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Here’s the challenge:
About a year ago, I read Why Intelligent Design Fails – A Scientific Critique of the New Creationism (edited by Matt Young and Taner Edis). Chapter 5 of that book was contributed by Ian Musgrave and is titled “Evolution of the Bacterial Flagellum.” Targeted as a response to Michael Behe and William Dembski, Musgrave attempts to dispel of the notion of irreducible complexity once and for all. Reading his chapter, I recall being deeply unimpressed. On page 82 of the book, Musgrave offers us the following argument:
Here is a possible scenario for the evolution of the eubacterial flagellum: a secretory system arose first, based around the SMC rod and pore-forming complex, which was the common ancestor of the type-III secretory system and the flagellar system. Association of an ion pump (which later became the motor protein) to this structure improved secretion. Even today, the motor proteins, part of a family of secretion-driving proteins, can freely dissociate and reassociate with the flagellar structure. The rod- and pore-forming complex may even have rotated at this stage, as it does in some gliding-motility systems. The protoflagellar filament arose next as part of the protein-secretion structure (compare the Pseudomonas pilus, the Salmonella filamentous appendages, and the E. coli filamentous structures). Gliding-twitching motility arose at this stage or later and was then refined into swimming motility. Regulation and switching can be added later, because there are modern eubacteria that lack these attributes but function well in their environment.(Shah and Sockett 1995). At every stage there is a benefit to the changes in the structure.
Indeed, Mark Pallen and Nick Matzke make a very similar argument in their 2006 Nature Reviews article (a paper which was raised by an audience member during the recent UK Behe tour). Ken Miller is also reputed for routinely making similar claims regarding the flagellum’s evolution from the Type III Secretion System based largely on considerations of protein sequence homologies.
So, do these points succeed in laying to rest that pesky business of intelligent design once and for all? Well, actually no; they don’t. In fact, I submit that the arguments of all of the aforementioned gentlemen fundamentally trivialize several important issues.
You have to read the whole post for his response.
Here is the conclusion:
Why the Flagellum Evolution From the T3SS Doesn’t Work
One might have thought that the description given above should be more than enough to render the hand-waving gestures of Kenneth Miller et al. trivializations in the extreme. But it gets even worse for the Darwinian story. Why exactly is flagellum biosynthesis so tightly regulated and orchestrated? Not only do the energy demands render the flagellum an extremely expensive system to run, but untimely expression of flagellum proteins may induce a strong immune response in the host system, something no bacterium wants to do.
What is the significance of this from the standpoint of evolutionary rationale? Well, flagellin monomers are somewhat potent cytokine inducers. If you are a Yersinia organism in possession of a Type-III Secretion System the last thing you want to do is display those flagellin peptides to the macrophages. Such would be liable to significantly countermand the Yersinia’s anti-inflammatory strategy.
My description, given above, has really only scratched the surface of this spectacular item of nano-technology (for more detail, see here). I have not, for the sake of brevity, even discussed the remarkable processes of chemotaxis, two component signal transduction circuitry, rotational switching, and the proton motive force by which the flagellum is powered (for details on this, see my discussion here or, for more detail, see this review paper). But the bottom line is that modern Darwinian theory — as classically understood — has come no where close to explaining the origin of this remarkably complex and sophisticated motor engine. Just as Darwinian “explanations” of the eye may, at first, appear convincing to the uninitiated, largely unacquainted with the sheer engineering marvel of the biochemistry and molecular basis of vision, so too do the evolutionary “explanations” of the flagellum rapidly become void of any persuasiveness when one considers the molecular details of the system. When one couples the above details with demonstrations of the sheer impotence of neo-Darwinism to produce novel protein folds and novel protein-protein binding sites, do you really think that this system can be cobbled together by virtue of slight, successive modification, one small step at a time? Given that neo-Darwinism’s key selling point lies in its purported efficacy in explaining away the overwhelming appearance of design, doesn’t it stand to reason that its demonstrable impotence throws the design postulate back on the table as a viable and respectable scientific proposition?
Douglas Axe of the Biologic Institute showed in one recent paper in the journal Bio-complexity that the model of gene duplication and recruitment only works if very few changes are required to acquire novel selectable utility or neo-functionalization. If a duplicated gene is neutral (in terms of its cost to the organism), then the maximum number of mutations that a novel innovation in a bacterial population can require is up to six. If the duplicated gene has a slightly negative fitness cost, the maximum number drops to two or fewer (not inclusive of the duplication itself).
It seems that the bacterial flagellum is as much a — and perhaps a greater — challenge to Darwinism as it was when Behe first wrote Darwin’s Black Box in 1996.
I am hoping that Jonathan will be able to pursue his studies in graduate school.
Filed under: News, Bacteria, Bacterial Flagellum, Binding Site, Darwinian Evolution, Darwinism, Design, E.Coli, Evolution, Flagellum, Host, Immune System, Intelligent Design, Irreducible COmplexity, Michael Behe, Mike Behe, Parasite, Protein, Protein Folding, Salmonella, Type III Secretory System, Yersinia, Yop Cannon