Michael Behe Hasn’t Been Refuted on the Flagellum
by Jonathan M
Those of us who have been reading the literature surrounding the ID/evolution controversy for any length of time will be quite acquainted with the standard Darwinian retort with regards the “Behean” argument for irreducible complexity as far as the bacterial flagellum is concerned. There seems to be this unanimity of opinion among Darwinian theorists that the claims of irreducible complexity with respect to the bacterial flagellum have been refuted, and that we ID proponents are constantly shifting the goal posts, burying our heads in the sand, and generally clutching at straws. Indeed, one person on Facebook recently remarked,
My main gripe with the ID proponents is that they never seem to give up. How many times do you need to be told that something is wrong before you’ll admit it? How many times does ID need to be refuted in the peer reviewed media before you’ll give it up as a lost cause? The bacterial flagellum irreducible complexity story is completely and utterly dead. It’s wrong. Get over it.
I recently brought up the flagellum, as a documented instance of irreducible complexity, at a lunch bar Q&A session on the science/faith intersect, and received responses to much the same effect.
But is this claim actually true? Has this argument been refuted by critics? 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…
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