Comments on Buggs: TSS and the Flagellum

What’s the problem? An IC system S can comprised several IC subsystems A, B etc…In that case, there is no theoretical barrier to the idea that say subsystem A’ may have devolved from S. Such scenario doesn’t the least refute ID.

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Well it does refute the idea that S couldn’t have evolved because reduced versions of it are by definition nonfunctional.

The claim originally (Behe 1996, Darwin’s Black Box) that Kenneth Miller was addressing, is that an IC system can’t evolve since by definition any system that lacks parts is nonfunctional.

“An irreducibly complex system cannot be produced directly by numerous, successive, slight modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. … Since natural selection can only choose systems that are already working, then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on.” (Behe 1996b)

My bold.

In response to the successful rebuttals to this definition (that intermediate stages might have other functions, instead of selection for that final one function driving the gradual elaboration of the system), Behe changed it. That suggests Behe implicitly agreed his original definition of IC had a major weakness, which he then later tried to address.

If a system S has IC subsystems A and B, then system S by Behe’s 1996 definition isn’t actually IC, since S can lack parts (such as part A, leaving only part B) yet remain functional. That implies there’s a way to get from simpler systems A or B to more complex system S while retaining a functional system. If you can evolutionarily reduce a complex system step by step, while still retaining a functional structure, why can’t you reverse that order of events?


a sub part of a watch with a compass can also be functional by itself (the compass). but it doesnt mean there are small steps from a compass to a watch with a compass. thus, the flagellum cant realy evolve from the TTSS or vice versa.

No, it doesn’t, for the argument from IC states that an IC system S with function F couldn’t have evolved because reduced versions of it are by definition nonfunctional with respect to function F.

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That’s not what Behe wrote in 1996, as quoted above.

But more importantly, your modification of the definition is equally vulnerable to the exact same rebuttal. Subsystem Ss(T3SS) of S(flagellum) might lack function F (propulsion for flagella), but instead have subfunction Fs(protein secretion). So while system S might be IC with respect to F (removing a part results in loss of function F) does not necessarily result in a nonfunctional system.

This whole debate has been had already. Behe abandoned the original definition for a good reason. It’s why he started waving his hands in the direction of “each additional step becomes more improbable” to try to save his IC concept instead. The concept has gone through multiple iterations since it’s inception in response to criticisms. If the original concept really stood up to all these responses there’d be no reason for Behe to update it. But he did. We can see why. It’s ridiculously easy to to show that it has major flaws in it, both logically and with concrete examples.

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That is a logically invalid claim.

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You have to be careful with things that are true by definition. In this case one of Behe’s major problems is that he assumes a system must evolve (in his strawman scenario that he thinks can’t happen) by the sequential addition of invariant parts. But evolution just doesn’t work that way. Parts can be added and subtracted, and they can change while they’re in place. What was non-essential can become essential, and what was essential can become non-essential.


Sure, but so what? If a system S with a specific function F is IC, it is with respect to this specific function F, not with respect to some other function, be it or not a function of some subsystem of S.

So what? So then the appeal to IC becomes meaningless as an attempt to undermine evolution, since clearly evolution does not require that some structure maintains the one same function throughout it’s evolution.


Where did you get this idea that Behe assumes a system must evolve by the sequential addition of invariant parts? Do you have a reference supporting this claim?

can you make a watch by functional small steps by using any such process?

Even if true, I don’t see how your claim above refutes the IC argument.

Watches did not arise thru evolution.

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Uhm, okay. Then I think you have problems that extend beyond biology. I can live with that.


Yes, thanks to the invention of the mainspring in the 15th century.

The Evolution Of The Watch
From pocket accessories to digital wrist

how many parts require a minimal clock?

I don’t know but there are many more parts to a simple watch than the three structural elements of a flagellum so any analogy between them is weak.

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Only every example of IC he’s ever presented.

a tipical flagellum contain about 30 different proteins, which is very similar to a watch:

(image from Names of movement parts - Chat About Watches & The Industry Here - Watch Repair Talk)

so the analogy is great.

A typical watch contains zero proteins, unless you try to repair it with butter. But that doesn’t work, even if you use the best butter.