What exactly is natural selection and precisely where does it occur?

Unless there was some other way of differentiating the marbles (for instance, a sensor that selected for specific light wavelengths - color, or by weight, or something), then there is arguably no selection going on. Once again, we're pushing the illustration beyond what it is intended to convey, unfortunately. Living organisms and their environments are obviously more complex, so trying to stretch the analogy to encompass those complexities isn't going to work. As long as I was able to clarify the analogy (as far as it goes), then that works for me.

You're not being crucified, merely criticized for a large number of persistent misstatements, primarily concerning just two things. I don't know how you managed to skip over the two of them, since they were the sole topic of my Message 217 that you complained about, but here they are again.This one is just a simple contradiction in terms with you claiming there is such a thing as non-selective selection. Here's a sample, but you've said this many times: The other one concerns you're equating of natural selection with evolution. Here's an example: There ya go, have fun!--Percy

Ah, here’s the nub of it:I said upthread: “By definition, natural selection is the possible consequence of uneven reproductive success of individuals in a population.” Modulous agreed.But Percy sees it differently: “I would have said the exact opposite, that differential reproductive success is a possible consequence of natural selection.”Perhaps both points of view are imprecise. After all, isn’t “natural selection” the same thing as “uneven reproductive success amongst individuals in a population.”? One doesn’t cause the other”they are one in the same. Aren’t they?”HM

6 paragraphs and the best you have is a glib rejoinder in one line? After you asked for my thoughts? Would it be possible for you to engage my arguments seriously? That you would suggest that leads me to, again, wonder about your ability to comprehend basic statements in plain English. No, I'm not a gradualist, and if you think what I've said stands in contrast to Gould's views on Punk Eek, you understand neither Gould nor myself. I never said that evolution proceeds at the same constant rate throughout all time, and Gould never said that evolution isn't constantly happening. Are you not able to read statements in plain English? A lot of evidence is accumulating that you are not.

You've asked this before, and I don't think anyone understands why. Of course Crash thinks evolution has causes, everyone does. At the physical level where biology takes place everything has a cause, whether we're able to identify it or not. With regard to what Crash was saying about evolution being an ongoing process, selection pressures of the environs *are* causal factors.--Percy

I have two reasons for saying that:1. Somewhere, I think it may be in Gould's The Structure of Evolutionary Theory, I recall reading a discussion concluding that, by definition, sexual selection is not "selective" in the same sense that natural selection IS "selective." And therefore, in a natural-selection context, it is regarded as non-selective (sorry for no good ref. here). I think the confusion lies in the word "selective." Because it seems clear enough to me that different "selective" things are going on in nonrandom mating vis a vis natural selection.2. Because the Hardy-Weinberg equalibrium of a population specifically requires mating to be random. Thus a change in a population's allele frequencies could be attributed to nonrandom mating alone. Natural selection need not necessarily have played a role in that change of allele frequencies. Taken as it stands, I'll agree with you that this is imprecise thinking (or writing). What I was trying to say is this: If an evolutionary event can be attributed to natural selection then I would say that evolution and natural selection are bound up tightly in a cause-effect relationship. Still, they are not the same thing, and you're right that natural selection does not equal evolution.Score one for Percy.”HM

Hoot, forget Hardy-Weinburg. You'd have a much better case if you could show ONE SINGLE SOLITARY real-world natural sexually-reproducing population where HW is even relevant, let alone descriptive. Don't get wrapped up in theoretical mathematical constructs - it doesn't help the discussion.

Oh, well, I suppose you could say that just about everything worth discussing here is a stretched metaphor of one kind or another. My point is that some people here would argue that the basic act of the marbles falling through the holes is, by way of metaphor, natural selection, whether or not any selection actually goes on. I don't think so, unless I can be convinced that natural selection occurs even where there is no differential reprodcutive succcess amongst individuals of a population.”HM

It is the simplest and most easily understood - I agree.However, Hoot Mon is looking beyond the simple. The natural selection on your diagram doesn't seem to really explain natural selection and its impact on evolution - it just says an animal's life is natural selection. That's about as far away from 'what exactly is natural selection' as we're going to get. I am arguing that there are many kinds of selection. Some of those types of selection are a subset of natural selection, others are nothing to do with natural selection. The individualist tends to look at only a partial list of selective pressures (survival selection, sexual selection etc) so it misses elements of natural selection. Thus the indvidualist perspective is an incomplete description of biological evolution and is thus not a good perspective when answering the question posed in the OP.Survival selection becomes a moot point when we consider individuals that protect other individuals at their own cost. Sexual selection doesn't come into it for genetically intentional infertile individuals (such as with insects). There must be other selective pressures at work! There is a single overarching type of selection which includes all definitions of selection. Since natural selection should only mean one thing - I propose that this 'superselection' should be simply called natural selection.Yes - sometimes survival selection (in the bacteria and antibiotics) is so predominant we can simplify our models just talking about it in those terms. Sometimes we can only describe traits as arising from sexual selection - it is so dominant that all the other effects can safely be ignored (for most purposes).However survival selection ≠ natural selection even though sometimes survival selection ≅ natural selection.There are plenty of times when survival selection is not the big player but kin selection seems predominant. That is when the power of genes comes forwards.Kin selection+sexual selection+survival selection+possibly other selection pressures = natural selection.And natural selection cannot be understood fully in the individual model of survival or sexual selection. Since the topic is about precision and exactitude, the more accurate way of describing natural selection, in totality, is to discuss selection of genetic replicators.Edited by Modulous, : No reason given.

I've actually said quite the opposite. Whilst the genecentric natural selection is superior - it is much more difficult to grasp than simply survival of the fittest (survival selection) coupled with reproductive ability (fecundity) etc. Of course, just looking at the simple bits of a model is not discussing the exact and precise details of it, are they? Yes, Hoot Mon introduce genecentric natural selection and some people were almost outraged by the idea and railed against it. I came in to support this view point as being superior and slowly people have begun to accept its import. If only they will concede that Hoot Mon has been on this since page 1.

Irrelevant, you say? Merely theoretical mathematics? I wish Daniel Hartl were around here to explain why he thinks "The Hardy-Weinberg principle has important implications for population genetics." (Essential Genetics/A Genomics Perspective, pp. 507-10).”HM

You said earlier: I say that the gene's eye view ignores this because it isn't natural seleciton. Your bad luck scenarios are akin to random selection (ie selection happening to an organism regardless of its genetic heritage) and I don't believe that random selection is part of natural selection. I think it is quite possibly more akin to genetic drift.You basically said that 'selection can operate on non-inheritable characteristics'. I agreed, but stated that this selection is not natural selection.

I never said HW wasn't important in its particular context (all the nice equations generated by population geneticists describing nice neat theoretical - read non-existent - populations). Science needs theoretical constructs, and they truly have their place. I don't know where ecology would be today without the abstruse mathematics of Wilson/MacArthur's equations, for instance. Probably still back in the amateur stamp-collecting of natural history. However, they would not be my first choice of method for explaining why there are more endemics on oceanic vice continental islands, for instance - even though they were created specifically for this (among other things).On the other hand, what I was trying to point out is that HW has actually no relation to the real world except in the abstract. If you (that's a generic "you", not Hoot Man necessarily), want to try and explain natural selection to someone who doesn't know much about it, trying to simultaneously explain HW equilibrium and the difference between a mathematical model and reality AS WELL as trying to get them to understand NS would seem to be the most difficult way of going about it that I can imagine. So my advice, don't get wrapped up in the math until you are sure you grasp the fundamental concepts.Of course, all you have to do to prove me wrong is present one single study of a real-world, sexually reproducing population that HW actually describes.

Yes, I know you've said that repeatedly. I'm not sure you've actually gone so far as to demonstrate that contention, although you may believe you have.Since you prefer the reductionist viewpoint, riddle me this: how does one predict the fitness of an organism based solely on the activity of a gene or suite of genes? After all, the properties of an organism - its phenotype - are not simply the sum of the properties of its individual genes, correct? Is the fitness of an organism in its particular environment dependent solely on genetics, or is fitness a phenotypical characteristic? Do allele frequencies in a population change over time because of the activities of genes (IOW, is the gene an agent), or because of the phenotypical effects? Is it possible (outside of a purely theoretical mathematical construct) to calculate the fitness of an allele without merely abstracting from the measurement of fitness of an individual organism? Do genes play a causal role in fitness?ABE: OF you don't want to tackle the above in this thread, how about a simpler question. How does the genecentric view allow one to distinguish between selection and response to selection?Further to what I outlined for Hoot above with my little toy example, I readily agree there is selection of genes, suites of genes, alleles, etc. But what is being selected for is the phenotype - the expression of those genes, etc, in the individual. Edited by Quetzal, : added a bit easier question

Yes, I know, he's looking beyond the simple before having grasped the simple. But I already said I was going to stop pestering you for help with Hoot Mon. I said I was going to discuss only your views and views you say you agree with, because it appears we don't agree on something as basic as natural selection. We can't compose a coherent explanation for someone else if we ourselves disagree about its nature. A simple diagram of Darwin's concepts of natural selection and descent with modification is insufficiently explanatory for you? Ah, well, what can you do...Anyway, my purpose for introducing the diagram wasn't to explain natural selection, but to highlight why your view that natural selection is a consequence of differential reproductive success is backwards. As you follow the diagram downward and forward in time, natural selection is followed by reproduction (descent with modification). Reproduction, the stage where differential reproductive success occurs, is a consequence of which organisms were selected to reproduce on the basis of fitness. No, it is merely using an animal's life for illustration. The diagram is about evolution, which is a struggle for survival (natural selection) for the privilege to contribute progeny to the next generation (reproduction, or descent with modification). Selection precedes descent with modification (where differential reproductive success occurs), not the other way around. I'd like to agree with you, I really would, because I feel exactly the same way, but it would be more believable if you weren't taking issue with so many other views of selection. I'm merely advocating the simple view of natural selection first put forth by Darwin, and I began with the simple approach because of the difficulty Hoot Mon was having with the concept. But before resuming that discussion I think it important for the rest of us to reach some consensus about what natural selection really is. You must not have said what you originally set out to say, because you first say that some types of selection have "nothing to do with natural selection," then you critisize the "individualist view" for missing elements of natural selection. It sounded like you were starting out to say that the individualist view misses the types of selection that aren't natural selection. And I'd love to return to the question posed by the OP, but I'd like to get some consensus first. A unified theory of natural selection, huh! I actually agree with you. You've mistaken the simple way I prefer to introduce the concept of natural selection as indicating that I equate natural selection to survival selection. I don't. I already think of natural selection in terms of what you're calling superselection. The nuances of natural selection can be filled in after the basic concept has been successfully communicated, that's the way I'm approaching this.--Percy