Young Australian Skeptics

This article is the third in a series about typical arguments that creationists use to try and undermine the theory of evolution. The previous two articles are An Introduction to Christian Creationism and Creationist Argument — Mutations Cannot Increase Information: it is advised to read them before reading this.

Today’s article revolves around one of the primary arguments of the Intelligent Design movement: the argument from irreducibly complex structures and systems. First coined by Michael Behe in his 1996 book “Darwin’s Black Box”, this argument is a staple in debates between creationists and evolution supporters.

So, what is Irreducible Complexity (henceforth referred to as IC)? Let’s let Michael Behe himself help define it for us.

“A single system which is composed of several 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, pg. 39

This is usually illustrated with the example of a mousetrap as the IC system. The function of the mousetrap is to kill mice, and all of its parts must be present and in their correct positions for it to fulfil this function. Removing any one part will cause the mousetrap to become ineffective, and thus it is defined as irreducibly complex: its form cannot be reduced any further if it is to continue functioning correctly.

IC systems, says Behe, exist at the cellular and biochemical level inside all living things. And if they cannot function correctly when one part is absent, how could they have evolved by a gradual process, whereby parts are slowly added until the system is complete? Such is the IC argument.

So, what are the problems with this argument? What I like to do with all creationist arguments I come into contact with is to examine the premises they stand on. If any of them can be shown to be false, then, of course, the argument is fundamentally flawed and cannot be used to support anything.

The premises of IC that most intelligent design proponents will admit to are:

- According to current evolutionary theory, all intra-​​organism biological systems evolved through the gradual addition of parts through genetic mutation and natural selection.

- Incomplete systems without functions are not selected for by natural selection.

- Some of said systems cannot function without all of their parts in place.

All of these premises are true. So, what’s the problem with IC? Well, there’s another, hidden, premise that exists within the dark corners of IC argument. This premise must be true for the argument to hold up, but is strangely never talked about by the people who use IC to support intelligent design. It is:

- Incomplete systems cannot have any function.

This is obvious, if you spend a little time thinking about it. One of the premises clearly states that systems without functions are not selected for by natural selection, yet an incomplete system, looking from the present to the past, is only functionless relative to the function that it has now. Just because a system does not have its current function, that does mean it did not have a different function in the past, one that would have allowed natural selection to favour its existence within the organism.

This can, of course, be illustrated with the mousetrap example. The function of a complete mousetrap is to kill mice. But, if you remove multiple parts, eg. everything but the wooden base, it can still have a function in your home: being a doorstop. In fact, a complete mousetrap can also act as a doorstop. Ah ha! Now we can hypothesise about a possible route that the evolutionary development of the mousetrap took, using the function of “doorstop” as a scaffolding. The extra parts of the mousetrap could be added whilst it acted as a doorstop, thereby providing a constant selective advantage to having the mousetrap in your house.

So, IC systems do exist, but they can evolve naturally. The IC argument makes the mistake of presuming that the existence of IC systems is evidence against evolution, but the lack of a certain function does not preclude the existence of other functions. Primative feathers can insulate, primative eyes can detect the direction of light without having the ability to form an image, and parts of the bacterial flagellum can be used as a toxin injection system.

Part of the IC argument also revolves around an argument from ignorance: the logical fallacy that because something is not known or explained, a certain notion is therefore correct. If evolution cannot explain the origin of an IC system, it is an argument from ignorance to say that that constitutes positive evidence for intelligent design.

In short, irreducible complexity falls flat as an argument against evolutionary theory. However, creationists and intelligent design proponents still use it as an argument, for reasons unknown. But don’t worry, because now, if you are confronted with this argument, you can refute it, using the information in this article.

If you have any questions about irreducible complexity, feel free to post a comment below or start a new thread in the Young Australian Skeptics forum.

Tags: Creationism, Evolution, Intelligent Design, Irreducible Complexity

This entry was posted on Tuesday, December 30th, 2008 at 8:00 am and is filed under Creationism, Evolution, Jack Scanlan, Pseudoscience. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.