Mousetrap without bait isolate on a black background. Stock photo traps.

Irreducible Complexity is an Obstacle to Darwinism Even if Parts of a System have other Functions

A Response to Sharon Begley's Wall Street Journal Column

In a recent column in the Wall Street Journal (February 13, 2004, Science Journal, page B1, “Evolution Critics Come Under Fire for Flaws In ‘Intelligent Design'”) science writer Sharon Begley repeated some false claims about the concept of irreducible complexity (IC) that have been made by Darwinists, in particular by Kenneth Miller, a professor of biology at Brown University. After giving a serviceable description in her column of why I argue that a mousetrap is IC, Begley added the Darwinist poison pill to the concept. The key misleading assertion in the article is the following: “Moreover, the individual parts of complex structures supposedly serve no function.” In other words, opponents of design want to assert that if the individual parts of a putatively IC structure can be used for anything at all other than their role in the system under consideration, then the system itself is not IC. So, for example, Kenneth Miller has seriously argued that a part of a mousetrap could be used as a paperweight, so not even a mousetrap is IC. Now, anything that has mass could be used as a paperweight. Thus by Miller’s tendentious reasoning any part of any system at all has a separate “function”. Presto! There is no such thing as irreducible complexity.

That’s what often happens when people who are adamantly opposed to an idea publicize their own definitions of its key terms — the terms are manipulated to wage a PR battle. The evident purpose of Miller and others is to make the concept of IC so brittle that it easily crumbles. However, they are building a straw man. I never wrote that individual parts of an IC system couldn’t be used for any other purpose. (That would be silly — who would ever claim that a part of a mousetrap couldn’t be used as a paperweight, or a decoration, or a blunt weapon?) Quite the opposite, I clearly wrote in Darwin’s Black Box that even if the individual parts had their own functions, that still does not account for the irreducible complexity of the system. In fact, it would most likely exacerbate the problem, as I stated when considering whether parts lying around a garage could be used to make a mousetrap without intelligent intervention.

In order to catch a mouse, a mousetrap needs a platform, spring, hammer, holding bar, and catch. Now, suppose you wanted to make a mousetrap. In your garage you might have a piece of wood from an old Popsicle stick (for the platform), a spring from an old wind-up clock, a piece of metal (for the hammer) in the form of a crowbar, a darning needle for the holding bar, and a bottle cap that you fancy to use as a catch. But these pieces, even though they have some vague similarity to the pieces of a working mousetrap, in fact are not matched to each other and couldn’t form a functioning mousetrap without extensive modification. All the while the modification was going on, they would be unable to work as a mousetrap. The fact that they were used in other roles (as a crowbar, in a clock, etc.) does not help them to be part of a mousetrap. As a matter of fact, their previous functions make them ill-suited for virtually any new role as part of a complex system.

Darwin’s Black Box, page 66.

The reason why a separate function for the individual parts does not solve the problem of IC is because IC is concerned with the function of the system:

By irreducibly complex I mean a single system which is composed of several well-matched, interacting parts that contribute to the basic function, and where the removal of any one of the parts causes the system to effectively cease functioning.

Darwin’s Black Box, page 39.

The system can have its own function, different from any of the parts. Any individual function of a part does not explain the separate function of the system.

Miller applies his crackerjack reasoning not only to the mousetrap, but also to the bacterial flagellum — the extremely sophisticated, ultra complex biological outboard motor that bacteria use to swim, which I had discussed in Darwin’s Black Box and which has becoming something of a poster child for intelligent design. No wonder, since anyone looking at a drawing of the flagellum immediately apprehends the design. Since the flagellum is such an embarrassment to the Darwinian project, Miller tries to distract attention from its manifest design by pointing out that parts of the structure can have functions other than propulsion. In particular, some parts of the flagellum act as a protein pump, allowing the flagellum to aid in its own construction — a level of complexity that was unsuspected until relatively recently.

Miller’s argument is that since a subset of the proteins of the flagellum can have a function of their own, then the flagellum is not IC and Darwinian evolution could produce it. That’s it! He doesn’t show how natural selection could do so; he doesn’t cite experiments showing that such a thing is possible; he doesn’t give a theoretical model. He just points to the greater-than-expected complexity of the flagellum (which Darwinists did not predict or expect) and declares that Darwinian processes could produce it. This is clearly not a fellow who wants to look into the topic too closely.

In fact, the function of a pump has essentially nothing to do with the function of the system to act as a rotary propulsion device, anymore than the ability of parts of a mousetrap to act as paperweights has to do with the trap function. And the existence of the ability to pump proteins tells us nil about how the rotary propulsion function might come to be in a Darwinian fashion. For example, suppose that the same parts of the flagellum that were unexpectedly discovered to act as a protein pump were instead unexpectedly discovered to be, say, a chemical factory for synthesizing membrane lipids. Would that alternative discovery affect Kenneth Miller’s reasoning at all? Not in the least. His reasoning would still be simply that a part of the flagellum had a separate function. But how would a lipid-making factory explain rotary propulsion? In the same way that protein pumping explains it — it doesn’t explain it at all.

The irreducible complexity of the flagellum remains unaltered and unexplained by any unintelligent process, despite Darwinian smoke-blowing and obscurantism.

I have pointed all this out to Ken Miller on several occasions, most recently at a debate in 2002 at the American Museum of Natural History. But he has not modified his story at all.

As much as some Darwinists might wish, there is no quick fix solution to the problem of irreducible complexity. If they want to show their theory can account for it (good luck!), then they’ll have to do so by relevant experiments and detailed model building — not by wordplay and sleight-of-hand.

Michael J. Behe

Senior Fellow, Center for Science and Culture
Michael J. Behe is Professor of Biological Sciences at Lehigh University in Pennsylvania and a Senior Fellow at Discovery Institute’s Center for Science and Culture. He received his Ph.D. in Biochemistry from the University of Pennsylvania in 1978. Behe's current research involves delineation of design and natural selection in protein structures. In his career he has authored over 40 technical papers and three books, Darwin Devolves: The New Science About DNA that Challenges Evolution, Darwin’s Black Box: The Biochemical Challenge to Evolution, and The Edge of Evolution: The Search for the Limits of Darwinism, which argue that living system at the molecular level are best explained as being the result of deliberate intelligent design.