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. An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution. Since natural selection can only choose systems that are already working, then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on.A recent paper published in Cellular and Molecular Life Sciences has attracted the attention of the Intelligent Design Creationists because it mentions irreducible complexity. According to Denyse O'Leary (? News) the paper "uses “irreducible complexity” in same sense as ID theorist Behe?" [see Refereed paper in Cellular and Molecular Life Sciences uses “irreducible complexity” in same sense as ID theorist Behe?].
That's interesting. Let's look at the paper to see what it says. The reference is Muskhelishvili, G. and Travers, A. (2015) and the relevant passage is on page 4556.
Thus, the holistic approach assumes self-referentiality (completeness of the contained information and full consistency of the different codes) as an irreducible organisational complexity of the genetic regulation system of any cell. Put another way, this implies that the structural dynamics of the chromosome must be fully convertible into its genetic expression and vice versa. Since the DNA is an essential carrier of genetic information, the fundamental question is how this self-referential organisation is encoded in the sequence of the DNA polymer.What they are saying is that proper gene regulation requires both transcription factors AND a particular organization of the chromosome that facilitates transcription. It also requires input from metabolic pathways. If any one of these three things are missing then the cell cannot regulate gene expression in the same manner as cells where all three are present.
The authors then go on to discuss how this system could have evolved. Look at Figure 3 of their paper (below) where they clearly show the relationships between transcription, supercoiling, and small regulatory molecules. The paper describes their belief that this "irreducible organisational complexity" arose by evolution from these three existing features.
So, these authors are using "irreducible complexity" to describe a system that's clearly possible according to their understanding of evolution. Uncommon Descent states that this is exactly the same sense in which the term is used by Michael Behe. In fact, it quotes a physicist named David Snoke who says,
Three comments: 1) the authors are “serious” scientists, not fringe people. 2) They are using “irreducible complexity” in the same sense as Behe. This is not a case of accidental use of the same phrase to mean something different. Their term “holistic” is another way of saying the same thing, that the system requires all of its parts to work. 3) This “holistic” approach is one that is becoming common in systems biology. I have a paper coming out on that, in the works.We've been telling Intelligent Design Creationists for years that irreducibly complex systems can easily arise by naturalistic processes (i.e. evolution). I'm really glad that they have finally seen the light.
That should be the end of any more posts saying that irreducibly complex systems can't evolve.
(Not holding my breath.)
Muskhelishvili, G. and Travers, A. (2015) Integration of syntactic and semantic properties of the DNA code reveals chromosomes as thermodynamic machines converting energy into information. Cell. Molec. Life Sci. 70:4555-4567. [Abstract]