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

Fallacy of the looming caveat. The vast, vast majority of organisms on Earth, by number or by weight, are asexually-reproducing organisms.So I'm not sure it makes any sense at all to try to define the focus of natural selection based on the behavior of sexual organisms; such organisms are little more than a corner case in the grand scheme of things.

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So I'm not sure it makes any sense at all to try to define the focus of natural selection based on the behavior of sexual organisms; such organisms are little more than a corner case in the grand scheme of things.

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I didn't think I was saying that. I meant to get across that "reproduction" makes more sense in asexual individuals than sexual individuals.Of course, the meanings of words change so I'm not trying to say one connatation is wrong. But with regard to "differential reproductive success" I think the form of reproduction that is being implied is the asexual kind, i.e., produced again with a high degree of fidelity.This type of "reproduction" applies to genes, haplotypes, etc. and the entire genotypes when talking about asexually reproducing organisms. Edited by JustinC, : typos

The problem I have is that I cannot imagine describing natural selection occurring on soldier ants if we consider them simply as individuals to select from. Indeed, any altruism becomes difficult to explain, unless we start talking about selection pressures acting on genes rather than individuals.

Nothing to argue with there, and I might reconsider my approach if someone said, "Define natural selection, but you have to use soldier ants as your example and you have to tie it in to altruism," but it's not an approach I would associate with simplicity and clarity. We're having difficulty just getting across the point that sexual selection is a type of natural selection, so framing the definition in terms of genes would only seem to add more opportunities for potential confusion.I think the Dawkins' perspective is widely recognized as not the best way for introducing the concept, and this is backed up if you go and look up a dozen definitions of natural selection around the web. As Quetzal said, it might be a better perspective for population geneticists, but discussing evolution from a population perspective is not one with which I've had much success with creationists, perhaps because it isn't very intuitive for many people.But defining natural selection as the environment placing pressure on an individual's survival through its characteristics, its phenotype, is something grade school kids understand, and before going too far with any discussion about natural selection I'd want to make sure it is understood at that level, the level that E. O. Wilson used in the excerpt I provided in Message 88 using birds' eye color.I hope I've been clear that I'm not saying you're wrong or that Dawkins' is wrong. I think we just disagree about the best way to introduce the concept of natural selection.--Percy

I don't understand what you mean by 'gene frequency.' Perhaps you really meant to say 'allele frequency'.”HM

Fine. You're entitled to your opinion. I have the very same opinion of you and those who prefer to see individuals evolving via NS. But YOU have never explained how an individual "evolves" by way of NS. Instead you just make hollow accusations about other peoples' perspectives and understandings. Please tell me how an individual organism can possibly undergo NS. Wouldn't it have to have a redistribution of its allele frequencies within its own lifetime? Just how does THAT occur?”HM

In fact, nobody but you has asserted that individuals evolve. Individuals are selected. Populations evolve. By being killed; or by failing to reproduce with the same success as more fit individuals; or by reproducing more than its conspecifics. What? No. You're confusing the fact that selection acts on individuals with the effect selection has, in aggregate, on populations. Individuals mutate and are selected. Populations evolve.

We don't disagree. I think talking about successful phenotypes making more successful offspring and the like is the best way of introducing the topic, and of discussing the topic in general terms. I'm only bringing this alternative view of natural selection here because of the thread title and the discussions that have taken place here.Seemed like Hoot Mon was getting short shrift from some for suggesting genecentric natural selection to me. I thought I'd add my thoughts, since this is a legitimate biological debate If you can have a shot at defining natural selection in terms of individual soldier ants, that would be interesting, but I'm not laying down a gauntlet or anything.Edited by Modulous, : No reason given.

Have it step in front of a speeding semi. The aggregate suite of genes exhibiting "stupid" would be lessened from the population.Hoot, are you looking at Natural Selection as a "process" rather than an event? Are you confusing Natural Selection with its higher level result Evolution?Edited by AZPaul3, : No reason given.

Clearly they don't experience natural selection?Since the argument is over defining where natural selection happens, and you concede that the genes do undergo some sort of selection - how can we possibly say it is clear that this selection is not 'natural selection'? As you may have noticed, I was simply stating a fact - an entity that does not get selected is not a gene according those biologists that have a gene centred view. I have not stated you have to agree with them because of their qualifications, but I highlighted that they are not regarded universally as kooks and crazies - there are some impressive names on the list of genecentric selection. I agree that there is no total consensus on the mattter. They were mentioned because it is their view of natural selection that was being discussed by Hoot Mon. And then you answer the question anyway... I simply fail to see how this is evolutionarily interesting. A population of sterile organisms doesn't evolve, other than in the sense their gene frequencies change as they die. However, there is no cumulative selection going on, and natural selection should really be about cumulative selection. The reason I don't see this as the best/most accurate way of looking at natural selection is that the individual that is made is not the same as the original. Individuals don't replicate - its the genes that replicate. There is only one copy of an individual in a population, but there are many copies of a gene. When that individual is dead that's it. There are no copies of it that go forwards to the next generation. There are sometimes offspring, but these are their own individuals. In the offspring however, remains copies of the first individual's genes. It is the genes that get copied, that get passed on. It is genes that sometimes get passed on and sometimes don't. Individuals never get passed on.Evolution happens to populations, and not individuals. Natural selection acts on the genepool, altering the frequencies of certain alleles.Dawkins' illustration of this involves rowing. Essentially you have a whole group of rowers. They each specialise in one position. Each position is a gene, each rower is an alelle, and the team is the genome. In this case the phenotype is completely bound by the genotype.You could set up a natural selection time trial, survival of the quickest and all that. Each team gets three races before they 'die'. I realize what you are saying is that the ones we select to be mutated and reproduced are the teams, so it is the individual that is the subject of selection.However, I say that the selection process is more subtle than that. We are selecting certain rowers to be in more future team line ups. We're increasing the frequency they get to be in a given boat. The rowers we are selecting are the rowers that work well with other rowers in the 'row pool' to make teams which are succesful in winning races.Obviously with only four genes, there will probably be multiple copies of certain 'teams' (even with plenty of alelles, I imagine). However, even if the 'rownomes' are identical, each individual team is still a seperate individual team, with their own 'race-span' [life-span]. Edited by Modulous, : No reason given.

No, there are several here who are insisting that individuals experience NS, including youself.crashfrog, how do you differentiate "evolve" from "select"? You can have evolution without selection, but can you have selection without evolution? Well, maybe, if microevolution is correctly interpreted, which is not so easy to do because of considerable disparity in its definitions. Personally, I don't thing individuals either evolve biologically or are selected Darwinistically. My best guess is that allele frequencies are selected for and evolve, dragging along their perfunctory organisms to give them a place to express themselves.In broad terms, there are three conceptual versions of selection: 1) group selection, 2) individual selection, and 3) gene selection. I've read good arguments that 'individual selection' is really a branch of 'group selection', because they are, after all, the breeding units of a population. And I've read good arguments that 'individual selection' is really a branch of 'gene selection', because, after all, there is that appearance of the "suite smell of success' appearance."So, given all that, will you please critique this statement: Individuals themselves don't evolve into anything, they don't experience NS of any other agent of evolution, they merely live out their genetically predisposed lives as incremental and ephemeral tools of homology.”HM

If natural selection is either where organisms experience differential reproduction based on adaptations to environment; or it's where genes that connote phenotypes that adapt an individual to environment are more likely to be replicated in future generations, then the tendency of shorter sequences to be replicated with higher fidelity than longer sequences doesn't count as natural selection, either way.At least not that I can see. It seems to me that it's a kind of "gene selection" that operates not because of the relationship of phenotype to environment, but as a consequence of the genetic mechanisms responsible for DNA replication and sexual reproduction. It's not environment selecting phenotypes in the classical sense of natural selection.But that's just my usage. What the hell do I know? Obviously a dead population doesn't evolve. I think it's important to recognize the difference between natural selection as it operates on individuals, and the result of natural selection, in aggregate, on populations. Gene-focused NS, to my mind, makes this distinction a lot harder to see.Or it's possible that it removes the need for the distinction, altogether. In most cases, it's very much the same. I doubt you could distinguish between one bacterium and its daughter, for instance. Certainly not without a very destructive process of genetic analysis. Sure, but the gene pool is just an abstract concept. In reality, genes aren't sitting there in a big pool; they're sequestered in organisms. Individuals. How are we doing that, exactly? When a boat wins, we have no idea if it won because Speedy McRow, who claims to be the fastest skuller in the land, was pulling one of the oars. In fact we see teams with Speedy lose a lot, and maybe that's because Speedy isn't as fast as he thinks he is, or maybe it's because Draggy Fitzfattrick was in the boat too.We don't know, because all we see at the finish line are the boats coasting in, oars stowed, each individual rower's contribution completely unknown to us. All we can pick are the winning boats. Eventually, as we shuffle the teams, maybe we see that Speedy, plus some other guys from winning boats, makes a really fast boat. Or maybe Draggy's so fat that he sinks his boat and pulls Speedy down with him.

Er, but that's not what I said, was it? Not "experience NS", but "evolve." Again, the only person who has asserted that individuals evolve has been you, arguing against a strawman. I challenge you to quote any other person saying otherwise. I've told you several times, as have others. Individuals are selected; populations evolve.How is that difficult to understand? Let me break it down for you. Random mutation operating on genes, combined with natural selection operating on individuals, leads to evolution of populations. Ok, I guess; but your historically spectacular science gaffes lead me to have little confidence in what you personally think. Individuals don't evolve. They are selected, they do mutate and potentially pass those mutations on, they do experience all the agencies of evolution in their lifetime, usually; evolution is the sum of those agencies, operating on individuals, in aggregate influencing populations.And I haven't got the slightest idea what the hell you're talking about when you say "tools of homology." I think it's very likely you have no idea what the word "homology" actually means.

I'm not trying to accuse anyone of anything, I'm just trying to help you understand the Darwinian definition of natural selection.No one is saying that individuals evolve, so you can just relax your concerns along these lines. But this isn't the first time in this thread that you've concluded that someone was claiming individuals evolve, so if you could point to what it was I said that led you to think this it might enable me to help clarify things. You're confusing natural selection with genetic change. Perhaps it would help to talk a little about where evolutionary change actually takes place. Unlike natural selection, identifying the precise origin of evolutionary change is probably easier to talk about at the level of genes. For asexual unicellular organisms, evolution occurs during cell division. The copying of the original DNA is not a perfect process, and some number of errors almost always result. Neither of the resulting organisms can be considered the parent, and it is possible that both can differ genetically from the original organism.For most sexual multicellular organisms, evolution occurs during the combination of sperm and egg with each providing half the DNA. Not only does allele mixing take place, but once again copying errors play a role, and so it is very common that neither sperm nor egg is a perfect copy of the half-strand of the parents DNA.This precise point where evolutionary change occurs is not where selection occurs (we're not talking about selection of sperm, of course, which only applies in the sexual case, anyway). By the time cell division or combination of sperm and egg is taking place, selection has already occurred. The asexual cell was selected because it is still alive and in a position to take in enough nutients in a sufficiently favorable environment to divide. The sexual multicellular organisms were already selected before the evolutionary event took place, because they were still alive and in good enough health and location to engage in sexual relations with each other. Those that died in a drought or a storm or that didn't have enough strength to make it to the mating island (in time or perhaps at all) and any number of other possible events, these organisms were selected against and so did not have the opportunity to engage in sexual relations in order to produce offspring.The criticism isn't that you don't accept this perspective. As I said to Modulous, though I feel the Dawkins' view has little to recommend it in terms of explication, I do think that it generally boils down to the same thing as the Darwinian perspective. The actual criticism is that you don't understand the Darwinian perspective yet. Your continuance of replies like "No, you're wrong because individuals don't evolve" make the fact, though not the precise nature, of your misunderstanding very clear.If it's just a case of us just not writing clearly enough, then see the Wikipedia definition (Natural selection - Wikipedia) or the glossary here at EvC Forum (http:///WebPages/Glossary.html#N). This is all we're trying to say.--Percy

Well, we probably agree generally that NS is some kind of agency of evolution. Whether or not is is an event is arguable from either side. But, speaking of selection, it would seem to need an event of some kind to make a difference. If individuals are selected for, then is the event occurring in them? Or is it occurring in the homogolical success of their gametes? The second option seems more likely to me”more genetically arguable than the first.”HM