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At BioLogos, Confusion over the Meaning of “Irreducibly Complex”

A correspondent recently pointed out to me that Dennis Venema, associate professor of biology at Trinity Western University, has posted a series of essays criticizing my work on irreducible complexity and intelligent design at the theistic-evolutionary website BioLogos. Although I don’t usually respond to arguments that are simply posted on blogs (life is too short), I’ll give a brief reply here.

I’ve read Professor Venema’s six posts and all of the comments. Most of the pro-ID points are right on the money. However, there are a couple of points that no one mentioned that I think are important for the discussion.

First of all, Venema confuses “irreducibly complex” with “essential for the viability of the organism.” The two concepts are not the same. For example, a person can survive with a missing blood clotting factor, where the IC clotting system is broken. Thus the factor is needed for the clotting system to work, but is not necessary for the viability of the organism. On the other hand, a factor can be essential for life but not irreducibly complex. A simple example is hemoglobin. It is not IC, but an organism will die without it. Thus Venema is mixing up concepts. An IC system (like a mousetrap) cannot work if a piece is removed. An organism, even a dying one, will survive a while if, for example, its lungs are pulled out.

Professor Venema discusses several proteins from the fruit fly called “p24-2” and “Éclair,” which are very similar to each other and very likely arose through gene duplication. Venema claims the proteins are part of an irreducibly complex system, and that the new, duplicated protein is a new part of that system. Some pro-ID commenters at the site rightly take Venema to task for not spelling out what the ID system is, but that point should be pounded home much more. The putative new binding site of p24-2 that Venema emphasizes is likely not a necessary part of the overall IC system.

Let me explain. Suppose as Professor Venema does, that Eclair and p24-2 are parts of systems that transport specific other proteins that they bind in the cell. Imagine an analogous mechanical system that has a rotating metal wheel at the top of a pole. To two places on the wheel are attached wires that at the bottom hold a claw that has an oval hole in it. When the wheel rotates, every half turn it encounters a metal bump which pushes up the wire and causes the claw to open. Once it passes the brief bump, the claw closes. During that time the claw can pick up an object that has a part of it shaped like the oval hole in the claw. As the wheel makes another half turn, it encounters a small depression, which causes the wire to dip down, opening the claw, and releasing the object. At the other end of the oval-shaped object is a little array of magnets, that match a second object. That second object gets transported with the claw, attached to the magnetic end of the oval shaped object.

Now what we have here is an already-intact transport system. At best, the amino acid changes in p24-2 would be analogous to re-arranging the magnets at the end of the oval-shaped object, so that it could transport a different object than before. But that is just taking advantage of an already-existing IC system; it is not a new one. As the old adage goes, Darwinian evolution is a tinkerer. It can fiddle a bit with pre-existing IC systems, but is incompetent to build new ones.

A final point is that there are five specific amino acid differences between Eclair and p24-2. Professor Venema emphasizes that they apparently comprise a new binding site. However, he seems not to notice that they may not have arisen by random mutation. Once one gets beyond one or two random mutations, one can’t assume that multiple further mutations arose by chance. In other words, as far as anyone knows, those five point mutations (or a subset of them) may have required guidance or design in their appearance.

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.