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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
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Author | Topic: What exactly is natural selection and precisely where does it occur? | |||||||||||||||||||||||||||
Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
This new thread topic arose from Message 65:
Quetzal wrote:
”HM replied:I DO understand that selection must, by definition, operate at the level of the individual organism. After all, it's the organism that reproduces (or not). Evolution, on the other hand, operates at the level of a population. I would have thought that would be obvious (and no, this is REALLY not the thread to get into the pros and cons of group selection theory). Yes, perhaps a new thread is more appropriate, because “group selection” and “individual selection” need to be differentiated from “gene selection” and “kin selection.” It must be confusing to MartinV and his ilk that Darwinian biologists can’t agree on exactly what natural selection is and where it occurs. And, unless you invoke the selfish-gene theory, the same quandaries can be raised about evolution itself. By definition, natural selection is the possible consequence of uneven reproductive success of individuals in a population. But this does not mean that natural selection necessarily operates on the individual or its population, even though the results may occasionally point in that direction. 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). “Group selection” and “species selection” (i.e., 'for the good of the group or the species') are no longer regarded as credible by most biologists, although some still claim them to be true. Furthermore, natural selection is not the only cause of evolution. Non-selective agencies like genetic drift, gene flow, and preferential mating may also cause evolution to occur. But who knows for sure exactly where natural selection occurs? And the same question can be raised about evolution. Any thoughts? ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
Non-selective agencies like genetic drift, gene flow, and preferential mating may also cause evolution to occur.
Preferential mating is, by definition, selective. The mate's preference constitutes a selection. That's why they call it "sexual selection", after all. Where does evolution happen? Planet Earth. Next question. No, seriously, though. Where doesn't evolution happen? It happens any time that living things are reproducing through descent via modification. I guess maybe you think you're asking an insightful question, but it sounds like a stupid one to me. Even in a population undergoing no appreciable selection, genetic drift is causing changes to the allele distribution of the population. Then are you are saying that evolution happens homologically. I would agree that evolution couldn't happen without inheritance, but I don't think differential reproductive success (natural selection) is the only tool nature uses to stage an evolution event. Nevertheless, the question here concerns the exact meaning of natural selection and the precise location of its activity. In the case of differential reproductive success, which is a good definition of NS, at which of these leves would you say it operates?: a. speciesb. population c. organism d. kin e. gene We can go from there. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
MartinV wrote:
Maybe if a random mutation constituted the critical difference for NS. But don't forget that there are other agencies of microevolution besides mutations that NS can eventually work on. Alleles can be imported into or exported from a population, and their frequencies can vary due to drift. These factors might also make a genome vulnerable to selective pressures.
Another question is if Natural selection is capable of creating new species. In this case would darwinists put more stress on random mutation that makes possibilities from which natural selection can choose. Of course there are many scientists who deny Natural selection as evolutionary force - they consider it as only maintaing force that removes extremities. Eimer, Heikertinger, Suchantke and all great men mentioned in Davison's Manifesto.
In science there is a thing call the "peer review." You must understand that these "scientists" you mention above would have a very bad day if they tried to float their beliefs at one of those wire-brush scrubbings called a "peer review." It's sciences quality-control mechanism”usually harsh, sometimes bloody. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
Preferential mating is well know as a non-selective agency of evolution.
Huh? Peahens dig males with long tail feathers. Peacocks with long tail feathers therefore get to breed. Peacocks with short tail feathers don't get dates, and so don't reproduce. How in the world is this not selection? ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
AZPaul3 wrote:
Would you say then that NS operates at the gene/allele level of organization, or at the individual level? With those just getting into the swing of things I always liked to define “mutation” as the all-inclusive process of changing the genome and leave the details to come as necessary. With Natural Selection, I define this as what effect those “mutations” have on the individual and leave groups, populations, etc. for a later time. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
HM wrote:
crashfrog responded: Well, it is a kind of selection, of course, but it is not natural selection. Instead it is regarded as a non-selective agency of evolution. A kind of selection is regarded as non-selective? This isn't an issue of semantics, Chiroptera. This is ol' Jocko not knowing sense from nonsense, as usual. Consider this: The Hardy-Weinberg equilibrium requires random mating in the population, otherwise its allele distribution could change if preferential or nonrandom mating occurs. I’m not talking about reproductive success here; this is not about natural selection. Sexual selection is about disturbing the H-W equilibrium, which is considered a non-selective agency of evolution. Natural selection doesn’t apply to sexual selection because natural selection is not about mating”it is about differential reproduction success. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
AZPaul3 wrote:
Then you would agree that natural selection "pressurizes" all the way down to the genetic level? This is different from selecting at the level of the individual, who is only an extant collection of phenotypes, assembled to serve the needs of reproduction, which of course perpetuates those selfish genes. The individual is, of course, the one unit that is affected by Natural Selection pressures. Even when major environmental changes occur affecting an entire species some individuals may be better constituted to survive and procreate. The individual is a “suite” of genes acting in concert. The right mix works, the wrong mix dies . as an individual. The effect is that certain mixes of genes survive, propagate and add to the mix in a population. Dawkins’ “selfish gene” phenomenon is the result. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
Sexual selection doesn't have anything to do with H-W equilibrium...Sexual selection is when alleles increase or decrease ...
What you say, mon? I think you're contradicting yourself. ”Hoot Mon
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
crashfrog wrote:
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. Preferential mate choice causes differential reproductive success; therefore, clearly, mate preference constitutes a selective force. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
Doddy wrote:
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. Mating preferences evolved via natural selection. I'd read about the Handicap Theory, if I were you. 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
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
JustinC wrote:
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. and in Message 32 Quetzal wrote:
In essence, then, anything that affects the fitness of an individual organism is "natural" selection.
and in Message 18 AZPaul3 wrote:
The individual is, of course, the one unit that is affected by Natural Selection pressures.
Does natural selection select for traits, or does it merely select for individuals possessing those traits? In the case of the handicap principle (Message 44), you could say that natural selection may not actually select for mate-desirable individuals, but instead against them. I don’t see how natural selection could act on individuals. Wouldn’t that mean that the individual, somewhere in its ephemeral lifetime, might actually experience natural selection? No, I don’t think so. Individuals come and go. They are as expendable as Kleenex””pull one out and up pops another.’ They only serve to make the gametes and put them where they need to go. No individual ever experiences natural selection. I haver never heard of any human individual say: “Hey, hold on a second, I think I’m experiencing a natural selection!” ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
Quetzal wrote:
Qeutzal, let ask you this: Did NS occur in a individual frog so that, during its lifetime, it evolved into a reptile? Or did 'Eve', during her lifetime, evolve by way of NS from an ape into a human? 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. I think you are others here are placing too much emphasis on what an individual can do in the course of biological evolution. Since no individual survives long enough to actually experience NS, then the operational site of NS must be somewhere or something else. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
Percy wrote:
Percy, I'm in real bad shape if neither the creationists nor the evolutionists agree wth me. Please tell me what I'm missing here. I see five different ways that biological evolution can take place: In other words, your understanding of natural selection differs from both creationists and evolutionists. You might want to rethink things. 1. random genetic drift”population size drops below crfitical level, altering allele frequencies (NON-SELECTIVE). 2. 'gene flow'”alleles sufficiently imported or exported from of population to alter their frequencies (NON-SELECTIVE). 3. random mutation”nucleotide rearrangement, sufficiently to cause a gene to express a different amino acid in a protein sequence (NON-SELECTIVE). 4. Differential mating”non-random mating, sufficiently to alter allele frequencies (NON-SELCTIVE). 5. Differential reproductive success”otherwsie known as natural selction (SELECTIVE, of course). If any one or more of these conditions are met then biological evolution may occur. NS does not always play a part, but it may eventually have a role in selecting for changes in the allele frequencies resulting from the consequences of the other evolutionary 'forces'. Don't you agree? ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
crashfrog wrote:
I try to keep the E. coli off my lawn. Don't you have indoor plumbing? You introduce an antibiotic into a lawn of E. coli. Resistant individuals live but nonresistant individuals die. ”HM
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Fosdick  Suspended Member (Idle past 5528 days) Posts: 1793 From: Upper Slobovia Joined: |
Percy wrote:
Modulous replied: I was only trying to explain that natural selection operates on individuals and that there's really no disagreement about this among creationists and evolutionists. Actually, where selection can or cannot occur is one of those real controversies that biology has had. Here is Richard Dawkins:
quote: ”HM
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