by Lenny Flank
(c) copyright 2006
The most widely-known proponent of the "irreducible complexity" argument has been Michael Behe, a Roman Catholic who, unlike most creationists, accepts that life evolved over billions of years and also accepts that humans are evolved from apelike primates, but who thinks that God (uh, I mean "an Unknown Intelligent Designer") intervenes at certain points to manipulate the evolutionary process. In his book Darwin's Black Box, Behe uses a concept he calls "irreducible complexity" to illustrate this intervention. "Irreducible complexity" means, according to Behe, that there are systems in the natural world that are made up of a number of interdependent parts, and these systems are so interdependent that they cannot function without the simultaneous presence of all the components. They are "irreducibly complex", and can exist only as a total collection or not at all. As he puts it: "By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning. An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional." (Behe, p. 39)
Since the odds that all of these necessary components would have evolved all at once, intact and functional, at the same time are too improbable, and since it is impossible for them to have arisen step by step, Behe concludes, they must have been deliberately placed together by an "intelligent designer". Behe cites a number of biological processes, including the bacterial flagellum, the human immune system and the human blood clotting system, which, he says, are "irreducibly complex" and must be the product of an "intelligent designer".
Behe cites the example of a mousetrap, which, he says, must be complete with all its parts or it will not work. A mousetrap cannot appear once piece at a time -- it can only appear if all its required components are assembled, at the same time, by a guiding intelligence.
Behe's argument is not really new -- it is merely a restatement of an argument made over a hundred years ago by the British clergyman William Paley. Paley argued that if we find a watch lying on the grass, we must conclude, from the perfection and intricacy of its structure and function, that it was deliberately constructed by a designer. In the same way, Paley argued, when we look at the intricacy and perfection of the biological world, we must conclude that it, like the watch, is also the product of a designer -- the supernatural designer we call God. Paley's thesis has become known as the "argument from design".
Behe's entire argument is best viewed as a version of the "argument from ignorance". In essence, his entire argument boils down to "I can't see how this process could have evolved step-by-step, therefore it could not have." The fact that Behe (or anyone else) cannot determine how a process evolved step-by-step does not constitute evidence that it did not, however. In fact, in several of the cases that Behe cites as "irreducibly complex", new discoveries in biochemistry have indeed led to descriptions of precisely the sort of step-by-step development that Behe claimed was impossible.
In his work, Behe discounts a very important concept of biological evolution, the idea of "exaptation". This occurs when a biological trait is modified for use in a completely different system, and takes up a new function that it did not have before. Exaptations explain many of the "complex systems" we see in living things.
We can illustrate this with Behe's own example. Behe cites a mousetrap as an illustration of an "irreducibly complex system", and argues that since each component of the mousetrap -- the spring, the wooden base, the wire hammer -- is necessary for the functioning of the mousetrap, no functional trap can have developed step by step, without all of these things being present. Let us, then, show how a mousetrap could indeed evolve step by step, using exaptation.
We begin with the simplest possible "mousetrap" -- a simple piece of bait left out on the floor. When the mouse approaches the bait, we hit it with a hammer. A slight modification to our existing system. We place the bait in a small hole or hollow in the wall. This has the advantage of momentarily confusing the mouse when we surprise it at the bait, since it takes a moment for the mouse to find the exit hole, giving us more time to hit it with the hammer. Another slight modification -- we place a small metal hinged door over the opening to the hole, which swings freely back and forth. This confuses the mouse slightly more and it takes a little bit more time to find the exit -- giving us a bit more time to hit it with the hammer. Next, we add a spring mechanism that can be tripped by the mouse as it takes the bait, thus causing the door to close behind it. The advantage is that we no longer have to be waiting there when the mouse enters -- instead, the mouse is now confined and can be hit with us by a hammer at any convenient later time. Another modification: we turn the whole apparatus 90 degrees so it rests horizontally instead of vertically. In other words, our baited hole is now in the floor instead of in the wall. This has the advantage of allowing the mouse to approach our trap from any direction, instead of limiting access to just one side of the wall. Another modification: We eliminate the hole and simply place the spring door apparatus on the floor in such a way that, when tripped, the trap door slams down forcefully on the floor where the trigger is located, mashing the mouse for us when it trips the trigger. The new advantage is that we no longer have to hit the mouse with the hammer at all -- the new trap in effect does that for us. A final modification. We cut out the part of the floor that surrounds our trap and attach the trap mechanism directly to it. This allows us to deploy our trap anywhere we like, instead of limiting it to one locality.
And there we have it -- step by step development of something that is supposed to be "irreducibly complex". Each step is fully functional by itself, and in each step, the intended result is achieved -- a dead mouse. Each successive step builds upon the preceding one by small modifications, yet each step is more efficient in some way than its predecessor. And each step uses "exaptation" -- it co-opts whatever happens to be handy and incorporates it into our growing system. The bait used in the first trap can be a leftover from last night's dinner, or it could be a crumb we find behind the couch. The wall can be anywhere in the house. The free-swinging trapdoor could come from an old Coke machine, or it could be taken from the ice cube maker on the fridge. The spring can come from any bit of machinery we have around the house.
Evolution is full of examples of such exaptation, in which previously unrelated structures are incorporated into developing systems and given new functions. One example is the development of feathers for insulation in small theropod dinosaurs -- feathers which were later incorporated into wings as flying mechanisms. A particularly good example of exaptation is the therapsid-mammal fossil series discussed earlier, which shows the gradual changes that resulted from exapting the reptilian lower jawbones to work as inner ear bones instead. There is no evolutionary requirement for any of the parts to appear for the particular "irreducibly complex" purpose -- each part can appear independently for entirely separate reasons, with entirely different functions, only to be cobbled together later by evolution for a completely different purpose, just as the mammalian inner ear bones were cobbled together from jawbones that originally had nothing to do with hearing.
Another biological process, ignored by Behe, which can build "irreducibly complex" systems, is "scaffolding". This concept can be best illustrated by using the example of a stone arch, such as those built by the Romans and Greeks. It is, as any engineer knows, impossible to build a stone arch one stone at a time, since if any of the stones is missing, the stones fall apart and the arch collapses. The arch can only maintain its shape if all of the stones are simultaneously present -- a situation exactly analogous to Behe's idea of "irreducible complexity".
So how are stone arches built? With scaffolds. A scaffold is a structure, outside the structure of the arch itself, which holds all the pieces in place until the complete arch is formed, at which point the scaffolding is taken away and the arch stands on its own. Biochemical processes can follow a similar pathway.
Behe's response to exaptation and scaffolding is to argue that, even if an irreducibly complex system can be built from previously existing structures, it doesn't matter, since the previously existing structures are not the same thing as the final structure:
Q. Your argument is that, even if the type III secretory system is a pre-cursor to the bacterial flagellum, is a subset, the bacterial flagellum is still irreducibly complex because that subset does not function as a flagellum?
A. That's correct, yes. (Behe testimony, Kitzmiller v Dover, 2005)
In other words, Behe concludes, the parts that make up a flagellum aren't really a flagellum, until they become a flagellum. To which I can only reply, "No kidding".
Behe also asserted in his book that, "There has never been a meeting, or a book, or a paper on details of the evolution of complex biochemical systems." (Behe, 1996, p. 179) During his testimony at Dover, Behe also stated:
A If they could point to a paper in the literature, something that, say, Russell Doolittle overlooked which explains how complex molecular systems could be put together by gradual means, by unintelligent means, then I would be happy to agree that Darwinian evolution could explain this. But one can't issue statements and say that a theory is correct if one does not have the papers to back it up.
And you'll notice that even in this statement, you see no citations, no citations to explanations for these complex molecular systems. And in the absence of that, while that's fine for them to express their views, it doesn't mean -- it doesn't carry the weight of a single journal paper.
Q Journal papers are valuable.
A They sure are.
Q And they're just referring to the findings accumulated over 140 years, correct?
A Well, as I tried to make clear in my testimony, findings accumulated over 140 years that support the contention that Darwinian processes could explain complex molecular systems total a number of zero.
And so they -- this is another example of confusing the various aspects of evolutionary theory. It's a very difficult problem, which is why I think students should have it clearly explained to them that evolution is a complex idea, and support for change over time, or support for common descent does not run into supporting natural selection and random mutation.
Q Zero papers, Professor Behe?
A That's correct. (Behe testimony, Kitzmiller v Dover, 2005)
As a matter of fact, there have been dozens of scientific papers published concerning the evolutionary history of the "irreducibly complex" systems that Behe cites --- most of them published before Darwin's Black Box was written, and many of which were presented to Behe on the witness stand during his Dover testimony. As the judge described in his decision, "Although in Darwin's Black Box, Professor Behe wrote that not only were there no natural explanations for the immune system at the time, but that natural explanations were impossible regarding its origin. However, Dr. Miller presented peer-reviewed studies refuting Professor Behe's claim that the immune system was irreducibly complex. Between 1996 and 2002, various studies confirmed each element of the evolutionary hypothesis explaining the origin of the immune system. In fact, on cross-examination, Professor Behe was questioned concerning his 1996 claim that science would never find an evolutionary explanation for the immune system. He was presented with fifty-eight peer-reviewed publications, nine books, and several immunology textbook chapters about the evolution of the immune system; however, he simply insisted that this was still not sufficient evidence of evolution, and that it was not “good enough”. (Jones Opinion, 2005) On the stand, Behe confirmed that no scientific paper would ever be able to convince him:
Q. And I'm correct when I asked you, you would need to see a step-by-step description of how the immune system, vertebrate immune system developed?
A. Not only would I need a step-by-step, mutation by mutation analysis, I would also want to see relevant information such as what is the population size of the organism in which these mutations are occurring, what is the selective value for the mutation, are there any detrimental effects of the mutation, and many other such questions. (Behe testimony, Kitzmiller v Dover, 2005)
In effect, Behe's "irreducible complexity" is nothing but a restatement of the old ICR "what good is half an eye?" argument, applied this time to cellular structures rather than multicelled organisms. Indeed, Behe's very favorite example of "irreducible complexity", the bacterial flagellum, first appeared in a creation "science" publication, the Creation Research Society Quarterly, in June 1994, some two years before Behe offered it as evidence of Intelligent Design in Darwin's Black Box. According to the abstract of the article entitled "Not So Blind a Watchmaker", by creationist Richard D. Lumsden, Ph.D:
"Structural and operational principles underlying the organization of the vertebrate retina and bacterial flagellar apparatus are reviewed in the context of William Paley’s classic intelligent designer vs. Richard Dawkins’ contemporary "blind watchmaker" interpretations of biological origins and diversity. The significance of inverted retinal microanatomy and retinocytophysiology is diagnosed. In the process, Dawkins’ riposte to Paley is refuted. The second example is more contemporary. In terms of biophysical complexity, the bacterial rotor-flagellum is without precedent in the living world. To the micromechanicians of industrial research and development operations, it has become an inspirational, albeit formidable challenge to the best efforts of current technology, but one ripe with potential for profitable application. To evolutionists, the system presents an enigma; to creationists, it offers clear and compelling evidence of purposeful intelligent design." (Creation Research Society Quarterly, June 1994, available at http://www.creationresearch.org/crsq/abstracts/sum31_1.html)
This point that came up during DI Fellow Scott Minnich's testimony at the Dover trial:
Q. Dr. Minnich, I'm showing you a publication of the Creation Research Society Quarterly from June of 1994. Do you see that?
A. I do.
Q. That's two years before Dr. Behe published Darwin's Black Box, isn't it?
A. I'll take your word for it.
Q. You don't know what year Dr. Behe published Darwin's Black Box?
A. `96, `97, I'm not --
Q. I'd like to -- have you ever seen this publication before?
A. No, I haven't.
Q. Well, I'd like you to go to pages, there's page numbers in the upper, in the corners, in the upper corners, and I'd like you to look at pages 16 to 21. I'm not going to ask you to read it, but I'd just like you to look at it and see -- Matt, if you could page through beginning with page 16 to 21, we'll go through it, I'll invite you to read it if you'd like to, but if you see on page 16 there's a section that begins "bacterial motility"?
A. I see it.
Q. And then on the next page if you turn the page you'll see, Matt, if you can just highlight the language in the lower right-hand column? Yeah, right there, the words "bacterial flagellum," and it's a description of the bacterial flagellum in this piece of literature from this creation science organization, and then if you turn the page again to page 18, there's a description there of the bacterial flagella rotor. Can you highlight that lower paragraph there, Matt? And you'll see it says, "As resolved by electron microscopy, it consists of a series of flanges, grooves, and wheels, yes, wheels, mounted on an axil and turning on bearing surfaces with an efficiency that would be the pride of any industrial research and development operation." Do you see that?
A. I see it.
Q. And then if you'd just please turn the page one more time, there's a diagram, and it's actually Figure 9 in this, and Matt, if you could blow up Figure 9? You have to go to the next page. I'd like the language at the bottom, please. And then if you could, would it be possible to put up Dr. Minnich's slide 18?
(Brief pause.)
Q. And I'd like to ask you just to look at that. Do you see on the Figure 9 from this Creation Research Society publication that there's a picture of the motor rotor complex of the bacterial flagellum?
A. Yes, I see. . . .
Q. Now, and if you turn to page to the next page of this publication, on page 20 -- Matt, can you bring this up? On the left-hand side of the page, about one-third of the way down there's a reference there to bacterial nanomachines. Do you see that?
A. I see it.
Q. And that's the same way you referred to the bacterial flagellum, isn't it?
A. I referred to it as a nanomachine or a macromolecular machine.
Q. A bacterial nanomachine?
A. Right. That's explained in the literature, right.
Q. And then here's where the claim of essentially what I believe is irreducible complexity comes in, if you look on the right-hand side of the page it says -- it's actually the first full sentence on the right-hand side underneath the diagram, it says, "However, it is clear from the details of their operation that nothing about them works unless every one of their complexly fashioned and integrated components are in place." Do you see where it says that?
A. I see it.
Q. And then finally, and I'll bring this to a close, if you go to the abstract on the page, page 13? Matt, if you could just highlight the second half of that, beginning with the word "in terms of biophysical complexity"? I'll read it to you, it says, "In terms of biophysical complexity, the bacterial rotor flagellum is without precedent in the living world. To the micromechanician of industrial research and development operations it has become an inspirational, albeit formidable challenge to best efforts of current technology, but one ripe with potential for profitable applications. To evolutionists the system presents an enigma. To creationists it offers clear and compelling evidence of purposeful intelligent design." Do you see that?
A. I see it.
Q. . . . I'd like you to agree with me, to know whether you agree with me that that is the same argument that you have advanced here today in your direct testimony.
A. Right, I mean in terms of -- I don't have any problem with that statement. And I would add that Howard Berg at Harvard University refers to the bacterial flagellum as the most efficient machine known in the universe. So across the board whether, I don't -- what are we arguing here?
Q. I'm just, you're just confirming for me, and I think you just did, that what we have just reviewed in this Plaintiff's 853 is the, precisely the same argument that you advanced today in support of your, in your direct testimony, isn't that correct?
A. Yeah, in essence I mean I don't disagree with you. If you're trying to make a connection with creationism though I would disagree. (Minnich testimony, Kitzmilelr v Dover, 2005)
Gee, no connection THERE with creationism, is there . . . .