Wednesday, February 18, 2009

Intelligent Design - Irreducible Complexity

The other main argument used by Intelligent Design advocates is called “irreducible complexity”. The person who came up with that phrase is Dr. Michael Behe. Dr. Behe is a professor of biochemistry at Lehigh University in Pennsylvania. He is also the author of a book titled “Darwin’s Black Box” that was published in 1996.

In his book, Behe claims that there are many genetic “designs” in various organisms that require many individual components to all be working correctly. That could not happen through evolution because evolution requires the gradual accumulation of components rather than the sudden appearance of many components that work together perfectly at one time.

The analogy he uses is to a mousetrap. If you remove any component used in the mousetrap – the wooden base, the spring, the stick, the hammer, etc. – the mousetrap is ineffectual. Therefore the mousetrap is “irreducibly complex”.

Behe then claims that there are organisms with “designs” which are also irreducibly complex. He cites the blood clotting system in mammals and the flagellum of the bacteria as primary examples.

Behe is correct when he says that evolution could not come up with a mechanism that explains irreducible complexity. However there are flaws in his argument when applied to his examples.

In general, his examples require a level of technical detail that is beyond the intended scope of this book. (Even in his book “Darwin’s Black Box”, Behe highlights his more technical discussions and warns the readers that they may not understand those sections.) However, other biochemists who do understand his examples claim to have shown that Behe’s arguments of “irreducible complexity” are wrong and that there are very reasonable pathways for those things to have evolved gradually, step-by-step, as evolution requires. For example, the biochemist Dr. Kenneth Miller dedicates a chapter in his book “Finding Darwin’s God” to specifically refuting Behe’s claims. Dr. Miller and others point out how there are blood clotting mechanisms that work quite well without all of the components that Behe insists are necessary and also how the flagellum of the bacteria is very similar to non-flagella in other bacteria. People have even described examples of how a mousetrap could evolve through a gradual set of steps[1].

At a common-sense level, there are two fundamental problems with his arguments.

First, he is really just using the “God of the Gaps” argument. He claims that if he doesn’t personally understand how some particular feature could have evolved then there is no possible explanation for how it could have evolved. As became obvious during his testimony in a Dover, Pennsylvania, court case regarding intelligent design, Behe is unwilling to consider evidence, even when published in scientific papers, that contradicts his claims that some things are irreducibly complex. If he were more honest, he would concede that it is impossible to “prove” a negative claim and that his examples may have evolutionary paths that he simply doesn’t understand.

Second, Behe insists that evolution only works through the accumulation of “components”. In fact, it sometimes works through the deletion of “components”.

A vivid example of this can be found at the talkorigins web page at On that web page Dr. Douglas L. Theobald, a biochemist at Brandeis University uses the example of a stone bridge, as shown below, to show how something can evolve through the deletion of components to appear as if it were irreducibly complex.
[1] See for example.

If someone was to look at this bridge completely independently of anything else, they would say that it is irreducibly complex. If you remove any of the components, the bridge won’t work.

But the original bridge may have looked quite different. For example, it could have looked like this:

There is a perfectly functional bridge made up of individual components. Those components could have been added one-at-a-time. If, for example, the bridge crossed over a stream the individual stones might have been added one-at-a-time as the stream widened.

Then at a later time, another – basically redundant component – was added such that the bridge looked like this:

Note that we can provide an explanation for how each and every one of these components was added incrementally. We still have a perfectly functioning bridge.

It’s now apparent that the middle foundation stone could be removed with no loss of functionality resulting in the apparently “irreducibly complex” bridge with which we started.

And, in fact, we see many cases where there are redundant genes in organisms[1]. Therefore such a proposed hypothesis could be applied to living organisms without any problems. Note that DNA and genes don’t fossilize. So there is no way of confirming how any particular set of genetic characteristics came into existence at the micro-biological level. But every example that Behe or other ID advocates use can be easily explained by such mechanisms[2].

The bottom line: Behe cannot claim that he has falsified evolution with his examples of irreducible complexity.

Another important point is that ID is not scientific. It cannot be falsified.

A creationist that I have debated said this:

> ...some say that ID has no predictive value. Of course
> they have already rejected, with a wave of the hand,
> the significance of finding irreducibly complex structures
> ones that cannot be made by adding pieces one at a
> time. Yet living things are full of them.

Effectively the argument that we see here is that ID makes testable predictions. The problem is that these are not potentially falsifiable predictions.
We’ve already discussed irreducible complexity and seen that it can’t be proven to exist. We have also discussed how in the last few centuries, a hypothesis must be falsifiable in order to be considered scientific. (There must be some possible piece of evidence which, if found, would show that the hypothesis is false.) But the real point of emphasis is this: if, hypothetically, all of those supposed examples of irreducible complexity were found to have evolutionary explanations, would ID have been falsified? Would everyone who supported ID be forced to give up that hypothesis?

Of course not! The ID advocates would simply shrug and move on to find other “evidence” supporting their claims. None of them would concede a single piece of evidence which, if found, would falsify ID once and for all.

Therefore, because ID is not falsifiable, it is not science.

That’s a very good reason for believing that it should not be taught in science classrooms.

[1] See for example (referenced on February 2, 2009). A Google search for “redundant genes” resulted in an estimated 2 million hits.
[2] It is worth noting that in his most recent book titled “The Edge of Evolution” Behe finds a few other examples of irreducible complexity that many theistic people would find offensive. For example, he clams that the disease malaria is the result of an intelligent designer because it is irreducibly complex. In other words, Behe’s designer has quite a malicious streak.

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