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"Complexity by Subtraction": In Evolutionary Biology, a Devilishly Subversive Suggestion

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A theme in Stephen Meyer's forthcoming book, Darwin's Doubt (June 18), is that we already live in a post-Darwinian world. This will come as a shock to those low-information science consumers who follow trends in biology through the popular media, textbooks, Darwin activist blogs and the like. From such sources, it might appear that Darwinian theory is scientifically unassailable. (Yet even in those venues, cracks are seen in the fa├žade; recall, for example, Laurence Moran's recent admission of Darwin doubts.)

DD web ad v.1.3.jpgIt's quite different in the technical literature on evolutionary biology, Meyer writes. There it's apparent that plenty of top researchers have already stepped over the debris of Darwinism, making no secret of it either, and begun exploring alternatives. A new article in Evolutionary Biology offers a great illustration.

Duke University biologist Daniel W. McShea and his colleague Wim Hordijk have wised up to the reality that Darwinian evolutionary gradualism is not an adequate explanation of complex structures in living creatures. As Michael Behe showed in Darwin's Black Box, irreducible complexity is rife in biology, and it resists orthodox evolutionary explanations. If it didn't resist, there would be no reason to propose an alternative, as McShea and Hordijk do.

In "Complexity by Subtraction," they argue that rather than being built up as normally imagined by Darwinists, from simple to complex, evolution may happen the opposite way. Starting out with something highly complex, there follows a loss of complexity, and you end up with an evolutionary product that is simpler and more streamlined. Where did you get the highly complex beginning? That must remain the usual free gift. From the Abstract:

The standard [Darwinian] thinking could be right, even in general. But alternatives have not been much discussed or investigated, and the possibility remains open that other routes may not only exist but may be the norm. Our purpose here is to introduce a new route to functional complexity, a route in which complexity starts high, rising perhaps on account of the spontaneous tendency for parts to differentiate. Then, driven by selection for effective and efficient function, complexity decreases over time. Eventually, the result is a system that is highly functional and retains considerable residual complexity, enough to impress us.
Notice the hedging, the hardly veiled hints at what you once would have thought were unspeakable ideas. The standard Darwinian story "could be right, even in general." Meaning that it could be wrong, completely wrong. "Other routes... may be the norm"!

Evolution by loss of information or loss of function, of course, is an idea that's familiar to ID theorists and Darwin advocates alike. A familiar example is the blind cavefish that lost function in its eyes over time because, living in the dark, it can easily tolerate mutations that lead ultimately to blindness. That's straightforward. The problem is always explaining how biological information or function is built up in the first place.

An article at PhysOrg offers this candid reflection, making clear that the McShea and Hordijk article is a response to intelligent design theory ("Study proposes alternative way to explain life's complexity"):

Some biological structures are too dizzyingly complex to have emerged stepwise by adding one part and then the next over time, intelligent design advocates say. Consider the human eye, or the cascade that causes blood to clot, or the flagellum, the tiny appendage that enables some bacteria to get around. Such all-or-none structures, the argument goes, need all their parts in order to function. Alter or take away any one piece, and the whole system stops working. In other words, what good is two thirds of an eye, or half of a flagellum?
Mere "complexity" isn't exactly the right way to describe the quality in such structures that makes them other than amenable to Darwinian explanation, but never mind that. As ENV pointed out the other day, real biologists are still trying to answer the challenge laid down by Behe, even as Darwin activists assure the public that there was no serious challenge to begin with ("Taking on Behe's Challenge: Evolve Me a Cilium"). Going on, the article summarizes the proposal by McShea and Hordijk:
Instead of emerging by gradually and incrementally adding new genes, cells, tissues or organs over time, what if some so-called "irreducibly complex" structures came to be by gradually losing parts, becoming simpler and more streamlined? Think of naturally occurring rock arches, which start as cliffs or piles of stone and form when bits of stone are weathered away. They call the principle "complexity by subtraction."
This is all very revealing. In the geological context, we know very well how, as a starting point, "cliffs or piles of stone" form. It's readily comprehensible how, worn by water or weather, an arch may appear. In the biological context, we do not know how the starting point -- functioning "genes, cells, tissues or organs" -- got there.

On an initial consideration, the McShea/Hordijk paper seems devilishly subversive. Even as the authors pay lip service to Darwinian theory -- in the context of the evolution of the eye, "Even a very simple eye with a small number of parts would work a little. It would be able to detect shadows, or where light is coming from," McShea observes -- their "alternative" to the standard story implicitly points to the inadequacy of the original, Darwinian evolutionary theory.

If it were feasible to build up complexity per the usual narrative, there would be no need to offer an alternative that turned the original on its head. Would there?

Image: Paola Rosa/Flickr.