P-ter Accuses Me of Quote Mining

 
There are many adaptationists who recognize that random genetic drift exists. They will, when pressed, admit that neutral alleles can be fixed in a population. However, these adapationists pften maintain that visible phenotypes cannot be neutral with respect to survivability. Thus all visible phenotypes, with rare exceptions, are adaptations.

Several people have expressed this point of view in the comments on Sandwalk but the most prominent proponent is Richard Dawkins. I often use a quotation from The Extended Phenotype to demonstrate how Dawkins thinks about this issue. It comes from a chapter titled Constraints on Perfection. Here's the complete paragraph; I often use just the part that begins "The biochemical controversy ....[Richard Dawkins on Visible Changes and Adaptationism].

I have tried to show that adapatationism can have virtues as well as faults. But this chapter's main purpose is to list and classify constraints on perfection, to list the main reasons why a student of adaptation should proceed with caution. Before coming to my list of six constraints on perfection, I should deal with three others that have been proposed, but which I find less persuasive. Taking first, the modern controversy among biochemical geneticists about "neutral mutations", repeatedly cited in critiques of adaptationism, it is simply irrelevant. If there are neutral mutations in the biochemist's sense, what this means is that any change in polypeptide structure which they induce has no effect on the enzymatic activity of the protein. This means that the neutral mutations will not change the course of embryonic development, will have no phenotypic effect at all, as a whole-organism biologist would understand phenotypic effect. The biochemical controversy over neutralism is concerned with the interesting and important question of whether all gene substitutions have phenotypic effects. The adaptationism controversy is quite different. It is concerned with whether, given that we are dealing with a phenotypic effect big enough to see and ask questions about, we should assume that it is the product of natural selection. The biochemist's 'neutral mutations' are more than neutral. As far as those of us who look at gross morphology, physiology and behaviour are concerned, they are not mutations at all. It was in this spirit that Maynard Smith (1976b) wrote: "I interpret 'rate of evolution' as a rate of adaptive change. In this sense, the substitution of a neutral allele would not constitute evolution ..." If a whole-organism biologist sees a genetically determined difference among phenotypes, he already knows he cannot be dealing with neutrality in the sense of the modern controversy among biochemical geneticists.

Natural selection is the only explanation we know for the functional beauty and apparently "designed" complexity of living things. But if there are any changes that have no visible effect—changes that pass right under natural selection's radar—they can accumulate in the gene pool with impunity and may supply just what we need for an evolutionary clock.

Richard Dawkins
The Extended Phenotype (2005)I have discussed this quotation with Richard Dawkins and I am convinced that it fairly represents his viewpoint. The only quibble would be that Dawkins would probably admit of one or two exceptions where neutral alleles might produce a phenotypic effect. In other words, his statement above is perhaps an example of hyperbole but that's how I always read it anyway. Almost all popular science writers make generalizations of this sort and it's not a great crime.

The bottom line is that Dawkins thinks that neutral mutations cannot have an effect on embryonic development; therefore, they cannot result in a visible phenotype. Dawkins believes that almost all visible mutations will have either a beneficial or a detrimental effect on the survivability of an organism and that neutral mutations are a phenomenon that's confined to the molecular level where they may not even count as evolution.

P-ter thinks that I misrepresent Dawkins by quote mining [Larry Moran caught quote mining]. Here's what P-ter says,

This certainly seems to place Dawkins as an "adaptationist", one who thinks that all differences in phenotypes are adaptations. I was a little surprised by this, but the quote seemed clear, and I wasn't going to take the time to find my original.

Luckily, another commenter pointed out that The Extended Phenotype is searchable at Google Books [The Extended Phenotype]. And funny, the very next line after Moran stops quoting is possibly relevant:

The next lines P-ter is referring to is the beginning of a new paragraph ...

He might, nevertheless, be dealing with a neutral character in the sense of an earlier controversy (Fisher & Ford 1950; Wright 1951). A genetic difference could show itself at the phenotypic level, yet still be selectively neutral.

P-ter then continues with ...

Dawkins goes on to express some skepticism about some arguments for evolution by drift, but he's certainly not an "adaptationist" in the Moran sense.

I suppose I'm somewhat naive: distorting someone's argument through selective quotation is a classic creationist tactic, and Moran has written a bit about the propaganda techniques used by that crowd. Little did I know his familiarity is not of an entirely academic sort.

[1] As opposed to "pluralists", as he likes to call himself. For someone who (rightfully, in my opinion) is disdainful of "framing" (the view that scientists need to spin their results in order to resonate better with the public), he certainly knows how to frame.

This is a very serious charge. I'm accused of deliberately distorting Dawkins' position by selective quotation. According to P-ter, Dawkins does not believe what he says in the quoted paragraph. (And elswhere, I might add.) According to P-ter Dawkins believes that mutations with a visible phenotype can be neutral. (We're not talking about one or two exceptions here, we're talking about the generality that applies to a significant percentage of mutations.)

P-ter's evidence of the crime of quote mining is the first two sentences of a paragraph that appears on the bottom of page 32. You can read it for yourself but it seems obvious to me that Dawkins is raising a possible objection to his claim and then dismissing it. Here are the first few (not just two) sentences of that paragraph: I think they convey the correct intent.

He might, nevertheless, be dealing with a neutral character in the sense of an earlier controversy (Fisher & Ford 1950; Wright 1951). A genetic difference could show itself at the phenotypic level, yet still be selectively neutral. But mathematical calculations such as those of Fisher (1930b) and Haldane (1932a) show how unreliable human subjective judgement can be on the "obviously trivial" nature of some biological characters. Haldane, for example, showed that, with plausible assumptions about a typical population, a selection pressure as weak as 1 in a 1000 would take only a few thousand generations to push an initially rare mutation to fixation, a small time by geological standards. It appears that in the controversy referred to above, Wright was misunderstood (see below) ...

A careful reading of Dawkins shows that the objection to his claim doesn't stand because people misunderstood Wright. Thus, according to Dawkins, characters that appear to be neutral really aren't.

I maintain that my original characterization of the Dawkins' position is accurate and his words reflect his true beliefs. I resent P-ter's accusation that I deliberately tried to misrepresent Dawkins by quoting that passage.

Incidentally, P-ter puts words in my mouth. I recognize several different kinds of adaptationist. The worst of them are those who think every visible phenotype is an adaptation of some sort but there are many who do not hold this extreme position. It's simply not true that I say every adaptationist must deny the fixation of neutral alleles with a visible phenotype. Some are easier to mock than others, but it's pretty easy to get most of them going whenever I point out that Dawkins is an adaptationist.