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

Hey Paul, Paul here. I concur.Answering the question “where does Natural Selection occur?” has only one answer: the entire suite of genes of an individual. The effect of Natural Selection occurring on millions of individuals over many generations brings out specific genes, or rather small suites of genes, which appear to become prevalent in a population. To say that Natural Selection, over the long haul, selected for or against specific small suites of genes is not incorrect. But the operating mechanism works on the individual transient package one organism at a time. As I’ve tried to illustrate a few messages above this, we can, and probably have, due to this mechanism, lost some very nice superior suites of genes never to reappear. Natural Selection can promote or destroy superior suites of genes because it can ONLY act on the concerted effects of the whole. Edited by AZPaul3, : Just because.

Thanks Hoot, for opening this topic. Although my position closely parallels AZPaul's (so repeating what he's already said would be pointless), I would like to emphasize a couple of points. One of the first problems I see is there appears to be some misunderstanding of what is meant by "natural selection". We can argue over whether or not the term is either useful or descriptive (I personally think it is neither), but it is one that has been in regular usage for 150 years since Wallace and Darwin first coined it, so we're pretty much stuck with it. Their attempt to differentiate "natural" vs. "human-directed" evolution is what is leading to many of the difficulties (as others have sort of noted). Unless we are going to postulate that humans are not "natural", then whatever we do to a population is indistinguishable from what the environment does to a population.In essence, then, anything that affects the fitness of an individual organism is "natural" selection. The key word here is selection, not the adjective modifying it. Any filter that affects the survival, reproductive success, or reproductive rate of the individual members of a population is natural selection. Hence, when we talk about "sexual selection", or "kin selection" or whatever selection, we are referring to specific types of natural selection. The terminology can be confusing, I admit. However, when biologists/ecologists, and others of that ilk bandy those terms about, the whole edifice rests on the unstated understanding that in every case it is all natural selection.There are, of course, non-selective forces. As we discussed in a previous thread, genetic drift, etc, don't rely on the actions of natural selection. This is probably why we often hear the formulation "evolution is the change in allele frequency in a population over time". This formulation allows us to include epigenetic factors, drift, etc, in the definition of evolution. Our discussion in THIS thread, IMO, should be limited to natural selection, however. I'm not sure why you feel that if natural selection refers to the factors relative to the reproductive success of an individual organism there should be any confusion here. As PaulK pointed out, in some instances it may make sense to discuss the contribution of particular genes or gene complexes to the survival of its organismal "packaging". After all, it is the gene, not the organism, that is the unit of inheritance. On the other hand when we're talking about selection writ large, to me it doesn't make sense to discuss "gene selection" except in the larger context of selective pressures on the individual organism. After all, there are (to my knowledge), no environmental factors that can reach inside an organism's body to directly affect a single gene or suite of genes without ALSO affecting everything else about the organism.I think some of the problem arises from a misunderstanding of Dawkin's "selfish gene" concept - it's a problem he acknowledged, which is why he wrote The Extended Phenotype. Quoting:

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I want to argue in favor of a particular way of looking at animals and plants, and a particular way of wondering why the do the things that they do...What I am advocating is a point of view, a way of looking at familiar facts and ideas, and a way of asking new questions about them. (Dawkins R, 1999, pg 1)

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In short, Dawkins is saying here that the selfish gene concept is not a fact, but a way of looking at facts. I can think of a number of places where it is an exceptionally useful way of looking at facts - ethology, evolutionary developmental biology, etc, are all sciences well-served by the concept. However, I find it utterly useless for sciences such as ecology, conservation biology, population genetics, etc. In these latter, looking at the action of natural selection as it affects either organisms or whole species makes more sense. Therefore, probably from my own biases and experience, I find the use of the individual organism as the "target" of the selective filter to be the most relevant.

And to be more strictly accurate, at the individual level selection works on phenotypes, not genotypes. Maternal effect genes affect the fitness of offspring whether they carry the gene or not. Developmental abnormalities can be lethal even if they are not genetically based.And it's not just selection. Before a gene spreads widely it is vulnerable to misfortune. An accident can easily remove a single individual. In some species the death of a parent can doom the young. A local disaster could eliminate a family. A beneficial trait typically only loads the dice slightly in favour of the individuals carrying it.

Well, you are certainly not talking about "evolution" my grandfather passed down to me and the concept I can recognize in my parents generation as an essay response to nature vs nurture and the one that I can recognize Gould tried to write beyond. You are talking about something that only the modern digital/academic world could contemplate.If you wish to give up on the idea of the "evolutionary individual" and the 'plurifaction' of genetic possibility taken adavantage of by the next generation of students of biology I fear you have cashed out, through Von Neumann's brain power and memory, the phenotype problem of the 60s (neutral evolution etc)that gave strength to our present disagrement (in this and the thread this thread gave rise from) over the focus of selection beyond the simple US vs UK preferences into one that only your avatar would not form a culture of blinking towards.You are strugggling with the various proposals of hierarchy in biology. Gould for instance did not accept Eldridge's division of geneological and economic hierarchies, Gladsyhev added another one and then there is the simple level of organization issue. If it is true that memes died out because people could not really communicate over them then it seems that your inclination is on *that* side of the discussion.It may indeeed be possible to reduce selection at the level of the individual for a compressed divide to an encoded smaller entity but why did you not recognize this traditional history which you surely must extripate before your notion would be commonplace. Is it simply because you wanted to speak about the the thought that HW may not occurr in a lot of populations??If that were the case then why did you not discuss Fisher's ideas vs Wright's where instead one DOES have the issue of speciation with the maths dependent on population structure vs. a large random breeding population??It seems to me the only reason that UK biologists prefer selection over what one often can hear from US biologists is that like the idea that Whitehead said, UK is for the sea, France the land and Germany the clouds(+/-), the British by sticking with the individual would never drown, the French DID criticze Wrignt at area polymorphisms but made it topological/psychiatric while the Germans with Henning simply opened a bit the level difference for a programmer without providing the goal.Only a meme can communicate that biologically and yet these died out in the technical literature (look at the rise and fall of papers published on memes) so if the culture can not support the reduction the only hope is Wolfram, but so far his ideas would not even stand inside of this, as far as I think about reductionistically and BEYOND what I was taught traditionally.Why? because the analysis has not been carried to the extreme and the simple reductionist prejudice is in it's place.If the individual is the vehicle then ANY hierarchy must be addressed and you did not do this with higher, lower, individual, kin, gene but your's remained within the phenotype debate itself and thus you subjected your hierarchy to the evolutionary individual at best but at worst you would need to intricate the kin to the gene to a higher level by showing in detail the difference of sexual selection in plants vs animals, no matter the adaptation, IN TERMS OF WHAT OLD selection language needs replacing with what reductionism but I can neither cognize that physical case nor imagine any physical phenomenon that that would envelope. If you can feel free to say so as I would love to logos my biological organon.

Good God, man, do you practice obfuscation for the fun of it? Is it congenital? Nested sub-references 3 layers deep, juxtaposed syntax with reference outside the structure or no reference at all, run-on sentences without even the thinnest hint of relation subject to verb . If you've got something to say, Brad, then say it without all the sub-references and do try using some kind of recognizable structure. You are not coming through. Your efforts, and mine in trying to translate, are wasted.You have some kind of problem saying, “I would be happy to discuss my philosophy with you?” Logos my organon, indeed.I do hope this is a written affectation. God help you if you speak this way in real life.

You got Brad McFalled!

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Since whatever is being selected must be somethng that can be inherited and must be something that we can find in many individuals, it makes more sense to look at genes. The view of a single gene working in isolation is certainly oversimplified but - for sexually producing organisms - it comes closer to what is actually going on.

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Does the distinction "selected for" and "selected of" help the situation? That is, there is selection of genotypes for for phenotypes. And the genes that can work well with the most assortments of genes get selected (the genes that are incorperated in the most number of successful genotypes), but their success is rooted in the sum of the effects of the entire genotype on the phenotype, that is the individual.I'm not sure if I said anything opposed to your position or not; i'm thoroughly confused wrt to "the unit of selection".

I think that the issue is that the question of where natural selection happens is ambiguous.If we want the actual events then those happen at the individual level where phenotypic advantages tilt the odds towards reproductive success.But trying to see the evolutionary effects of speciation by doing that is lik looking for a forest by examining each individual tree. A higher level, aggregated view is more appropriate for that case. And that view will be closer to a gene-oriented view.So either approach leads to a valid answer to the question. I'd tend to use the second approach because it is more directly relevant to evolution. But a purist might well object that it is an idealised, simplified view that ignores the details.

You are, of course, correct. Depending upon what one wishes to accomplish one gets closer to or further from the tree.So to sum up, the mechanism of Natural Selection, in detail, operates at the level of the individual, and in effect, operates at the level of the gene.Hey, Hoot, it's your thread. Whatch ya think?

You wrote,

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and in effect, operates at the level of the gene.

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but HM copied into the OP

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Looking closer, as did G. C. Williams, Wm. Hamilton, R. Dawkins, et al., the actual site of natural selection can often be seen at the level of genes and their alleles (i.e., genetic evidence of strategic altruism for kin survival).

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HM doesnt think

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So to sum up, the mechanism of Natural Selection, in detail, operates at the level of the individual, and in effect, operates at the level of the gene.

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He is looking from the wrong the place to start from but he thinks he can use Williams, Hamilton and Dawkins et. al.in support of from whence it has been ever since Darwin...I disagree. (By the way, I was not expecting you to respond to me as I was kinda agreeing with what you wrote earlier, HM did not fully seperate the hierarchies and thus he got away with his assertion (but look at what others said in this thread, including you. HM will have to give up on a long tradition that attempts to discuss the multiple interrelations of genes with soma. I find biology much less interesting in that context.)Would you like me to discuss Gould's ideas that Dawkins' and Williams' approaches can be seperated? and thus try to relate that back to the thread from there, which is clearly "evolutionary".Edited by Brad McFall, : he-HM

I would appreciate that very much, Brad. But only if you can structure it in such a way that a poor country bumpkin can understand.

No, it's not. Natural selection operates on the changes of allele frequencies resulting from preferential mating. Preferential mating, in and of itself, is not what is “being selected for.” It is the result of it that opens the door to NS.”HM

Perhaps not, it may just be a runaway mutation.But on the other hand, it could be selected for. Given that there may be a genetic component to our preference in mate, would not those who wanted the 'fitter' mates be selected for? Would not that mating preference be conserved?

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"And, lo, a great beast did stand before me, having seven heads, and on each head were there seven mouths, and in each mouth were there seventy times seven teeth. For truly there were seven times seven times seven times seventy teeth, meaning there were. . . okay, carry the three, adding twenty. . . plus that extra tooth on the third mouth of the sixth head. . . Well, there were indeed a great many teeth" - The Revelation of St. Bryce the Long-WindedHelp inform the masses - contribute to the EvoWiki today!

The “handicap principle” is interesting enough. But it might be looking at natural selection from the wrong angle. The handicap theory, as I understand it, was proposed to explain why certain individuals adopt dangerous behaviors for mate attraction that actually reduce their chances of survival. In human terms, one can envision the risk-taking teenager, Johnny, foolishly behind the wheel or heroically out on the football field, using the handicap principle to attract a pretty girl.Thus, if Johnny dies on the railroad tracks or gets paralyzed from the waist down in a football game, how is he going to have children to carry his genes forward in space and time? The handicap principle is tragically self-destructive.But wait. What if Johnny, a mere pawn in the game, was a strategic move on the genes' part, operating under the principle of genetic altruism? Hamilton, Dawkins, et al. have argued that genes can be quite strategic in their adaptations for survival, even to the extent of demonstrating altruistic determinsim. So, individual survival may NOT be the real focus of natural selection; instead it would be focusing on the genes and their alleles, or on changes in their relative frequencies thereof.”HM

You're not making any sense. "Operates on the changes"?Preferential mating alters allele frequencies in the direction of the preference; thus, it's a form of selection.If you're going to rebut this, you're going to have to bring something to the table that isn't your usual garbled nonsense. No, of course it is. If the preference of females is for bright feathers, then males that have drab plumage are selected against, and allele frequencies are driven towards bright plumage. If the preference of females is for the male who wins strength contests, then males who can't win such contests are selected against, and allele frequencies are driven towards weapons, like the large curling horns of mountain rams.Preferential mating is selection - sexual selection. No, it doesn't. Preferential mating is sexual selection.Edited by crashfrog, : No reason given.