Definition of Evolution

RAZD wrote: Yes, it works for me, too. But the evo-devo people say evolution can happen even without the inheritance of genetic traits. Lamarck would have agreed. But I don't.My own short definition of "this evolution thing" is simply: A population's success in fixing beneficial alleles. This definition goes a critical step beyond saying only that evolution is a "Change in a population's genetic traits across generations."First Law : Second Law :: change in genetic traits : fixation of beneficial alleles”HM

WK: I have read Mary Jane West-Eberhard's entire "Developmental Plasticity and Evolution" (2003). She is a leading evo-devo-ist, and she argues for the role of "homoplasy" as an alternative to homology (genetic inheritance) for explaining evolution. She argues for a "homeostatic, canalizing, contraining force" coming from the environment that accounts for evolution. Well, who would deny that changes in environmental conditions will provoke adaptive responses by populations, but adaptation does not occur until the benefical alleles are fixed. That is where evolution happens, IMO.The same criticism can be leveled at another evo-devo-ist, Simon Conway Morris, who, in his "Life's Solution/Inevitable Humans in a Lonely Universe," says:

quote:

---

So the beetle, no longer the butt of Haldane's jibe, is an example of the richness of a Creation...None of it presupposes, let alone proves, the existence of God, but all is congruent. For some it will remain as the pointless activity of the Blind Watchmaker...

---

Is there any doubt who he has in mind for this barb?Then you ask: I don't see evo-devo-ists talking about methylation or introns or other factors relavant to evolution. But what if they did? Even those are members of a genetic complex that must be heritable or otherwise lost in a population”HM

Nosy wrote: I agree that selection is not the only way that alleles get fixed. Drift will fixed them, too. And whatever is beneficial will likely play its role when selective pressures arise.”HM

WK wrote: Yes, I do agree, it is not specifically about genetic heritability. But Gould is to blame for my reckless use of the term, as in his "deep homology." Consider what he says in "The Structure of Evolutuionary Theory" (2002, p. 82) he says:

quote:

---

Lankaster wanted to contrast homology of overt structure, or homology sensu stricto with homology of underlying generators (later called parallelism) building the same structure in two separate lineages (homoplasy, or homology sensu lato, in Lankaster's terms). Because parallelism could not be cashed out in operational terms (as science had no way, until our current revolution in evo-devo, to characterize, or even to recognize these underlying generators, proper conceptual distinctions between parallelism and convergence have generally not been made...

---

I'm not sold on convergence, but I can see Gould's deep homology, or parallelism, all right. Homoplasy, too, has legs, I quess, but I disagree with the evo-devo's nagging admonition that genes are not essentially and often selfishly in control of adaptation. That's all. Read her. I can find issues with almost every page. Read Morris, too, and tell me he isn't grinding an ID axe. OK. Educated me. What is there in "development" that accomplishes the essentials of heritability? Because no embryo can escape its gametic origin (most of the time). It's a generational thing, isn't it? How do two gametes carry any more information into fertilization than genetic information (save whatever little information comes from their cytoplasm)? I've always wanted to know how "developmental information" evades or escapes its genetic limitations, as Lewontin argues in his "The Triple Helix." He's just spitting back at Dawkins for kicking his colleague's behind”Gould's, specifically.Oh, btw, I come with no guarantee of satisfaction. I'm mostly just winging it, you know...and, boy, are my arms getting tired!”HM

Dr Adequate wrote: Just curious, Dr A, do you know of any evolution going on without the inheriitance of genetic traits. Some people on this forum have claimed there are "traits" that are not heritable. I have agued that a "trait" must be heritable or it is not a "trait." Otherwise, you'd have to explain the three-legged-dog "trait."”HM

RAZD asks: Yes, I am. If you will notice in Message 129 I wrote: ”HM

WK snorts: Smearing shit is not something I really care to do. But in your case... How's that again?”HM

RAZD, you wrote: Michael Whitlock and his colleagues at UBC have done this rather nicely in stochastic terms. I especially like these articles: The Probability of Fixation in Populations of Changing Size and Fixation Probability of Time in Subdivided Populations.Whitlock advances a stochastic model to define the probability of fixing new beneficial alleles:2hs(1-F_ST)N_e / N_tot“ . where hs is the change in fitness of heterozygotes relative to the ancestral homozygote, F_ST is a weighted version of Wright’s measure of population subdivision, and N_e and N_tot are the effective and census sizes, respectively.”So he uses this ratio to define and measure "beneficial."”HM

OK, good point. I was speaking of adaptive evolution. I also recognize drift, gene flow, and sexual selection as means of non-adaptive evolution. You are looking for a more generalized definition, I suppose. I see your point here. Good argument. Then you don't have adaptation per se, you have exaptation, which is Gould's way of explaining how previously fixed alleles that were once neutral, or even deleterious, become usefully adaptive.”HM

Well, no, not "just totally." Where did you pick up the Valley Girl speak in Dundee, Scotland? I liken the Discovery Institute to a Christian organization out to discover nothing but evidence of God and His glory. Ah, what was your point again?”HM

After kicking a few tires, I think I'm ready to buy your yellow jalopy, RAZD.Good thread.”HM