Is there more than one definition of natural selection?

Only if you want to just start making stuff up. Roberta Millstein is a she. As to what she is saying you seem to have understood some of her conclusions but decided to frame in exactly the opposite way to how she presents them.Rather than saying there are situations where Natural selection and Drift are indistinguishable she is arguing against the position that they are always indistinguishable.AS you say the key criteria is whether one considers NS a process or an outcome, but this is a distinct question to whether it is a cause or an effect.I only think of NS in terms of being a process rather than an outcome but I think of it as both a cause and an effect in different contexts. The outcome would only be the way we try to measure the extent to which the process of NS was operating on the population.TTFN,WK

WK, I should have taken more time with Roberta Millstein’s paper”too hasty in getting back to you, I guess, but spring sailing has distracted me. I mentioned just one aspect of her paper that I happen to think is important, and that we haven’t yet discussed enough. So I hurried on from there.I found her paper interesting and relevant to our discussion. She takes issue with J. Beatty’s contention that it is conceptually difficult to distinguish NS from drift:

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Again, in Beatty’s account, natural selection is discriminate sampling, or sampling with regard to fitness differences, whereas random drift is indiscriminate sampling, or sampling without regard to fitness . Yet Beatty maintains that these concepts are not conceptually different . However, there are other possible responses to the problem that Beatty raises. For example, Shanahan (1992) argues conceptually random drift and natural selection are the ends of a continuum.

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She goes on with a rigorous discussion of the concepts, making good points about the differentiation of discriminate from indiscriminate sampling (NS v. drift). She believes, as I do, that they are conceptually distinct. I enjoyed the paper and learned from it. Thanks.Picking up on this concept that views NS and drift as “the ends of a continuum””in others words the “outcome,” and we’re right back to the process v. outcome controversy.I also wonder also about “co-processing” "counter-processing."Assuming they are distinguishable from one another, the five categorical causes of the “outcome” we perceive to be microevolution are: 1) differential reproductive success, 2) random genetic drift, 3) mutation, 4) gene flow, and 5) preferential mating. I view them as processes rather than results, but one process might work on,with, or aganist another. The outcome ultimately must mean that a new allele-frequency equilibrium is established after certain formative processes have taken place. I would call this “microevolution.” But microevolution is not likely to be caused by only one of the known causes. They probably work in combination, which doesn’t make them any easier to differentiate.And maybe there is even “counter-processing.” I take notice in Essential Genetics/A Genomics Perspective (2002, p.523) that Daniel Hartl and Elizabeth Jones conclude:

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It is apparent from [their studies] that selection tends to eliminate harmful alleles from a population. How, harmful alleles can never be eliminated totally because recurrent mutation of the normal allele continually creates new harmful alleles. These new mutations tend to replenish harmful alleles eliminated by selection. Eventually the population will attain a state of equilibrium in which the new mutations exactly balance the selective eliminations .

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How do they define “selection”?

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selection In evolution, intrinsic differences in the ability of genotypes to survive and reproduce; in plant and animal breeding, the choosing of organisms with certain phenotypes to be parents of the next generation; in mutation studies, a procedure designed in such a way that only a desired type of cell can survive, as in selection for resistance to an antibiotic.

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And how about “natural selection”?

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natural selection The process of evolutionary adaptation in which the genotypes genetically best suited to survive and reproduce in a particular environment give rise to a disproportionate share of the offspring and so gradually increase in the overall ability of the population to survive and reproduce in that environment.

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So, by their definition, NS is a process, or maybe an amalgamation of co-processes and counter-processes.Regarding Hartl’s (and others’) experimental work to test the accuracy of predictive models of random genetic drift, it’s worth posting here one graphic representation of this effort: “Figure 14.27 (A) Random genetic drift in 107 experimental populations of
Drosophila melanogaster, each consisting of 8 females and 8 males.
(B) Theoretical expectation of the same situation, calculated from binomial
distribution.” (scanned and quoted from p. 528, Hartl & Jones, 2002)So, at least experimentally in very small populations, drift can be both modeled as a process and calculated as a result. But, in nature, I doubt if the “continuum” would end there.”HMEdited by Hoot Mon, : No reason given.

I'm actually saying something simpler. Simplicity is a theme that runs throughout my participation in the creation/evolution debate. If I really had to make clear subtle distinctions in order to successfully describe natural selection to someone just embarking on understanding the concept, then I'd feel I'd set myself an impossible task. I think it's important to take into account the level of understanding of the intended audience. So, no, I wasn't alluding to chance events or anything like that in my reply to Hoot Mon or to you.I had never watched Cosmos, so I'm gradually working my way through it. Today I completed episode 2 where Sagan talks about evolution. His presentation shadowed Darwin's, first explaining artificial selection, then using it to introduce natural selection. His presentation was something anyone could understand, and I think natural selection has to be understood at this level before launching into more detail. I still feel like we've skipped over the simple into the complex before the simple has been understood by everyone participating in this thread.I would never challenge a Futuyma definition, but I don't want to consider things at that level of detail. I was actually only trying to make a much simpler point. Plot differential reproductive success over time: Differential reproductive success is the y-axis and it doesn't matter what the units are, time is the x-axis. All I'm saying is that at the point in time where the line crosses the x-axis, natural selection is not suddenly absent. Differential reproductive success might be 0, the result of the selection pressures might all end up at the same equal outcomes, but the process of selection is still ongoing. The winter storms still happened, the summer drought still happened, the predators were still there, mates were still finicky, and the end result of it all for that generation was a differential reproductive success of 0, but the process of natural selection was still active. It doesn't suddenly cease at the crosspoints.For someone still trying to grasp the concept of natural selection, I think describing it as turning on and off as a function of whether differential reproductive success is zero contains a high potential for confusion. I think even mentioning differential reproductive success before getting the essence of the concept of natural selection across contains a high potential for confusion. Maybe it's just me, but this thread and the previous thread seem like prime evidence of this. I'm not blaming you or anyone else, I just wish we could all get on the same page. I know we're being pressured to discuss details because they're being introduced in other messages, but I don't see how repeating the approach of the previous thread could result in a different outcome.So for me it comes down to getting across this simple point, the same one that Darwin made: artificial selection is what breeders do, deciding which individuals get to contribute progeny to the next generation. Natural selection is what nature does, deciding through the effects of the environment which individuals get to contribute progeny to the next generation. Anyone who doesn't understand natural selection on this level is not going to understand it on a deeper level, no matter how many messages of explanation are posted.--Percy

Hi Percy,I fully concur with your desire to explain things in the simplest possible way before jumping into details - the old walk before you run concept. That is, in fact, the point of the marble analogy - a simpler explanation of what happens in NS I have never encountered. However, I think you've actually introduced more - and unnecessary - complexity with your fitness 0 discussion, as well as lumping chance under NS. Finally, I'm not sure where you derived your graph, but the only thing I can recognize in what you're graphing is possibly a population-level response to cyclic ecological change. It certainly doesn't appear to have any bearing on fitness, or NS (beyond the cyclic nature of some types of selection pressures). It certainly doesn't represent what happens in "differential reproductive success over time" that I can see. I agree with your first sentence. So I have to ask: Why are you doing precisely that? Isn't that exactly what first your re-wording of the marble analogy and now this weird graph is intended to convey? That fitness can be 0? If I'm confused on this, I would be willing to bet others are as well. Obviously, I'm not understanding you at all.From your message 24 on this thread:

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And so in my version of your marble example I referred only to selection, not natural selection, and it was intended to be analogous to only a single generation. Even though the marbles had identical phenotypes with respect to size, that is no guarantee that the next generation would all be the same size. The marble drop represents the selection part of the process, not the reproduction part.

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NS operates on each generation independently, although the outcomes of NS - adaptive response being one example - can only be seen after multiple generations. You are vastly overcomplicating what happens by claiming that selection - and I'm unclear what the distinction you're making between "selection" and "natural selection" actually amounts to - doesn't affect changes from one generation to another. This would be an extraordinarily special case. Further:

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In the next generation some of the marbles may be of different sizes. Since selection pressures are operating in each generation, sometimes choosing more, sometimes less, sometimes all, sometimes none (extinction), the process of natural selection is going on. The fact that in one generation every marble survived doesn't mean natural selection suddenly stopped or was absent.

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No one has EVER said this. In fact, near as I can make out, you were the one to introduce this idea. Regardless of your perspective on the gene/individual/whatever debate, NS is constant although the exact composition of the selection pressures is highly variant - leading, ultimately, to changes in the relative contribution of organisms with different phenotypes/genotypes/alleles/whatevers to future generations. This is NS, and it don't get any simpler.With ref to NS vs AS, I'm not sure why you brought it up. It's never (to my knowledge) been a point of disagreement between us. You had some quibbling with Mod in the other thread, but you and I certainly didn't differ on the definitions.If you're interested in simplifying things, I'm all for it. However, please be careful how you go about doing that, as there is potential to lose meaning at the same time.

I agree with a lot of what you say here, since it is you talking about a paper I already said I agreed with .I would take issue with one thing however. Why do you still insist on saying that preferential mating (Sexual selection) is separate from differential reproductive success (Natural selection). You can certainly have NS without sexual selection but unless you are talking about a meaningless case of preferential mating based on non-heritable traits I don't see how preferential mating can be anything other than directly connected to differentials in reproductive success.Why do you persist in trying to separate sexual selection from natural selection?TTFN,WKP.S. There are some quite nice simple simulations of a number of relevant things at the site EvoTutor . You will need Java runtime installed to view the simulations.Edited by Wounded King, : No reason given.

I do like this argument over sexual selection = natural selection (or permutations thereof). I'm sticking with my side: they are not necessarily an equality. I'll give you this much: nonrandom mating could work as a co-process along with natural selection; it may even work against it as a counter-process (as I discussed in Message 32).I'm, finding less time these days to stay in these discussions. They keep getting deeper all the time. And that's good. But, oh, the commitment...”HM

Because every time we have the conversation, he forgets it after a few days.

I was heading off to bed when I saw this, so I'm just going to write a few sentences.Unless I'm reading your tone wrong, you seem somewhat peeved at me. As I stated in my first reply to you, I've been seeking a consilience. Much of what I've written in this thread is an attempt to incorporate my understanding of what you and Mod are saying into my own thinking. Not to hold myself up as God's gift to comprehension, I have no such conceit, but if I who enthusiastically accept evolution am so wildly off track in understanding what you and Mod are saying, you can just imagine what creationists are getting out of this.About me introducing the 0 differential reproductive success issue, I was responding to Hoot Mon's mention of it. In my message that your reply is addressed to I stated that I didn't think it was an appropriate level of detail, but that we're being pressured into it because others are bringing it up, so I'm puzzled that you think I'm introducing it.My own opinion is that we're doing a just making a terrible hash of describing natural selection. Hopefully none of us believe that we're the only one being perfectly clear.--Percy

I have more time for a reply now. I was originally responding to Hoot Mon's statement that when differential reproductive success equals 0 it means there was no natural selection. I wasn't talking about fitness equalling 0, by which I think you must mean differential fitness equals 0, i.e., that they're equally fit. If so, while it might be interesting to consider things from that point of view, they don't seem like synonyms to me. Not sure why you say this, since you're responding to a message where I say that I'm not saying anything about chance. It's not a derivation of data, it's just an illustration of a simple point. It doesn't really matter to the point I'm making, and this interpretation is fine, except for the cyclic part. The only reason my graph is cyclic is because of the difficulty of creating graphs with characters. So I went up and down once, then copied several times. If I'd been drawing freehand it wouldn't have been so regular, and its cyclic nature has nothing to do with my point. The shape of the graph is unimportant, the periodicity is unimportant. The only thing of significance is that the line crosses the 0-point, i.e., passes through the x-axis. It wasn't intended as capturing an actual situation. It was just an illustration of the fact that differential reproductive success is a time-dependent variable, and given that fact it is inevitable that it will cross the 0-point, the x-axis. The crossings of the x-axis are not points in time where natural selection has ceased to operate. As I said before, there were still winter storms and summer droughts, dangerous predators and finicky mates. The fact that during some seasons two sub-populations have equal success reproductively does not mean there was no natural selection during those seasons. Perhaps it would help if I reintroduced the original claim from Hoot Mon that I replied to and that started this discussion. This is from his Message 10: Does that help? I can elaborate about the discussion that ensued if you like, but it would just be a recapitulation of the messages that led eventually to your first reply to me. If you agree with Hoot Mon's statement then please help me understand why, while if you disagree please help me formulate a proper rebuttal. I'm not sure why you say this. If you take the example of a population of a species that reproduces once a year, then measuring the allele frequency across the gene pool every spring would show changes on an annual basis, which equates to measurable changes due to natural selection after a single generation. I grant the practical difficulties of making such measurements, but that's a separate issue. It's a concession to Modulous, actually. He said more than once and in different ways that natural selection is much more than just selection that is natural. And if you go to Wikipedia and look up selection and natural selection, they do not appear to be synonyms. Any clarity you can bring to this would be welcome.To repeat something I seem to find myself saying a lot, when people understand what is actually going on in the real world, they don't need precisely defined terminology to get their points across. You'll often hear people in technical discussions say things like, "Well, I wouldn't put it in those terms, but I understand what you're saying."But here we have a different problem. We're trying to explain what is going on in the real world by cutting our terminological definitions extremely fine, and when you get to that level of detail you simply won't find agreement. Until natural selection is understood at its simplest level, more detailed levels of understanding are simply not possible. But though we both say we believe this, we still seem helpless to escape these endless digressions involving the detailed definitions of specialized terms. I quoted Hoot Mon saying this just above. Is that why we're doing this, because you think I'm rebutting a point no one ever made? I can't figure out what the problem is, because you go on to say: Which, of course, I agree with. I was just trying to be thorough in describing where I was coming from and what definition I think is appropriate for the introductory level. I wasn't trying to tell you something I thought you didn't know. I naturally regret any contribution I've made to the confusion, but please don't mistake a venture in the wrong direction as reflecting insufficient concern, because a misstep is a possibility we're all vulnerable to.--Percy

No one has said they are an equality, we have persistently said that sexual selection is a subset of natural selection. It is one of the many 'environmental' factors which can form a selective pressure for a population. How? It is obvious how migration into a population, mutation and genetic drift can act as countervailing processes, but how do you propose sexual selection does so. There are lots of selective pressures that can pull/push in different directions but they are all incorporated into NS so how can selective pressures be counter to NS itself?TTFN,WK

With your permission, I'll lump the two responses into one, here. I am not peeved. I am honestly confused over what you're saying. I don't want to get into a "who said what to whom" digression here, so I'll just address what I think are the main areas I don't "get".1. The graph is really throwing me. Beyond the mechanics of drawing a graph on EvCForum (an explanation for which would unfortunately be wasted on me given how technologically challenged I am at best), I literally can't comprehend what you are trying to show. Assuming we are using the same definition of fitness (i.e., {avg. fecundity} X {% progeny surviving to reproduce in the F1}), I don't see how the graph represents this. The only synonym I can envision for "zero fitness" under that definition is "extinct" - i.e., either the organism didn't reproduce (zero avg. fecundity), or none of the progeny survived to reproduce (zero % survival). Moreover, I am having a difficult time wrapping my brain around the idea of "negative fitness" in this context. How does a fitness function become negative? Apologies in advance for the reductio ad absurdum, but when I tried to figure out what you meant the first image that popped into my head was someone going back in a time machine and killing the organism's ancestors (I've probably read too much science fiction). It's fine if you are using a different metric for fitness, but you need to explain what you're using (or maybe explain what it is you're actually trying to illustrate if it isn't fitness), 'cause otherwise the graph doesn't make sense to me.2. Okay, I think I'm beginning to catch a glimmer of what is going on - and where my confusion seems to arise. You and I tend to regard NS as a process, whereas Hoot is thinking of it as an outcome. Differential reproductive success is indeed an outcome of NS, and from that viewpoint Hoot isn't wrong in what he wrote. I don’t agree with him that this is necessarily a good way of looking at NS in isolation, however. It is sort of like the genecentrist inability to separate “selection” from “evolutionary response to selection”. It doesn’t mean the viewpoint is invalid, it just means that they’re not making as fine a cut as others are.Perhaps I can contribute some simplified, short “definitions” that might clarify (or potentially confuse things further):1. environmental selection pressures: The biotic and abiotic factors that impact an individual organism or population of organisms during their lifetimes. Selection pressures operate continuously, but are variable in their effects, strength, and nature.2. natural selection: The process, based on environmental selection pressures, that filters genotypes/phenotypes in the wild. Depending on the relative strengths of these selection pressures, the outcome of natural selection may influence the relative contribution of these genotypes to future generations. It may increase, decrease or stabilize the proportional representation of a particular genotype in the population.3. adaptive response (evolution): The long-term permanent change in the relative proportion of alleles or genotypes in a population in response to natural selection.I don’t know if that does any good, or merely obfuscates things further. One possible suggestion - don’t try and directly respond to someone’s misconceptions (Hoot, in your case). Rather, try and develop a working and concensus definition of natural selection (if that’s your goal). And THEN address the misconceptions in that context.Edited by Quetzal, : edited out redundant sentenceEdited by Quetzal, : clarity

I will pick up on this notion of co-process v. counter-process, as I discussed in Message 32. I’ll argue that natural selection is a process, along with all the other processes, including sexual selection.I don”t see why sexual selection (or nonrandom mating) needs to be only imbedded in natural selection as one of its relegated features. But I do see how a causal continuum needs to be considered. I’ll take the position that any or all five known microevolutionary causal processes, co-mingling in that continuum, can make a microevolutionary event happen. This may be the most realistic point of view. As Hartl and Jones (2002, see Message 32) have already concluded, mutations may affect natural selection either by enhancing or suppressing it. I could see similar effects”enhancement or suppression of NS”from the other three causal processes attending microevolution, including nonrandom mating. I single out nonrandom mating here because, in and of itself, the process refers only to one way an HW equilibrium can be disturbed.How could sexual selection, as a process, suppress natural selection?If natural selection”which by definition is the ”differential reproductive success amongst individuals of a population’”selected for trait (characteristic) X, it is also possible that, by my reasoning, nonrandom mating could select neutrally or against trait X. Yes, I’ll agree that in either case NS may be affected by the causal process we call sexual selection, but if nonrandom mating somehow suppressed NS enough to neutralizing it, I would have to conclude that sexual selection could be a counter-process as well as a co-process.Sorry, I don’t have any examples. But try this: Imagine a population wherein the good-looking ones mated exclusively with each other (by virtue of traits), but they didn’t reproduce as much (per capita) as the bad-looking ones, who had to settle for other bad-looking ones, but who were coincidentally more fecund. If I put this on a sliding scale, I could envision sexual selection swamping out NS altogether.Why not?”HM

Can you see how a causal continuum sufficiently correlates whatever effect sexual selection propertizes?The nature of the continuum of NS is usually displaced by notions of historicity instead with an improper philosophy of contingency. That seems to bridge your two sentences without me necessarily invoking Russell's use contra Leibniz of

I agree with all your definitions. It's the same way I would define those terms.In this thread I've been trying to express things in such a way that when I say something like, "When during a harsh winter one rabbit survives and another dies, that is natural selection," that Modulous doesn't object and say that it isn't, that natural selection is much more than just selection that is natural, because that led us to a big digression. And so I changed the way I expressed things in order to keep the focus on Hoot Mon's questions and not get into digressions, but that still caused digressions, this time with you. Is there a way for me to express things that both you and Modulous can agree with?Addressing specifics, about the graph, the y-axis isn't fitness, it's differential reproductive success. Whenever you calculate a difference, no matter how conceptual and difficult to measure something might be in reality, unless one quantity is always constrained to be greater than another, negative values are possible. Like you I don't know what negative fitness is, but the y-axis isn't fitness.I'm having trouble parsing this: You say that Hoot Mon thinks of NS as an outcome of differential reproductive success, then follow by saying that Hoot Mon isn't wrong to think that differential reproductive success is an outcome of NS, which is the exact opposite. Perhaps you can rephrase.Maybe I'll change my mind when I finally understand what you're saying, but I cannot at this time see how a differential reproductive success of 0 is always the equivalent of no natural selection taking place. For example, imagine two subpopulations which produce equal numbers of offspring, but that during that particular reproductive season leading up to the equal numbers of offspring that many eggs in both subpopulations were eaten by predators. That's natural selection, even though the differential reproductive success was 0.Futuyma's definition is I think trying to lay the foundation for a rigorous mathematical approach where specific traits are considered. Thus it makes sense to say that with respect to trait X there was no natural selection of X because there was a differential reproductive success of 0 with respect to X. That is indeed a possibility when considering single traits or small collections of traits. The requirements of a quantifiable approach require this. But we can't ignore the reality that during this period when there were supposedly no natural selection pressures with respect to X that many organisms possessing the trait were living and dying, mating and failing to mate. That's selection at work. And this is where I think you introduce the idea that chance selection with respect to X is not natural selection, which seems like a terminology preference that while perhaps widespread in the industry is not dominant? I don't know for sure, but it feels that way given all the reading and debating I've done about evolution without ever encountering this confusion before.--Percy

What do you expect from a geezer?btw: Is that all you have to say about drift v. selection?”HM .