Darwinism and Nazism

Hi Syamasu,You've brought up my agreement with you on some issue several times in this thread. I vaguely remember it, but could you provide the context again? I don't remember any discussion on photosynthesis, for example.As to NS operating on a clonal population, I think both John and I were agreeing with the idea only in the trivial sense that a clonal lineage without variation subjected to environmental stress (natural selection) would be eliminated. Only if there was some variation in the population would there be any survivors. Actually, I can't think of any extant wild population where this is the case. Only in pure laboratory strains kept under very controlled conditions would you find completely homogenous populations.OTOH, there is a distinct linkage between variation among individuals in a population and evolution. Remember: selection operates at the level of the individual, evolution at the level of the population/species/lineage. Selection in the sense of environmental factors CAN operate in the absence of variation, evolution cannot. Works for clones as well. (Note: this might be a bit simplistic: apparently Dr. Caporale's book, "Darwin in the Genome", makes a good argument for the operation of ns at the genome level. If so, she's one of the first to demonstrate an actual mechanism for gene selection - the absence of which has been the basis of my disagreement with the gene selectionists all along. Unfortunately, although I had an opportunity to purchase Dr. Caporale's book during my last bookstore raid, it came down to a choice between her book and Jared Diamond's new book on cultural evolution. Being the illiterate ecologist that I am, I bought Diamond's book. Seems I was a bit hasty. )

Hi Syamasu,

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I'm sorry, you don't agree then with the usage of selection in the photosynthesis example? I think it would be better for discussion if people state their opinions with argument. It's possible I've mistaken your position, I certainly won't insist on what your position is if you tell me it is otherwise.

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Actually, I'm not agreeing OR disagreeing with the photosynthesis example, because I don't remember (I've been out of contact for a month) what the example was. Would you mind stating it again or perhaps noting which post # it was? Then we can talk about whether or not I concur. Sorry for the faulty memory...

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Are you saying that the use of Natural Selection on a clonal population is only valid in respect to another population which does have variation?

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Nope. NS can operate on a clonal population without variation. Evolution, on the other hand, cannot operate without variation. Let me explain: theoretically you could have a homogenous population of clones - call 'em type AA for the sake of argument - quite happily reproducing AA's ad infinitum as long as the environment is conducive to the survival and reproduction of type AA's. Even if some variation arises through mutation, it may not be viable. If something in the environment changes, it is quite possible that the environment will no longer support AA's. If this happens, natural selection wipes out all the AA's and the population goes extinct. This is what I meant when I talked about NS operating on a clonal population. If no environmental factor changes, natural selection doesn't happen. Nor does evolution. If something changes, natural selection takes its course. If, on the other hand, the change occurs while there is still some mutant - an AB, for instance - in the population, the mutant MIGHT survive. In which case, you now have a clonal population happily reproducing AB's, but the AA's are long gone. In a nutshell, it can be said in this case that the original AA population has evolved into an AB population.Edited to add: I want to emphasize that the above is an entirely theoreticali] construct - a thought experiment if you will. I can't think of any actual population outside a lab where this could possibly occur. Every "wild" population that I'm aware of - whether clonal or not - contains some degree of variants.Edited again to add: Now that I read the above over, I realize that even in the theoretical case noted above, natural selection (in the form of stabilizing selection) is what would eliminate the non-viable AB mutant in the first example. The only way you could postulate the absence of natural selection in a clonal population would be if each clone perfectly reproduced itself with no errors. I guess you just can't get away from NS in one form or another.

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Do you agree that selection describes the relation of an organism to it's environment in regards to the event of it's reproduction?

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Not entirely. The relation of an organism to its environment is better described through the concept of marginal fitness. Selection describes the action of environmental factors (which includes everything from climate to symbionts to competitors, etc) on the individual organism. Natural selection, at least as I understand the concept, corresponds to the action of these factors, rather than a relationship as you noted. The results of this action may have an implication for the chances of reproduction, reproductive efficiency, survival, food collection, etc etc, all of which are bound up in the concept of fitness.[This message has been edited by Quetzal, 01-20-2003][This message has been edited by Quetzal, 01-20-2003]

Hi Syamasu,

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For example: light (environment) falls on the photosynthetic cells of a plant (organism) which contributes to it's reproduction (positive selection).

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I have to disagree with this statement. Photosynthesis has no direct relationship to either selection or reproduction. Photosynthesis is simply the use of light energy by a plant to synthesize organic molecules. It's the light-powered chemical factory of the plant. The molecules produced are then used to create the structures necessary for reproduction for instance, like pollen, reproductive organs, seeds, etc, as well as all the other necessities for growth and life. Heterotrophs, on the other hand, use the already stored energy produced by plants through photosynthesis to power their own systems.Secondly, "positive selection", by which I assume you mean directional selection, refers to the elimination of variants at one or the other end of the mean frequency distribution in a population, and has nothing whatsoever to do with an individual organism's survival OR reproduction (unless, in the trivial sense, we refer to one of the eliminated individuals).

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I'm not sure how or if, you are invalidating this usage with your reference to marginal fitness. In any case you previously said that selection is just about surviving or not surviving. It is hard for me to understand if that is true, then why selection is not commonly defined that way.

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Actually, I think selection IS commonly defined this way. Selection relates to the pressures effecting the survival of an individual. Marginal fitness refers to the relationship between an organism and its environment.

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NS is now commonly defined as differential reproductive success of variants. This formulation is inapplicable where variation is not relevant, such as with endangered species, or with the photosynthesis example.

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I don't agree - natural selection IS NOT defined as "differential reproductive success of variants". Evolution might be described this way (although it would be an odd way of putting it), not selection itself. But again, evolution is only applicable to populations, not individuals.As to endangered species - organisms are endangered primarily because of the action of natural selection. "Endangered" classification is a result of changes in the environment (selection pressures) in which the population lives.

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It also, quite rightly IMO, doesn't talk about survival at all as you do. Survival selection, and reproduction selection are two distinct theories, where survival selection strictly speaking, is inapplicabe to evolution theory, except if we begin to talk about evolution within the lifespan of an individual.

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And herein lies the rub. Of course we're not going to talk about evolution within the lifespan of an individual - individuals don't evolve. Survival and reproduction are two faces of the same fitness coin: differential mortality and differential fecundity. Certain phenotypes are better able to survive AND/OR certain phenotypes contribute disproportionately to subsequent generations. This is the foundation of population genetics, which in turn is the foundation of evolutionary theory. As gene frequencies in a population change over generations through the action of natural selection (the elimination of negative variants OR promotion of positive variants) - whether through differential survival or differential fecundity - the population is said to be evolving. Stasis - where distribution frequencies remain fairly constant within a population (or better said, vary around a mean) - is the result of stabilizing selection which has the net effect of preventing evolution from occurring by eliminating the variants from both ends of the mean!Out of curiosity, how does your "general theory of reproduction" account for evolutionary stasis?[This message has been edited by Quetzal, 01-21-2003]

Percy,I think you've hit the nail on the head. I would like to clarify a bit, however.

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...I think you may have missed something in Quetzal's perspective because it definitely makes a difference whether an organism is "deselected" before or after it's had a chance to reproduce...

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You are absolutely correct. I think part of the misunderstanding arises from my attempts to decouple the explanation of natural selection from its ultimate effect: evolution of a population or lineage. Syamasu began by arguing against natural selection - not evolution. I've been trying to show that natural selection is a mechanism or process that leads (along with drift) to changes in the frequency distribution of traits within a population (i.e., evolution). It can be understood both from the standpoint of differential mortality OR differential reproductive success/fecundity, or even both together. I think that's how we got side-tracked onto the clone bit. In any event, since evolution depends on inheritance, any organism that doesn't reproduce, no matter how well "adapted" to its environment, doesn't contribute to the evolution of its population. You can have the most amazing butterfly with the most perfect genome on the planet, but if it gets eaten before it reproduces, it's an evolutionary dead end - and hence isn't "fit" by the standards of evolutionary biology.Syamasu's main problem with the idea seems to be that natural selection (in most of the details), is inherently a negative process: it weeds out rather than builds. For him, from what I've been able to discern, couching evolution in terms of reproduction removes the "negative" connotations and the "negative" implications (e.g., social darwinism). His "reproduction or no reproduction" construction isn't all that bad - it's basically the same thing everyone else is saying, just different wording. Unfortunately, he has taken it too far, and denies all of the messy bits: no inter- or intra-specific competition, etc, and he seems to have some difficulty understanding that the "environment" that effects an organism's chances of reproduction INCLUDES all the messy parts - including competitors. He also seems to have some problems separating primary, secondary, and tertiary causes (c.f., the light effects reproduction through photosynthesis bit).I'm really not sure at this point what we can do to clear things up.

Hi Syamasu,

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In my own experience, the relation to Social Darwinism comes from comparing organisms, using words like good and bad. Also the term success or struggle, which posits reproduction, or survival as a worthy goal.

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Actually, I agree with you. The social darwinists, eugenecists, monists, and others of that ilk did base their philosophies on value judgements. They took the conceptual framework of "evolution = change driven by selection" and imputed subjective values to the nature of that change. This is the fundamental fallacy in social darwinism. The reality is, of course, that evolution, whether of species lineages or societies, says nothing whatsoever about relative worth. Nor does it say or imply anything of "purpose" or "goals" (which, in my opinion, is a vestige from relgion or metaphysics). However, to reiterate, the fact that the social darwinists distorted an elegant and well-supported concept to suit their own predispositions and agendae doesn't invalidate the original concept - merely their distortion. And that, I think, is where most of us have a problem with your argument: we feel that the formula "variation + ns and drift + inheritance = evolution" doesn't axiomatically require or imply direction, purpose, or value. And note well that the formula can be restated many different ways, and NONE require these.On the other hand, it is a convenient "short hand" to speak in comparative terms like "better adapted" or "more fit" when discussing the action (or better said, results) of natural selection. However, the comparatives should not be taken to mean "of more value". "Fitter", for instance, as used by biologists is simply an easy way of saying "has a higher probability of replicating its genotype in the particular environment in which the organism (or population) lives in comparison to other individuals or populations in the same environment and subject to the same conditions". Whew! "Fitter" is better...

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It should be clear now to everyone that the popular formulation of Natural Selection is biased towards evolution, which formulation unfortunately unusable for describing endangered species.

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Again, I agree about the first part - the concept of NS is biased towards evolution. It is, after all, one of the primary engines of evolution. It is the iterative and creative power of NS that drives evolution and diversity, so saying it is biased toward evolution is certainly correct.I'm not sure why NS would not be useable for describing endangered species. As I noted in a previous post, NS is the mainly the proximate cause of species endangerment in the first place. Perhaps you could expand on your statement and explain in detail what you mean? Possibly using an example from an actual endangered species for illustration? Apologies - as an ecologist, I think better when I have a concrete example to look at/think about. I'm honestly not clear what you mean.

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Also, there are other possible adaptive evolutionary scenario's which fall outside differential reproductive success of variants. Mainly the extent to which a mutant organism inhabits a different environment then it's ancestor falls outside the standard formulation. So there is again bias in the formulation there, this time towards those evolution scenario's that present a limited set of shared resources between variants, in stead of partly shared, or not shared resources.

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Again, I'm not really sure I'm following you here. It appears at first glance that this IS the standard formulation. In allopatric speciation, for instance, either the ancestral population is divided by some barrier, and the "daughter" populations diverge from both the ancestor and each other, or a peripheral isolate diverges from the ancestor which continues to diverge while the ancestor remains relatively unchanged. They don't even have to be physically isolated by a geographic barrier - it may be behavioral, reproductive, etc or some combination.If the environment changes, one or another variant may be "favored" or survive, while the other goes extinct. Alternatively, one of the variants may be enabled to move into a new habitat. In both cases, you would have a "mutant" organism inhabiting an environment different from its ancestor. This is actually fairly common - and is one of the key observations Darwin himself made.I don't see that there is a bias toward direct intraspecific competition for resources - that is simply one (of many) of the "selection pressures" subsumed under the umbrella of natural selection.If I've misunderstood you, please let me know.

Hi Syamasu,

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It is useless to look at how fast the 3 leaved clover is disappearing compared to the 4 leaved clover in some area. There isn't neccesarily any significant difference between the disappearancerates.

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All other things being equal (no particular adaptive advantage from the standpoint of the four vs three-leaved clover), I'd say it depends on what question you're trying to answer. If you're simply making an observation - there are more four leaved than three leaved clovers in an area today as compared to yesterday, then you're probably right. If, on the other hand, you want to look at the "why" a phenomenon like this is occuring, then you would have to consider various environmental (i.e., selection) factors. Ecologists and conservation biologists do this all the time.

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It's generally useless to look at variation when looking at endangered species, except in a way that runs counter to the logic of differential reproductive succes of variants. Apparently there should be some minimum variation for long term reproductionstability.

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Of course the basic formulation of Natural Selection still applies to endangered species, because it doesn't require variation.

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Weeell, yes and no. If I were trying to preserve a species or population, I'd want to look and see whether there were any variants that were more viable. With a highly homogenous endangered population, I'd want to experiment and see if outcrossing could increase their survivability. There are a whole pile of different things to consider with endangered populations. It again depends on what question you're trying to answer. I agree that variability is usually a good thing (in the long run) in a population. A small, genetically homogenous population (whether sexually reproducing or clonal/hermaphrodite) can often be at greater risk of extinction than a variable population. On the other hand, variation can be a bad thing if it means lower overall fitness and/or increased mutational load. Nature is often a trade-off.

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Darwin and Wallace both got their idea for origin of species, from Malthus. The idea is based on competition for limited resources. There are just a few resources, a mutant who has an "advantage", will replace the ancestor variant, like that. It doesn't deal with scenario's from the perspective that there are large amounts of oppurtunities for reproduction, if only a mutation occured which corresponds to the niche.

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Well, Darwin certainly read Malthus (I don't know about Wallace). However, he pretty much had his theory down before that (population variation + descent with modification + differential extinction). It was the mechanism he was missing until he read Malthus's treatise on population dynamics and competition in human societies. It provided one of the final pieces to the puzzle - how it happens in nature.If there are large amounts of opportunities, the observations that have been made on living populations show that organisms will breed until they fill all available niches - something that can only occur with variation. If a single species, for instance, has no variation and no selective constraints, it will reproduce until it's filled its current niche to carrying capacity, then will go no further (or possibly destroy itself). A variable species on the other hand may be able to radiate into new niches based on the fortuitous possession of some variation. If it doesn't have that variation, it's effectively blocked.

I concur that we probably don't have much more to discuss on this particular topic. However, I reach that conclusion because I think we're still in large measure talking past each other. If you want to state that "differential reproductive success of variants" is not part of the definition of natural selection - semantically I can accept it. Natural selection is a mechanism or process. "Reproductive success" is one way to measure organismal or species/population fitness in relation to their environment. "Variant" represents the different traits within a population that natural selection operates on. I certainly agree that it makes no sense to compare reproductive rates between vastly different species (of elephants and ants for isntance), unless somehow that had a bearing on their survival.The one thing I'd like to bring out (one last time) is this:

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As before the only requirement for origin of species is for a mutation that contributes to reproduction. Your insistence on variation does not make sense to me.

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This is inaccurate - the requirement for origin of species is reproductive isolation. Mutation can be one cause. Geographic isolation followed by genetic divergence can be another. There are other causes. Variation allows for the possibility that a species/population can take advantage of new niches (radiation), survive new pathogens, etc. Whereas I concur that rapid massive environmental dislocation is likely to cause extinction (not always - check out bacteria and drug resistance), some change is gradual enough that populations can adapt. Local populations are disappearing all the time. If a species has a broad enough range, such local extinctions are unimportant. Finally, population pressure is only ONE of a myriad of possible selection pressures.Anyway, interesting conversation. Thanks.

Yeah, I agree. I was being nice by not saying "it is trivially true that...". I DO think that NS is biased toward evolution in the same way 1+1 is biased toward 2. It's one of those statements that is true by definition - but not significant in any sense. Besides, Syamasu seems to like people to agree with him - and when you can on some utter minutiae like this, it doesn't cost anything and keeps the flames and rhetoric down... Look how much effort I put into trying to find some rationale for the bizarre construction "differential reproductive success of variants". [This message has been edited by Quetzal, 01-30-2003]