Behe, a biochemist and author of Edge of Evolution comments on an expanded version of a short essay called “Irremediable Complexity?” featuring prominent evolutionary biologist W. Ford Doolittle as an author. The short version was published last year in Science – the expanded version is in IUBMB Life:
“Irremediable Complexity” (9 August 2011)
… the gist of the paper is this. The authors think that over evolutionary time, neutral processes would tend to “complexify” the cell. They call that theoretical process “constructive neutral evolution” (CNE). In an amusing analogy they liken cells in this respect to human institutions:
Organisms, like human institutions, will become ever more ”bureaucratic,” in the sense of needlessly onerous and complex, if we see complexity as related to the number of necessarily interacting parts required to perform a function, as did Darwin. Once established, such complexity can be maintained by negative selection: the point of CNE is that complexity was not created by positive selection. (1)
In brief, the idea is that neutral interactions evolve serendipitously in the cell, spread in a population by drift, get folded into a system, and then can’t be removed because their tentacles are too interconnected. It would be kind of like trying to circumvent the associate director of licensing delays in the Department of Motor Vehicles — can’t be done.
The paper appear to want to avoid claiming the impossible – that Darwinian evolution can evolve complex systems by accident, and the authors hope neutral evolution can do it. Behe asks,
Is this a reasonable hypothesis? I don’t mean to be unkind, but I think that the idea seems reasonable only to the extent that it is vague and undeveloped; when examined critically it quickly loses plausibility. The first thing to note about the paper is that it contains absolutely no calculations to support the feasibility of the model. This is inexcusable.
The mutation rates of various organisms — viral, prokaryotic, eukaryotic — are known to sufficient accuracy (5) that estimates of how frequently the envisioned mutations arrive could have been provided. The neutral theory of evolution is also well-developed (6), which would allow the authors to calculate how long it would take for the postulated neutral mutations to spread in a population. Yet no numbers — not even back-of-the-envelope calculations — are provided.
Previous results by other workers (7-9) have shown that the development of serendipitous specific binding sites between proteins would be expected to be quite rare, and to involve multiple mutations. Kimura (6) showed that fixation of a mutation by neutral drift would be expected to take a looong time. Neither of these previous results bodes well for the authors’ hypothesis.