A Torley Defense of Irreducible Complexity

Vincent Joseph Torley (vjtorley) has a Ph.D. in Philosophy (2007) from the University of Melbourne (Australia). He currently teaches English in Japan.

Torley hangs out at Uncommon Descent where he tries to defend Intelligent Design Creationism. He didn't like my recent posting on Irreducible Complexity [Barry Arrington Explains Irreducible Complexity] because I accused Barry Arrington of not understanding evolution. You might recall that Arrington began his defense of irreducible complexity by saying, "(1) By definition, evolution can work only in a stepwise fashion wherein each successive step is “selected for” because it has conferred a selective advantage on the organism."

This is not how evolution is defined and it's a particularly bad way to begin because the scientific understanding of many irreducibly complex systems involves the fixation of neutral or even detrimental alleles. Competency in evolution also requires an understanding of redundancy, contingency, and sloppiness.

Vincent Joseph Torley asks, "Will this do, Professor Moran?" He starts with ....

Let me state up-front that I am a philosopher, not a scientist. However, I believe in arguing rigorously, so I have attempted to state the argument from irreducible complexity in a rigorous fashion. I’d appreciate hearing from Professor Moran thinks of this argument, as a biologist.

Hmmm .... this seems like a pretty damning confession when your goal is to show that IDiots understand evolution well enough to know when it's impossible. I accused Barry Arrington of screwing up his defense of irreducible complexity because he started with an incorrect assumption about evolution. Now Torley weighs in with an up front confession that he, too, lacks expertise in the very subject he is criticizing. Doesn't anyone else find this a bit bizarre?

Here's the version of irreducible complexity that Vincent Joseph Torley is defending. It comes from William Dembski (not a biochemist) at Irreducible Complexity Revisited (2004).

The basic logic of IC [Irreducible Complexity] goes like this:

A functional system is irreducibly complex if it contains a multipart subsystem (i.e., a set of two or more interrelated parts) that cannot be simplified without destroying the system’s basic function. I refer to this multipart subsystem as the system’s irreducible core.

We can therefore define the core of a functionally integrated system as those parts that are indispensable to the system’s basic function: remove parts of the core, and you can’t recover the system’s basic function from the other remaining parts. To say that a core is irreducible is then to say that no other systems with substantially simpler cores can perform the system’s basic function.

It's important to keep this definition in mind because later on we'll see how Michael Behe changes the definition in light of biochemical facts.

Torely goes on to list several possible ways by which an irreducibly complex system could evolve by "unguided, Darwinian evolution." He then "proves" that none of them could work without ever discussing a single biological example.

I'm especially interested in his 4th example ...

(iv)(a) adds a new part to / alters an old part in an existing system with function G, thereby generating a system which is able to perform a brand new function F; {co-option} and/or {transformation}

...

Why (iv)(a) won’t work

However, it’s very unlikely that a system with function G, which gains one new part, while keeping the existing parts in nearly the same configuration as they were before, should suddenly be able to perform a totally new function F, especially if the number of parts in the system is large. Reason: the space of all possible configurations is astronomically large. However, the vast majority of configurations don’t do anything useful: they have no functionality. (Think of amino acid chains.) The number of possible functions is therefore much, much smaller than the number of possible configurations, and different functions are likely to be isolated on little islands of configuration space. If just adding one part to a complex system with an existing function G were enough to generate a system with a new function F, that would mean, contrary to supposition, that the two functions were relatively close together in configuration space. As the number of parts n of the complex system increases, however, this scenario becomes less and less plausible. (And now think of Behe’s bacterial flagellum. Even the simplest flagella require 30 parts. The idea that adding one part to an existing 29-part system would somehow magically confer the functionality of the flagellum appears to be extremely unlikely.)

But this is exactly how the irreducibly complex citric acid cycle arose! Most species of bacteria have a forked pathway for synthesis of organic acids. One of the forks, the oxidative pathway, leads to the synthesis of α-ketoglutarate from citrate and acetyl-CoA. α-Ketoglutarate is an important precursor for amino acid biosynthesis. The other pathway, the reductive pathway, leads to the synthesis of succinyl-CoA, a precursor of heme-like molecules. These species do not have a citric acid cycle.

Some bacteria have an additional enzyme, called α-ketoglutarate dehydrogenase, that converts α-ketoglutarate to succinyl-CoA thus forming a circular pathway by reversing the reductive pathway to create a way of oxidizing acetyl CoA and producing high energy molecules. Note that in the new circular pathway, a two-carbon molecule (acetyl group) is completely oxidized to two molecules of CO₂ and the initial substrate (oxaloacetate) is regenerated. If you remove any of the enzymes in this pathway you break the circle and lose the ability to oxidize acetate.

The important points are that the citric acid cycle is an excellent example of an irreducibly complex system according to Dembski's definition and that it arose in a single step from two other pathways that had different functions.

THEME:
Pyruvate
Dehydrogenase
The new enzyme, α-ketoglutarate dehydrogenase, carries out a very similar reaction to another important enzyme called pyruvate dehydrogenase and it's very clear that the new citric acid cycle enzyme evolved from pyruvate dehydrogenase [Pyruvate Dehydrogenase Evolution].

None of the other "proofs" that Torley offers are any better. It's quite easy to think of examples that correspond to the steps that Torley says are impossible.

Michael Behe is a biochemist. He knows about most of these examples and that's why his definition of irreducible complexity is tweaked in order to eliminate metabolic pathways like the citric acid cycle. Neither Torley nor Arrington (nor Dembski) are aware of these problems so they try to defend a version of irreducible complexity that Behe rejects. Here's what Behe says in Irreducible Complexity and the Evolutionary Literature: Response to Critics.

Finally [KEN LAM] Miller discusses a paper which works out a scheme for how the organic-chemical components of the tricarboxylic acid (TCA) cycle, a central metabolic pathway, may have arisen gradually. (Melendez-Hevia et al. 1996) There are several points to make about it. First, the paper deals with the chemical interconversion of organic molecules, not the enzymes of the pathway or their regulation. As an analogy, suppose someone described how petroleum is refined step by step, beginning with crude oil, passing through intermediate grades, and ending with, say, gasoline. He shows that the chemistry of the processes is smooth and continuous, yet says nothing about the actual machinery of the refinery or its regulation, nothing about valves or switches. Clearly that is inadequate to show refining of petroleum developed step by step. Analogously, someone who is seriously interested in showing that a metabolic pathway could evolve by Darwinian means has to deal with the enzymic machinery and its regulation.

The second and more important point is that, while the paper is very interesting, it doesn't address irreducible complexity. Either Miller hasn't read what I said in my book about metabolic pathways, or he is deliberately ignoring it. I clearly stated in Darwin's Black Box metabolic pathways are not irreducibly complex (Behe 1996) (pp. 141-142; 150-151), because components can be gradually added to a previous pathway. Thus metabolic pathways simply aren't in the same category as the blood clotting cascade or the bacterial flagellum. Although Miller somehow misses the distinction, other scientists do not. In a recent paper Thornhill and Ussery write that something they call serial-direct-Darwinian-evolution "cannot generate irreducibly complex structures." But they think it may be able to generate a reducible structure, "such as the TCA cycle (Behe, 1996 a, b)." (Thornhill and Ussery 2000) In other words Thornhill and Ussery acknowledge the TCA cycle is not irreducibly complex, as I wrote in my book. Miller seems unable or unwilling to grasp that point.

Let me clarify Behe's point. The citric acid cycle is irreducibly complex by most of the definitions offered by Intelligent Design Creationists. However, Michael Behe—the only biochemist on the team—says that pathways like the citric acid cycle can't be irreducibly complex because it's too easy to see how they could evolve in a stepwise manner.

I wish the IDiots would get their acts together because it would be a lot easier to refute them all at once instead of having to deal with several different versions of each attack on evolution. Let me help out by giving them the latest version of irreducible complexity that takes real science into account.

An irreducibly complex system is a complex system where every part is needed for its function. An irreducibly complex system cannot be produced by any known evolutionary mechanism because as soon as such an explanation becomes available the complex is, by definition, no longer irreducibly complex.

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