Braterman: Moving Goal Posts on Irreducible Complexity


(S. Joshua Swamidass) #1

A useful explanation I just found of how moving goal posts work with irreducible complexity comes from this review of Behe’s 2010 review of the literature: Behe’s review in context, or what’s the point?.

Behe constructs an elaborate apparatus for classifying mutations as “gain”, “modification”, or “loss” of what he calls a Functional Coded Element (FCT). The definition is skewed to make “gain” as difficult to prove as possible. The process needs to be understood at the molecular level, rather than simply in terms of phenotype expression. This enables him to dismiss as of unproven relevance the Lenski group’s famous demonstration of E.Coli acquiring the ability to metabolise citrate under anaerobic conditions. Moreover, advantageous removal of inhibition is treated as “loss”, but advantageous disruption of a function by IS duplication and insertion is classified as “modification”, rather than “gain”. Using these restrictive and asymmetric criteria, Behe classifies most sufficiently well-understood mutations in laboratory-bred bacteria as loss or modification, although he does recognise a few gains.

But there are numerous well-known counterexamples, many of them discussed in this review.

The next stage is rhetorical dismissal of such counterexamples. Here the strategies include limiting the search (ignoring the massive creative role of gene duplication and polyploidy in eukaryotes, and of horizontal transfer followed by selection in bacteria themselves), narrowing the criteria (new functions don’t count unless they can be demonstrated to arise from additions, rather than any other kinds of alterations, to the molecular machinery), and inventing additional constraints (creation of a new category, the FCT, classifying the process as a loss if either material or function is lost at any stage in the change being discussed, dismissing changes in function as mere transformations, rather than novelties). This stage switches the emphasis from what is possible in principle, to the demand that each case be demonstrated in practice, and fully analysed in detail, at the molecular level.

Finally, any counterexamples still surviving this moving of the goalposts and restricting and tilting of the playing field are dismissed as untypical, and therefore unimportant. Another leap of logic, as the present case shows. For even if losses (according to Behe’s criteria) outnumber gains, losses are in general unlikely to be dramatic without being lethal—there are some obvious well-known exceptions, such as the evolution of parasitism—whereas dramatic gains such as gene duplication, horizontal gene transfer, or polyploidy, can and do have the most profound effects imaginable.

You can read Behe’s paper here:

Lents and Swamidass: Our Questions for Behe’s Darwin Devolves
The Stone Bridge example and IC
(S. Joshua Swamidass) #2

I also find it surprising and striking that Behe does not even mention the Muller Two-Step, a well known process for evolving IC: Which Irreducible Complexity Argument?

(S. Joshua Swamidass) #3

Another set of excellent quotes from an article that was published alongside Behe’s.

Irreducible Incoherence and Intelligent Design: A Look into the Conceptual Toolbox of a Pseudoscience.

In his initial definition, Behe seems to intend the weak interpretation, but he then proceeds to use the concept in a line of reasoning that only makes sense under the strong interpretation. Precisely because the bacterial flagellum is IC, Behe tells us, it could not have evolved by means of random mutation and natural selection. However, when critics object that the system’s components may well be able to perform other functions in other contexts, or when they point to the possibility of indirect evolutionary pathways, Behe switches back to the weak definition and blames his critics for misrepresenting his argument.

Not, how this author also sees the switching between definitions in IC. The “weak” and “strong” versions correspond to IC1 and IC2, in the parlance we have used here. IC1 is very easy too measure, but IC2 is nearly impossible to measure.

This allows for an interesting bait-and-switch strategy, which one could describe as follows: ‘First present evidence for weak IC in the living world, then pretend that strong IC has been demonstrated and continue to equate IC with “unevolvability”. If challenged on empirical grounds, jump back to the weak version and accuse your critics of misrepresenting your argument. Switch the IC claim to subsystems and assembly of components, keep raising the standards of evidence, and reassert that all this directly follows from the simple objective criterion of IC. Finally, when really pressed against the wall, give up this particular system and quickly find a new one. Repeat the circle ad libitum.’ Further equivocations

In any case, what is disingenuous in Behe’s presentation is that this challenge to offer a complete and step-by-step evolutionary account of IC systems is not spelled out from the beginning, but is a belated revision of his original claim (based on ambiguities in his definition). In Darwin’s black box, Behe leaves us with the impression that the concept of IC is in principle easy to challenge, but when his critics actually set out to do so, as we saw in the discussion with Pennock and Miller, Behe dodges and weaves like a hunted rabbit.

Behe’s claim has indeed been tested against the facts and found wanting (Miller, 2000; Lenski et al., 2003; Young and Edis, 2006; Forrest and Gross, 2007a). In response to these demonstrations, however, IDC proponents belatedly ‘reinterpret’ their initial claims in order to lift them out of the critic’s reach. A first strategy to this end consists in shifting the burden of proof from plausible evolutionary pathways to the actual evolutionary story, maintaining that the broad outlines of a plausible evolutionary account amounts to nothing more than Darwinian wishful thinking and speculation. The same bait-and-switch technique can be discerned here: IC is constantly boasted as a point of principle for ruling out the possibility of evolutionary explanations, but as soon as it is challenged on that ground, through a discussion of plausible evolutionary scenarios, ID creationists pretend that they were talking about actual evolutionary pathways all along.

This is an important point too, that came up just yesterday. The IC argument is merely a logical argument about plausibility, but when plausible pathways are supposed, there is a shift to demand evidence for what actually happened. This creates a large asymmetry in the argument, where a logical argument about implausibility does not tolerate a logical argument that demonstrates it is wrong. This dismissal is merely on the grounds that it is not empirically demonstrated, no matter the fact that it shows logical errors in the original argument it is disputing.

Lents and Swamidass: Our Questions for Behe’s Darwin Devolves
Prof. Behe's debate with Prof. Moran
The Stone Bridge example and IC
(Dan Eastwood) #4

Braterman is always a good read. Maybe if we keep sharing his article we can lure him here. :slight_smile:


“Spetnerian metrics” at play again. :crazy_face:

(George) #6

How can we see the rise of tetrapods as evolution … when we know it leads to a tragic loss of gills! Oh the sorrow of walking around on dry land without a full set of moisture-gushing gills!

(S. Joshua Swamidass) #7

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