CA51 Irreducible Complexity

Irreducible complexity (IC) has become one of the most popular arguments in favor of intelligent design, if not the most popular. The biochemist and ID proponent Michael Behe coined the term in his book Darwin’s Black Box, bringing the notion of IC to prominence. Certain biological systems, the argument goes, cannot have evolved by small changes through natural selection. If it could be demonstrated that there are irreducibly complex structures in nature, we would have a serious challenge to evolution by natural selection. Darwin wrote, “If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.” However, Darwin’s next sentence was, “But I can find out no such case.” Not only has no such case been found out, there are deeper conceptual problems with irreducible complexity that we’ll explore.

I have an episode forthcoming on Darwin Devolves, Behe’s new book, but it was necessary to talk about IC first. I would also plug Richard Dawkins’s books if you’re looking to inoculate yourself against creationist nonsense generally. Climbing Mount Improbable, which came out in 1996, and The Blind Watchmaker, which came out in 1986, are both decisive smackdowns of the concept of intelligent design generally and IC specifically, since neither of those ideas are actually new; and the God Delusion deals with those subjects the most directly.

Though the term ‘irreducible complexity’ was coined by Behe in 1996, the underlying idea is an old and familiar one. As P.Z. Myers aptly explained, the creationist argument is and always has been some version of: “‘Complexity, complexity, complexity complexity. Oh look, there’s a pathway — it’s very complicated. Complexity! Complexity, complexity complexity — complexity. And did you know that cells are really, really complicated? But we’re not done — complexity! Complexity (complexity complexity). And you’re gonna be blown away by the bacterial flagellum — it’s like a little machine! And it’s really, really complicated! Complexity-complexity complexity. Complexity. We need more cells, they’re really complicated. You just get blown away by these things, they are just so amazingly complicated. Complexity. Therefore; design.’ You’ve heard it all now.”

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Irreducible Complexity [wiki]

Nathan Lents – Darwin Devolves [Science Mag]

Exaptation 101 [LiveScience]

Irreducible Complexity – Rationality Rules [YouTube]

Francis Collins – The Language of God [Amazon]

Kenneth Miller – Finding Darwin’s God [Amazon]

Richard Dawkins – Climbing Mount Improbable [Amazon]

Richard Dawkins – The Blind Watchmaker [Amazon]

Richard Dawkins – The God Delusion [Amazon]

Michael Behe – Darwin’s Black Box [Amazon]

Homunculus Argument [wiki]

2 thoughts on “CA51 Irreducible Complexity

    1. Thanks for the link. I’ll have to address this article in the next episode on IC, which I’m currently writing. He definitely acknowledges exaptation (though not by name), but I would not say he addresses it substantively. He merely hand-waves in all the quotes from the EN article, rejecting it based on his personal incredulity and the claim that exaptation is too “vague”. I think both of these are easily answerable (and I dealt with both in the original IC ep, though not in those exact words).
      In Darwin’s Black Box, Behe writes, “As the complexity of an interacting system increases, though, the likelihood of such an indirect route drops precipitously.” I don’t believe such a claim can be made by someone who actually understands exaptation. Many genes, traits, structures, functions, etc. are there for another reason ahead of time, before the new selective pressure is present. The claim that the likelihood of an indirect route drops as complexity increases is to not understand exaptation. Moreover, the phrase “indirect route” seems to indicate Behe’s fundamental misunderstanding/misreading of evolution. It just seems like Behe can’t get goal-directed evolution out of his head.
      There’s a book of essays called Philosophy of Biology, collected by Alex Rosenberg (, to which Michael Behe contributed. I’ll be going through his paper in the future IC episode. There he defends his claims against exaptation in more detail, and I’ll be reading from his essay.

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