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

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.

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 worried that our discussion is pushing us both to extremes, when really, it's probably true that the gene view and the organism view are both valid approaches that serve to illuminate different types of questions. I know that I, personally, am susceptible to creeping dogmatism, and I don't want to head in that direction.Mostly what concerns me is the possibility that Hoot Man will have so much of his nonsense validated by well-meaning people who use his clumsy, inaccurate references to scientific controversies he really doesn't understand as a springboard for interesting discussions, such as the one we've been having. Like Buz, he's got somewhat of a tendency to act as a flashpoint in that regard; also, like Buz, he incomprehensibly tries to take credit for it.

I'll live, thanks for your concern. I'm not yet convinced that there's not hope for you - that is, if you can ever get rid of that big chip on your shoulder. How do you carry that thing around without getting tired?

I do, yes. It was all that material that you excised to misrepresent what I was posting in that thread. Is there some reason you weren't able to reply to it?Edited by crashfrog, : No reason given.

How did you get that from what you quoted?

quote:

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Even in a population undergoing no appreciable selection, genetic drift is causing changes to the allele distribution of the population.

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Those were my words, but I don't see where I used the terms "natural selection" or "groups" in any of that.Go back to the classic example - bacteria and antibiotic resistance. Individuals who are resistant survive, individuals who aren't, do not. The subsequent generations are all the descendants of those individuals who survived, which means they're also resistant, and so now you have a population that has evolved resistance by selection of individuals.The things you write are nonsense, because apparently you don't understand what words mean. That's the only explanation I can offer for why you understood what you quoted to be referring to "natural selection of groups," language that does not appear in the quoted section. A house has walls and a roof, but does that mean that a roof is a house? Or that a wall is a house? You're confusing the process with the result. Natural selection is one of the processes that result in evolution of populations.

That can't be right, can it? Even the maximally simple population, the Hardy-Weinberg population, moves towards equilibrium, doesn't it? And wouldn't mutation also cause changes in allele frequencies?

By "Hardy-Weinberg population", I meant to refer to a population operating under the strictures assumed in the Hardy-Weinberg equation, to wit:

quote:

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The original assumptions for Hardy-Weinberg equilibrium (HWE) were that the organism under consideration:

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* Is diploid, and the trait under consideration is not on a chromosome that has different copy numbers for different sexes, such as the X chromosome in humans (i.e., the trait is autosomal)
* Is sexually reproducing, either monoecious or dioecious
* Has discrete generations

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In addition, the population under consideration is idealised, that is:

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* Random mating within a single population
* Infinite population size (or sufficiently large so as to minimize the effect of genetic drift)

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and experiences:

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* No selection
* No mutation
* No migration (gene flow)

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and by "moves towards equilibrium", I mean that, even under the Hardy-Weinberg assumptions, the allele frequencies, starting from an arbitrary distribution, reach the distribution specified by the Hardy-Weinberg equation (aka HW equilibrium) within a few generations. Obviously a mutation that creates a new, mutated allele has just changed allele frequencies. If you imagine a population of 100 where:25 are homozygous AA;
50 are heterozygous (Aa);
25 are homozygous aaand, one homozygous individual experiences a germline mutation to a that creates a new allele a', you now have new frequencies:25 AA;
50 Aa;
24 aa; and
1 a'a.See? Mutation alone can change allele frequencies. You went from a frequency of 100 A and 100 a to 100 A, 99 a, and 1 a'. When you say words like "homologically", I have no idea what you're talking about. Homology is defined in a biological context as:

quote:

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any similarity between structures that is due to their shared ancestry. There are examples in different branches of biology. Anatomical structures that perform the same function in different biological species and evolved from the same structure in some ancestor species are homologous. In genetics, homology is measured by comparing protein or DNA sequences, and homologous genes share a high sequence identity or similarity, supporting the hypothesis that they share a common ancestor.

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It's not clear from your usage of the term how you intended it to apply to anything that we're talking about. Can you clarify? I can't answer a question that I don't understand. I assume you meant "or", there, because genetic drift is non-selective. But, no, my point is that mutation alone is another influence on allele frequencies, in addition to selective forces and genetic drift.Sorry, references: Hardy—Weinberg principle - Wikipedia and
Homology (biology) - WikipediaEdited by crashfrog, : No reason given.

I don't understand how you're back to the same mistake as before. Clearly a process called "sexual selection" is not best described as non-selective?If sexual selection is non-selective, then how does it result in traits like the bright feather displays of male peacocks or the curling, protective horns of rams?

Then clearly sexual selection is a kind of natural selection, because sexual selection causes differential reproductive success.It takes two to tango, as you may be aware. If females prefer to mate with, or are even exclusive to, males that have prominent displays or males who win intrasexual combats, then differential reproductive success is created - males who have those displays or can win those combats reproduce more; males with no such displays or who are the losers of such combats experience less reproductive success, or perhaps no success at all.Clearly female mate choice represents a selective force. It's not clear to me how this can be denied after so many examples. I'm not sure what any of that has to do with sexual selection. Sexual selection is not genetic drift; it's natural selection. There's nothing non-Darwinian about sexual selection; indeed, it was Darwin who came up with the concept.

You're talking about the guy who says that sexual selection is non-selective. You know that, right?Am I the only one who sees those posts, or what?

I don't see that there's a need to do that. Sexual selection is clearly consistent with natural selection in every accepted way to formulate it. Obviously it does; if you're a male with no bright plumage, for instance, and no female chooses you for mating, then clearly your contribution of offspring to the next generation is zero, which would be different than the males with bright plumage who were selected for and were allowed to mate. It's not clear to me how many different examples I have to use to inform you that you are wrong about that. Completely wrong. Sexual selection is a form of natural selection, a fact understood by Darwin and every subsequent biologist. There is no one who considers it this way besides you. Sexual selection is recognized by every biologist as a form of natural selection, being that it is a selective influence on the gene pool and results in differential reproductive success, per definitions you yourself have supplied. What's the mental block that's preventing you from seeing this?

Regardless of what you choose to call it, it's clearly selection, as I've proven in countless different ways. Are you capable of a reply on this subject beyond "it's not selection because I say it isn't?"It's clear that we've gone way beyond your understanding, here. Why don't we back up and you can explain exactly what you're having trouble with?

I'm sorry, I guess I don't understand. In the message I replied to, there's no quote that appears after your remarks on HM's supposed cogency. Are you referring to another post? You'll have to point it out, if so.