Freethought & Rationalism Archive

tgamble · 04-09-2003, 12:24 PM

Any comments?
http://www.iscid.org/papers/Dembski_...ing_030403.pdf

He makes some interesting claims not the least of which is this one.

"There's another problem here. The whole point of bringing up the TTSS was to posit it as an evolutionary precursor to the bacterial flagellum. The best current molecular evidence, however, points to the TTSS as evolving from the flagellum and not vice versa (Nguyen et al. 2000)."

NialScorva · 04-09-2003, 01:12 PM

I know nothing about biology, much less microbiology, but I'll place my bet on "misrepresentation, misquotation, and/or misunderstanding primary literature."

I could be wrong, though.

Principia · 04-09-2003, 01:24 PM

Try the discussion here. And, of course, follow nic's links.

Non-praying Mantis · 04-09-2003, 02:10 PM

OK, let me see if I can figure out where Dembski is coming from:

Quote:

Originally written by Dembski
Getting from Irreducible Complexity to Design:
Miller, in line with his personal incredulity criticism, charges design proponents of reasoning directly from the premise "Shucks, no one has figured out how the flagellum arose" to the conclusion "Gee, it must have been designed." Miller, despite a long exposure to ID thinkers and their writings, continually misses a crucial connecting link in the argument.

Let's see that "missing link" in Miller's thought process:

Quote:

So let me spell out the premises of the argument as well as its conclusion: Certain biological systems have a feature, call it IC (irreducible complexity). Darwinians don't have a clue how biological systems with that feature originated (Miller disputes this premise, but we'll come back to it). We know that intelligent agency has the causal power to produce systems that exhibit IC (e.g., many human artifacts exhibit IC). Therefore, biological systems that exhibit IC are likely to be designed. Design theorists, in attributing design to systems that exhibit IC, are simply doing what scientists do generally, which is to attempt to formulate a causally adequate explanation of the phenomenon in question.

er...yeah...right

Miller is "obviously" missing something: that something is the "property" of IC, which Dembski elaborates on below:

Quote:

Irreducible Complexity Is Not Properly Ascribed to the Bacterial Flagellum:
According to Miller, Behe's claim that the bacterial flagellum is irreducibly complex is false. If Miller is right, then Behe and the intelligent design movement are in deep trouble.

You can say that again, Dembski!

Quote:

(italics in original)
Think of it: Behe goes to all this bother to formulate some feature of biochemical systems that is a clear marker of intelligent agency and that decisively precludes the Darwinian mechanism. Behe then asserts that the bacterial flagellum exhibits that feature. Rather than argue about whether that feature reliably signals design or effectively precludes Darwinism, Miller claims to show that when it comes to the design community's best example of irreducible complexity -- the bacterial flagellum -- that it isn't even irreducibly complex. What idiots these design theorists must be if they can't even apply correctly the very concepts they've defined!

[sarcasm]
Oh, no! Behe went to all of that bother! Therefore, he can't be wrong about IC existing! Could he???
[/sarcasm]

I especially like Dembski himself calling design theorists "idiots!" Poetic justice, if you ask me!

NPM

theyeti · 04-09-2003, 02:55 PM

Quote:

Originally posted by tgamble

"There's another problem here. The whole point of bringing up the TTSS was to posit it as an evolutionary precursor to the bacterial flagellum. The best current molecular evidence, however, points to the TTSS as evolving from the flagellum and not vice versa (Nguyen et al. 2000)."

Unfortunately for Dembski, the question of which came first is not the relevant issue. What the TTSS demonstrates is that it's possible to have a functioning selectable system that is derived from (or a precursor to) the flagellum without needing to have the whole thing all at once. Even if the modern TTSS is derived from the flagellum, there is no reason to discount automatically the possiblity that the flagellum was derived from an earlier secretion system or some similar system. The problem is that Dembski's argument absolutely relies on there being no possible precursor systems from which the flagellum could be derived; in other words, no possible intermediate steps. The existence of the TTSS shows that there are potential intermediate steps, and that Dembski's failure to account for this makes his claims untenable.

theyeti

Albion · 04-09-2003, 10:06 PM

Well, that Nguyen et al reference is three years old. Is there any recent information about the relationship between the TTSS and the flagellum?

theyeti · 04-10-2003, 07:05 AM

Quote:

Originally posted by Albion
Well, that Nguyen et al reference is three years old. Is there any recent information about the relationship between the TTSS and the flagellum?

Well, I thought I'd do a quick pubmed search and I turned up this:

J Biol Chem 2003 Feb 5; [epub ahead of print]

Helical structure of the needle of the type III secretion system of Shigella flexneri.

Cordes FS, Komoriya K, Larquet E, Yang S, Egelman EH, Blocker A, Lea SM.

Quote:

Gram-negative bacteria commonly interact with animal and plant hosts using type III secretion systems (TTSSs) for translocation of proteins into eukaryotic cells during infection. Ten of the twenty-five TTSS encoding-genes are homologous to components of the bacterial flagellar basal body which the TTSS needle complex morphologically resembles. This indicates a common ancestry although no TTSS sequence homologues for the genes encoding the flagellum are found. We here present a ~16 structure of the central component, the needle, of the TTSS. Although the needle subunit is significantly smaller and shares no sequence homology with the flagellar hook and filament, it shares a common helical architecture (~5.6 subunits per turn, 24 helical pitch). This common architecture implies that there will be further mechanistic analogies in the functioning of these two bacterial systems.

So it appears that the TTSS and flagellum share additional structural homology byond the basal proteins. Just more problems for Dembski. (I'll repost this at AE for Nic's benefit.)

theyeti

04-09-2003, 12:24 PM	#1
tgamble Veteran Member Join Date: Sep 2000 Location: St. John's, Nfld. Canada Posts: 1,652	Dempski vs. Miller Any comments? http://www.iscid.org/papers/Dembski_...ing_030403.pdf He makes some interesting claims not the least of which is this one. "There's another problem here. The whole point of bringing up the TTSS was to posit it as an evolutionary precursor to the bacterial flagellum. The best current molecular evidence, however, points to the TTSS as evolving from the flagellum and not vice versa (Nguyen et al. 2000)."

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04-09-2003, 01:12 PM	#2
NialScorva Veteran Member Join Date: Jan 2001 Location: Median strip of DC beltway Posts: 1,888	I know nothing about biology, much less microbiology, but I'll place my bet on "misrepresentation, misquotation, and/or misunderstanding primary literature." I could be wrong, though.

04-09-2003, 01:24 PM	#3
Principia Veteran Member Join Date: Mar 2002 Location: anywhere Posts: 1,976	Try the discussion here. And, of course, follow nic's links.

04-09-2003, 10:06 PM	#6
Albion Veteran Member Join Date: Jul 2002 Location: US east coast. And www.theroyalforums.com Posts: 2,829	Well, that Nguyen et al reference is three years old. Is there any recent information about the relationship between the TTSS and the flagellum?

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