Jonathan McLatchie is an Intelligent Design Creationist who now blogs frequently on the Discovery website Evolution News [sic]. His latest post is How NOT to Argue Against Irreducible Complexity where he defends the claim that the human male reproductive apparatus is irreducibly complex and therefore must be a product of intelligent design.

You can read the post yourself to see how ID proponents argue. I want to make another point.

McLatchie thinks that the irreducible complexity argument is very powerful evidence for intelligent design. He writes,

The argument from irreducible complexity against evolution and for design has always held strong intuitive appeal for me, and it has hence become my argument of choice in discussions about the scientific merits of evolution versus design.

Let's look at the logic of the argument from irreducible complexity. Assume that we have identified a structure that's irreducibly complex. There are three possible ways to deal with its origin.

1. There is a plausible naturalistic explanation for the evolution of the irreducibly complex structure.
2. There is currently no detailed naturalistic explanation that accounts for the evolution of the irreducibly complex structure.
3. It is impossible for there to ever be a naturalistic explanation; therefore, god did it.

We know that there are good naturalistic explanations for the evolution of irreducibly complex structures. In fact, McLatchie mentions some of them that refuted his earlier claims. Behe has also backed off some of his claims in light of evidence that irreducibly complex structures can evolve without the help of god(s). This establishes that the mere existence of an Irreducibly Complex Structure is not evidence for intelligent design.

Even if a system is irreducibly complex (and thus cannot have been produced directly), however, one cannot definitively rule out the possibility of an indirect, circuitous route.

In some cases there is currently no good naturalistic explanation for the evolution of an irreducibly complex structure. This could be due to a real difficulty in coming up with a plausible scenario or it could be due to the fact that no scientist has bothered to do the investigation required because they don't care. In either case, the current lack of an explanation is not, in itself, evidence for an intelligent designer.

The third possibility is the one that counts. If you can prove that a naturalistic explanation is impossible then there must be a non-naturalistic explanation such as aliens, or god(s). McLatchie says the the sperm flagellum is irreducibly complex and that he cannot imagine how it could have evolved naturally. According to creationist logic, it follows that some alien, or some god, must have designed the original sperm flagellum.

McLatchie won't tell us when this happened or why the intelligent designer was so interested in sperm, but that's typical of Intelligent Design Creationsts—they require detailed explanations from scientists but not from their fellow creationists.

• Jonathan McLatchie explains irreducible complexity
• The science behind Intelligent Design Creationism
• The meaning of "irreducible complexity"
• A Torley Defense of Irreducible Complexity
• Barry Arrington Explains Irreducible Complexity
• Irreducible Complexity