Michael Denton’s new book, Evolution: Still a Theory in Crisis, is stirring controversy. For example, over at University of Toronto biochemist Larry Moran’s blog, Sandwalk, a debate over what drives evolution — natural selection or genetic drift — is going on.
Natural selection is, of course, the means by which evolution is supposed to receive its direction, from less fit to more fit organisms. Of all the forces proposed by modern biologists to drive evolution, natural selection is the only one that could impart directionality; in contrast, genetic drift introduces the element of chance.
Genetic drift has a stronger effect than natural selection in vertebrate and invertebrate populations, whose effective population sizes are on the order of 10^6 to 10^4 breeding individuals. Many scientists go so far as to say that most molecular changes in these species are the result of non-adaptive, neutral processes (driven by chance), rather than adaptive processes (driven by natural selection). Such chance processes provide the grist for the mill of natural selection to refine at the phenotypic level, so it is said. Such scientists include Michael Lynch, Denis Noble, Eugene Koonin, Eva Jablonka, and Masatoshi Nei.
Professor Moran is another. He writes:
Readers of this blog will know that I’m a fan of Evolution by Accident. I don’t think that the history of life can be explained in strict Darwinian terms (i.e. natural selection) and I think that modern evolutionary theory includes Neutral Theory and a major role for random genetic drift.
This is the view of many modern evolutionary biologists. Their work and views have been reported frequently on Sandwalk over the past ten years but you can find it in all the evolutionary biology textbooks. I’m just the messenger here. It’s evolutionary biologists who have made the case for non-adaptive evolution beginning long before The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme.
The problem arises for Moran when fellow scientists refuse to accept the role of non-adaptive, neutral processes as a part of evolution. But he then goes on to say that intelligent design scientists think likewise.
Trying to convince others of the truth of non-adaptive evolution has been a frustrating experience. It’s been particularly frustrating when dealing with Intelligent Design Creationists who think that evolution by natural selection is the only game in town. They are the most adaptationist people on the planet even though they don’t actually believe in the scientific version of evolution.
He acknowledges that Michael Denton, recognizing that adaptation is not the only game in town, attributes evolution to non-adaptive processes distinct from known evolutionary processes. He wraps it up by saying that Denton thinks, “Therefore, gods did it.”
But now we have an entirely new phenomenon. Michael Denton recognizes how silly it is to attribute every feature to adaptation. This is, of course, a view that been around for a long time among evolutionary biologists and they have perfectly naturalistic, non-adaptive, explanations that have been published in thousands of scientific papers. Denton won’t acknowledge that.
Most creationists won’t even admit that there are features that don’t appear to have been designed for functionality but here’s Denton showing them that they’ve been wrong for decades. When I tried to do that I met with huge resistance because I was trying to show them that their view of evolution is wrong. Denton takes a different approach. He assures them that their extreme Darwinian view of evolution is correct and the presence of non-functional features — like the shape of a maple leaf — is something that “evolution” can’t explain. Therefore, gods did it. [Emphasis added.]
There are so many things wrong with these paragraphs that it’s hard to know where to start. First, intelligent design proponents know that evolutionists propose more than natural selection is involved in explaining the patterns we see in life — that there are neutral forces proposed to be at work.
I personally have written multiple posts on this, available here, here, and here. The problem is this. Neutral or nearly neutral processes boil down to chance, and chance is a pretty poor explanation for the order and complexity we see in life. It’s like saying luck will provide the ingredients that can be turned into a cake. In other words, luck will provide the ingredients to build the spliceosome, or the ribosome, or the complex gene regulatory circuits in eukaryotic cells. The thing is, there is nothing for natural selection to work on until these systems are assembled. Similarly, luck is proposed to allow the assembly of an invertebrate embryo that is capable of developing into a reproductive adult. Of course, there is no natural selection until reproduction is possible, so it’s all up to luck to get there.
Second, Denton certainly is not a pan-selectionist. He believes that natural selection is powerless to generate the discontinuous patterns we see in life. But neither does he believe that non-adaptive, neutral forces like drift can account for it. To quote from his book:
If gradual natural selection is powerless to generate the most important biological features in the history of life, as I have argued in previous chapters, then what about relying on chance saltations as an alternative mechanism? …[T]he sheer complexity of biological life renders such a proposal incredible. Chance cannot resuscitate the corpse of Darwinian evolution. [p. 225]
The complexity of living systems is so great that there is now an almost universal consensus, as we saw in the discussion of ORFan genes, that the simplest of all biological novelties — a single functional gene sequence — cannot come about by chance mutations in a DNA sequence. And if an individual gene sequence is far too complex to be produced by chance, then the sudden origination of a morphological novelty like a feather, a limb, or even such a comparatively simple novelty as an enucleate red cell — all novelties vastly more complex than an individual functional gene sequence — is by any common-sense judgment far beyond the reach of any sort of undirected “chance” saltation.” [p. 226]
According to Denton, and all intelligent design proponents I know, neither selection nor drift can account for major transitions during evolution. Denton does allow that it is theoretically possible that if “a long sequence of transitional adaptive forms” were potentially able to produce a complex biological feature, natural selection might accomplish the task. But he does not say this is likely, nor does he attribute the arrival of novelties to “gods,” as Moran claims. From Denton:
…[C]umulative selection can be the causal agency responsible for the creation of a complex biological novelty if the novelty can be reached via a long sequence of transitional adaptive forms. But if the novelty cannot be actualized in this way, either because it is obviously a non-adaptive Bauplan (like the tetrapod limb, or the angiosperm flower) or because no adaptive intermediates can be conceived of (as in the case of adaptations like the bat’s wing or human language), it is no use turning to undirected chance saltations or “hopeful monsters” as a way of making the leap, as some authors do. If cumulative selection has no functional continuums to traverse the gaps, or if a novelty appears to be a non-adaptive ground plan, then it could only have been actualized by some directive agency other than cumulative selection. [p. 228]
For him, the directive agency is the emergent behavior of natural forms.
There is increasing evidence — perfectly consonant with the structuralist view — that a great deal of organic order is emergent, the result of the self-organization of different categories of biomatter and not specified in the genes as the alternative Darwinian contingent model predicts. There is the evidence of evo-devo that the paths of evolution have been constrained by deep homologies, shared in some cases by all metazoan organisms, and that the specific taxa-defining novelties themselves have been shaped largely by internal causal factors rather than cumulative selection. Finally, there is the existential challenge to Darwinian functionalism posed by the non-adaptive nature of so many of the homologs and Bauplans. [p. 279]
But Denton is also not averse to intelligent design:
…[R]andom trial and error could never have actualized the sorts of complex adaptations that permeate the entire living kingdom from the molecular to the organismic levels. But many authors in the intelligent design (ID) movement have ably presented this argument over the past decade. [p. 28]
And in another place:
It is important to stress that structuralism… implies that organic order is a mix of two completely different types of order, generated by two different causal mechanisms: a primal order… [including the taxa-defining homologs] generated by natural law, and a secondary adaptive order imposed by environmental constraints (by natural selection according to Darwinists, by Lamarckian mechanisms and by intelligent design according to current design theorists). The adaptive order of living things [which serves specific immediate environmental constraints] represents a completely different sort of order, outside of the explanatory framework of structuralism altogether. This means that structuralism per se can never give a complete causal explanation for all organic order. Structuralism is NOT a biological theory of everything. [p. 18]
He then says:
The origin of the natural laws that generate the primal order is, of course, its own important question. As I and others have argued elsewhere, those laws may point to the intelligent design of the universe as uniquely fit for life. Bur arguing that thesis is not the purpose of this book. [p. 18]
All I can say is, Moran must have engaged in very selective reading of Denton’s book to make the claims he does. He misrepresents what intelligent design proponents think, and he attributes to Denton a point of view and motive that is incorrect. Denton does not believe that gods did it, nor does he tell design proponents that. All Moran gets correct is that we all doubt the ability of natural selection or genetic drift to drive the evolutionary process.
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