EvC Forum: How do we know its irreducible?

This is following on from a previous thread in which myself an Ahmad are discussing Behe's notion of irreducible complexity.

My attempted "impartial" summary of the discussion goes like:

I try to assert that to demonstrate IC, and hence falsify evolution, one must show that it is impossible for apparent IC systems to have come about through evolutionary processes.
Ahmad maintains that the burden of proof is on science to demonstrate how IC systems came about through gradual processes. He's also given me a few examples of what he considers to be IC systems (bombardier beetles, cillia) as well as briefly mentioning a few others. (Ahmad - hope this is fair

)

Ahmad,

Lets backtrack to my original post to you:

I said:

quote:
Consider the following statements:

1) it is demonstrably impossible for X to produce Y
2) I cannot see how X could produce Y
3) it is conceivable that X has produced Y, but the process has not been determined yet.
4) X has been conclusively shown to produce Y

Now I would paraphrase your position as being (2), wheras your standard biologist would argue (3) (or (4)!) when it comes to irreducibly complex systems.

To overturn a pardigm, you generally have to do more than insist upon (2), you have to show that (1) must be the case.

To which you responded:

quote:
Secondly, (1) is exactly the case here. According to ToE, systems have evolved from simple to complex by natural selection and random mutations gradually but sometimes in irregular leaps (punctuated equilibria). If that is the case with a system, it is not irreducibly complex; in fact, it CANNOT be irreducibly complex since it evolved according to Behe's defintion. An IC system needs all its parts to effectively function such as if, even, one of the parts is missing, the system will cease to function. Therefore, an IC system, by definition, is unevolvable... unless proven otherwise. Surely, if a system is IC, it must have had ALL its parts from the very beginning of its existence (aka creation).

Firstly, lets just simplify definitions just for the purpose of this argument, to avoid confusion. I know it doesn't quite meet with Behe's definition, but lets just say that an IC system is one that cannot have come about through gradual change, which I think is the same as what you were getting at above. The challenge for us is to then to determine whether or not IC systems exist.

To do this, you have to show that it is impossible for the system to have arisen through gradual change. If I cannot provide an evolutionary pathway, then we have only succeeded in showing at most (2)I cannot see how X could produce Y, which is no falsification of evolution. Would you agree?

Now, there are many possible routes to get from X to Y, via Z for example. Any claims of impossibility must also take different routes into account, as long as the time periods involved are not too great.

If we then look closer at your cillia example, I'm looking here for the point at which you declare that for it to be brought about by gradual change is impossible.

quote:
For without one of these components, the system simply will not function. We can't evolve a cilium by starting with microtubules alone, because the microtubules will be fixed and rigid-not much good for moving around. Adding the flexible linker bridges to the system will not do any good either-there is still no motor and the cilia still will not bend. If we have microtubules and the walker arms (the motors) but no flexible linker arms, the microtubules will keep on sliding past each other till they float away from each other and are lost.

The first thing I note about this is that you are (implicitly) claiming that each separate component does not have a function in its own right. If you are claiming this, this is a pretty bold claim. If not then I don't see how you can claim IC.

It doesn't seem to me that you've considered all potential pathways here. Its pretty obvious that you haven't. Could the organism have evolved features which became redundant and then evolved into apparent IC? You don't discuss this. Until you do, its still an argument from incredulity I'm afraid.

quote:
All consist of a very complex system of interacting parts which cannot be simplified while maintaining functionality

Does Behe give a mousetrap as an example of an IC system as well?

quote:
Evolution simply cannot produce complex structures in a single generation as would be required for the formation of irreducibly complex systems

You haven't demonstrated this. You simply believe it.

quote:
To imagine that a chance set of mutations would produce all 200 proteins required for cilia function in a single generation stretches the imagination beyond the breaking point

Agreed. If this is what you believe the naturalistic explanation of the cilia's evolution to be then no wonder you are incredulous.

quote:
And yet, producing one or a few of these proteins at a time, in standard Darwinian fashion, would convey no survival advantage because those few proteins would have no function

Its that word "function" again. By function, do you mean "selective advantage"? How do YOU know what confers selective advantage?

To help you out, this paper discusses the potential routes Darwinian evolution can take. I'll list them out here:

Serial direct Darwinian evolution
Parallel direct Darwinian evolution
Elimination of functional redundancy
Adoption from a different function (joining of two or more non-irreducibly complex structures of functionally indivisible components or supply of an existing irreducibly complex structure of functionally indivisible components

You have to show how any structure you claim (note: positive claim) to be IC cannot have arisen through any of the means above. Thats why I can't see how you'd do it.

PS This wasn't going to be in the thrust of my argument so grateful if you'd treat as an aside (maybe respond separately):

About Isaak on bombardier beetles:

quote:
He fails to mention the step-by-step evolution of the inhibitor and anti-inhibitor that the beetle possesses without which it will blow itself up to an oblivion!!

Which inhibitors / anti-inhibitors? Why do you think that without these the beetle would blow itself up?

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It's good to have an open mind, but not so open that your brains
fall out. - Bertrand Russell

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