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Health

Evolution is not the change in allele frequencies?

Gene ExpressionBy Razib KhanJanuary 28, 2008 3:20 AM

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In The Hopeless Monster? Not so fast! Bora says:

In a back-and-forth with a commenter, Coyne defends himself that he is talking about the changes in genes, not evolution. This just shows his bias - he truly believes that evolution - all of it - can be explained entirely by genetics, particularly population genetics.

His preferred definition of evolution is probably the genocentric nonsense like "evolution is a change of gene frequencies in a population over time".

I prefer to think of it as "evolution is change in development due to ecology" (a softening of Van Valen's overly-strong definition "evolution is control of development by ecology"). Population genetics is based on the Hardy-Weinberg equilibrium - pretty much all of it is a build-on and embellishment of it. Population geneticists tend to forget, once they get into complex derivations of HW, that HW has about a dozen completely unrealistic assumptions underlying it. Now, in a case-to-case basis, some of those assumptions can be safely ignored, some can be mathematically taken care of, but some are outside of the scope of mathematics (or at least the kind of math that can be integrated into the development of HW). Those are ignored or dismissed and, if this is pointed out by those working on evolution from a Bigger Picture perspective, met with anger.

First I would like to observe that the HW is the jumping off point for many models, but obviously population genetics' bread & butter explores the large space of deviations from that ideal (i.e., a population at HW equilibrium is not subject to selection, mutation, migration, etc.). I think Bora's exposition here would definitely mislead; don't confuse the brick for the house. But is this "nonsense"? I'm not very "religious" about the whole "evolution is change in allele frequencies" or it isn't debate; other definitions just don't seem as clear and useful, but I'm willing to entertain them. Also, Bora's fixation on "genocentrism" is often hard to figure out, but I really stopped paying attention to that when he started posting strange things like Genocentrism aids Anti-Abortion Arguments. I am asking for an intervention if I ever post something titled "Evo-devo supports Fabian socialism," just so you know. Since a fair number of evolutionary biologists read this bog, I'd like some input on the whole "evolution is allele frequencies" debate. Because I tend to think from a genetic angle in terms of models and formalisms operating upon them it makes sense that this is a clear way for me conceptualize the issues (I mean, to a great extent population genetics has always been rooted in the allele frequency line of thinking). But I am interested in what others have to say, as my interest in paleontology of late should make clear. The standard population genetic definition captures the essential point about heritable transmission; which seems critical to highlight in any biological evolutionary context. It's a clear & distinct idea. But that doesn't mean that other ideas don't offer value-add in terms of insight or utility in their own contexts of course, I just don't know as much about alternatives. Note: I am aware of those who argue that gene-gene interactions & networks really modify the "change in allele frequencies" mantra, I definitely think there is something to that (I have a strong interest in statistical epistasis). But that seems to just a variation of the "genocentric" outlook. We're starting with the same brick and just assembling a bit differently. Sewall Wright was one of the founders of population genetics and for most of his career gene-gene interactions were central elements within his substructure based models. Update:Greg Laden weighs in:

In the end, however, there is a larger question: What the hell are you'all talking about anyway? I find that the discussion of "hopeful monsters" and saltational evolution has not addressed the essential, fundamental question of adaptation. This may be because most of the people who are talking about it are not adaptationists, and the current trend in the blogosphere is to be anti-adaptationist (it seems to me). But this is a conversation about adaptations and how they arise, so this is something we should talk about.

Right. Bora has a tendency to talk about "nonsense" or how "old-fashioned" "genocentrism" is, but I really don't get a clear sense of what he's positing to replace it. To say, for example, that multi-level selection is the future is fine, but even those who prioritize individual selection agree that selection occurs on multiple levels. To really proceed with any discussion you need to clarify how exactly the selection occurs and what the relation between the levels are in the real world. Too often critics of "orthodox" population genetics play the game of critique without generating much in terms of a counter-system. The beauty of population genetics is that its relatively simple formalism does make it easy to critique; some of the algebra and other mathematical methods can be a bit hard to follow, but ultimately all that's needed is time & effort. No hermeneutical analysis of cryptic texts is needed. I don't think one can say the same for the arch-anti-adaptationist, Stephen Jay Gould, who liked to deal in words. One might wonder as to the clarity of someone so often misunderstood. Finally, in the comments Bora states:

Coyne is a knee-jerk anti-Gouldian and he will use any opportunity to slander Gould, appropriate or not. And I am not an adaptationist myself, but the questions of the origin of diversity and the origin of adaptation are central questions of Biology which can partly, but only partly, be explained at the level of the genes.

First, I doubt as a geneticist such as Jerry Coyne spends much time thinking about Steve Gould's ideas much. Second, I just checked Speciation (use search inside on Amazon) and I don't see a strong anti-Gouldian ax grinding. There's some skepticism, but we're not talking about Darwin's Dangerous Idea here. Finally, I think it might be relevant to point out that from what I recall Jerry Coyne comes out of Dick Lewontin's lab at Harvard, and Lewontin was long a collaborator with Gould (e.g., spandrels). So I am wondering why Bora claims Coyne is an "anti-Gouldian"? In this thread and over at Greg's Bora has mentioned that this sort of controversy is going to be great for traffic. All for the good, but controversy should be grounded in accurate representations of the arguments. Jerry Coyne an "anti-Gouldian"? Population genetics just an embellishment of the Hardy-Weinberg equilibrium? Come on. Many of the readers of ScieneBlogs don't know much about population genetics or Jerry Coyne, and comments by ScienceBloggers carry some weight and authority. Can we be a little cautious and sacrifice rhetorical positioning for the sake of some fidelity to reality? I do believe that in the end Truth will win out, but cutting out the noise can help in reducing the time until resolution.

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