road to a false negative.
Given the great divide that exists between the positions of Wein and Dembski, are their routes of investigation that might help resolve the dispute?
A detailed look at something like the flagellum, and all of its parts, may help to determine to what extent random assembly can be plausibly side-stepped. Are there data to support the notion that the flagellum arose by incrementally adding one (or two) gene products at a time, guided by selection retaining "functions" that just happened to increase fitness in some way?
We can also attempt a guess at the CIFF. Luckily, most change in functions are coupled to gene duplications, meaning that a change in function may be detected by the existence of homologs not involved in flagellar function. We can score these homologs across phylogenetic distances, trying to estimate how often flagellar genes have changed their function over time. This CIFF estimate, in turn, can be applied to an estimate of the amount of time it took to evolve the flagellum. Such findings can be coupled to the experimental results I suggested above.
[1] My web page is currently being re-designed. I will eventually upload the flagella articles, along with several more.
[ 30 April 2002, 10:28: Message edited by: Mike Gene ]
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Mister Pamboli
Member
Member # 175
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posted 29. April 2002 13:17
Firstly, I'm not sure how this topic fits in to the Brainstorms thread as it doesn't really propose anything - Mike just criticizes Wein's approach to IC. quote:
That biologists believe the bacterial flagellum evolved by natural selection may be a function of sociological dynamics and the reigning paradigm rather than a function of the evidence. The "most scientists believe" argument is inherently risky, as one time most scientists also believed that proteins were the genetic material. What matters are the data concerning the flagellum and its origin.
This is a good point, but is also inherently risky - what constitutes "the data", how complete that data is, and most importantly how that data is contextualized for analysis is just as paradigmatic and dependent on the social dynamics of the moment. Indeed, once could say this is the very reason the flagellum is part of the current discussion at all - the entire debate moves its focus with the paradigm of the day. No one should dare claim an unclouded vision of the data: neither Dembski nor Wein can do so. quote:
To simply insist that the step-by-step gradualistic scenario of neo-Darwinism applies in this instance is to beg the question. What Wein needs to do is find the data that indicate the gradualistic accounts are relevant ... Otherwise, a "tornado in a junkyard" calculation may indeed be a confirmation step.
This does not really take us any further than the by-now-traditional "show me a pathway" v "show me a designer" level of debate. Actually, to be fair to Mike, he comes close to an important point, that gradualists should show that their approach is relevant, but I think he undermines this later with ... quote:
It is, of course, intuition that leads some us to reach a healthy skepticism about the attempts to invoke cooption without any regard for the facts. Such intuition, however, is informed by what we find in nature and in the lab.
Wein could rightly argue that it is informed intuition - informed by the pathways that have been discovered for other complexities - that indicates that gradualistic accounts are likely to be relevant.
The important point Mike get's close to raising, but doesn't quite get to, is this:
Given the existence of flagella - which inductive strategy will most reliably converge to a true explanation of their origin while maintaining a best fit to observations during the (possibly endless) investigation?
This is possibly worth another thread - I'm v. busy at the moment, but if I get time I'll see if I can start one off.
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Moderator
Administrator
Member # 1
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posted 29. April 2002 14:40
Mike,
I agree with Mister Pamboli on this one. Your critique of Wein would be fine in light of a clearer positive argument. Perhaps just adding a paragraph to your post providing a positive direction to the thread would do the job...
Thanks.
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Mike Gene
Member
Member # 149
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posted 30. April 2002 10:40
Moderator, I added some suggestions for ways to resolve this dispute. If this is not sufficient, let me know, and I'll delete and reformat the essay. I'll try to be more careful.
Mister P: Wein could rightly argue that it is informed intuition - informed by the pathways that have been discovered for other complexities - that indicates that gradualistic accounts are likely to be relevant.
Wein could argue this, but I'm not sure he could rightly argue this. Relevance is a function of the validity of the extrapolation. And I don't think it a good idea to smear biotic features into a vague notion of "complexities," as not all "complexities" are the same. For example, a commonly cited "complexity" whose pathway has been crudely outlined is the evolution of the mammalian middle ear. But a closer look will show that attempts to extrapolate this event to the origin of something like the bacterial flagellum are highly questionable, at best. Thus, to resolve this dispute, folks like Wein would have to put the "discovered" pathways on the table, which is why I often invite the most impressive example of such a discovery for analysis. From there we can compare and contrast to get a feel for what is being assumed by such an extrapolation.
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