More Irreducible Complexity Is Found in Flagellar Assembly


If a structure is irreducibly complex, the assembly instructions are often even more irreducibly complex. Case in point: the bacterial flagellum.

When mainstream science journals corroborate claims we've made in support of the theory of intelligent design, we like to point it out. It shows that the case for ID grows stronger, not weaker, with time. Eleven years ago in the Illustra film Unlocking the Mystery of Life, Scott Minnich said that the assembly instructions for building a flagellum are even more irreducibly complex than the outboard-motor-like structure itself. He was right; a new paper in PNAS, with dazzling illustrations, opens Darwin's black box a little more, showing the amazing sequential assembly of this icon of ID.

The 12 authors from 5 American universities don't seem to have much use for evolutionary theory. They never mention it. Instead, they call the flagellum a "sophisticated self-assembling molecular machine" and, twice, "an intricate molecular machine."

The organism they studied is the multi-flagellated spirochete that causes Lyme disease -- but that's a side issue for philosophers or theologians, not for intelligent design. ID looks for products that imply intelligent causes, not for the reasons they exist.

The abstract gives a quick summary of their findings:

In this study, we genetically trapped intermediates in flagellar assembly and determined the 3D structures of the intermediates to 4-nm resolution by cryoelectron tomography. We provide structural evidence that secretion of rod substrates triggers remodeling of the central channel in the flagellar secretion apparatus from a closed to an open conformation. This open channel then serves as both a gateway and a template for flagellar rod assembly. The individual proteins assemble sequentially to form a modular rod. The hook cap initiates hook assembly on completion of the rod, and the filament cap facilitates filament assembly after formation of the mature hook. (Emphasis added.)

So already we see confirmation of the sequential nature of construction, just like Minnich described in the film:

[Minnich] Even if you concede you had all the parts necessary to build one of these machines, that's only part of the problem. Maybe even more complex -- I think more complex -- is the assembly instructions. That is never addressed by opponents of the irreducible complexity argument.

[Narrator] Studies of the bacterial motor have, indeed, an even deeper level of complexity. For its construction not only requires specific parts, but also a precise sequence of instructions for assembly.

[Minnich] You've got to make things at the right time. You've got to make the right number of components. You've got to assemble them in a sequential manner. You've got to be able to tell if you've assembled it properly so that you don't waste energy building a structure that's not going to be functional....

You build this structure from the inside out. You're counting the number of components in a ring structure or the stator, and once that's assembled, there's feedback that says, "OK, no more of that"; now, a rod is added; a ring is added; another rod is added; the U-joint [hook] is added. Once the U-joint is add a certain size, and a certain degree of bend, about a quarter turn, that's shut off, and then you start adding components for the propeller. These are all made in a precise sequence, just like you would build a building.

Paul Nelson then elaborates that the construction of one irreducibly complex machine (like the flagellum) requires the work of other machines; and those machines require other machines for their assembly. The whole assembly apparatus is itself irreducibly complex. In a memorable line, Jonathan Wells says, "what we have here is irreducible complexity all the way down."

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