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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
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Author | Topic: Is there more than one definition of natural selection? | |||||||||||||||||||||||||||
Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
Is there only one way of looking at evolution?
I'd say the answer is a resounding "No!". 1. Darwinism 2. Lamarckism 3. Creationism 4. Disneyism... ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
RAZD writes:
Natural selection operates on the phenotype of individuals, whether it is survival, disease, disability or sexual reproduction.
Does NS “operate” on the phenotypes of individuals, like a surgeon who operates on a patient’s liver? Or does it “operate” instead on the reproductive success of populations? NS engages when that success is not uniform across individuals? I think there is a cause-effect relationship to consider here. Is NS a cause or an effect? Neither? Both? Here's how I see it. NS, in and of itself, does not occur at the individual level. NS is about a population’s differential reproductive success. You can’t have evolution occurring in individuals, only in populations. Whatever alters a population’s uniform success in reproduction may have multiple causes”environmental factors, mutation, gene flow”and NS may not always, or not even often, play the lead role in evolution. This issue seems like old dirty laundry to me. Why haven't we cleaned this up? ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
cf wrote:
NS selects among individuals.
crash, I don't think so. I think this notion is a large part of the confusion about what exactly NS is. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
RAZD wrote:
When an individual dies the rest of the population is unaffected. When an individual reproduces the rest of the population is unaffected. Natural selection therefore operates on the individual as expressed in the phenotype based on their genotype.
I simply do not understand that statement.
The effect on the population is the sum of the effects on the individuals,...
So, NS occurs where exactly? In the population or in the individual?
...and there is no effect on the population that is then transmitted back to individuals to affect their existence.
I don't entirely get this. Who ever said that, anyway? All any individual can do to affect evolution by NS is to make gametes and have sex hopefully. Meanwhile, evolution by NS goes on in the population. Indeed, the selection of beneficial alleles in that population is what is really going on, I think. btw: As I'm sure you know, Darwinian evolution by NS was postulated on the Malthusian principle: Populations often produce more individuals than available resources are able to sustain. The whole thing rides on a train called Population. Individuals do not have to go through Door #1 marked "Naturally Selected" or Door #2 marked "Naturally Not Selected" like quiz-show contestants. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
crash:
crash, I like your weebles but I have just addressed this issue in my comments to RAZD in Message 236. I don't understand why. Tell me where I'm wrong in this example...That's natural selection. It operated on individuals, selecting camo weebles over orange weebles. It had an effect on the gene frequency of the population; the camo gene increased in frequency (from 25 to 40) and the orange gene decreased in frequency (from 25 to 10.) Natural selection operates on individuals; as a result, it shapes populations. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
So, NS occurs where exactly? In the population or in the individual?
In the individual. You are far better off, IMHO, to let NS have its way with populations than to say that individuals are the ones being selected. Individuals are only the carriers of beneficial, neutral, and harmful alleles. Individuals do not move forward in the course of evolution, but alleles do. Therefore, NS “selects” for the alleles in a population, not individuals. There has never been an individual anything that has successfully evolved into something else. There was never an individual fish that evolved into an individual amphibian. That kind of morphing goes on in populations when their alleles get sorted out. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
cf wrote:
Individuals are selected - and populations are comprised of individuals.
But where to the individuals go in the course of evolution when that are "naturally selected"? Through Door # 1 to lay down and have sex? Don't unworthy or undesirable individuals sometimes get to have sex, too? Please see my post to RADZ above in Message 240 ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
"Naturally selected" means "lived long enough to reproduce." No! The "naturally un-selected" individuals often get to do that, too. Think about Rwanda. “Naturally selected” means that a population has experienced differential reproductive success. There are no NS agencies going around picking out individuals who qualify to have sex and then makes a bed for them; that's more like "sexual selection." NS, instead, is going around populations of individuals picking out alleles that are disproportionately favored when that population is undergoing differential reproductive success. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
cf writes unwisely:
Except that natural selection can't pick out one allele. You can only knock out one individual's alleles at a time, because natural selection operates on individuals. Why don't you get this, yet?
If individual A is selected to mate with individual B and they successfully produce offspring, neither one of them, as individuals, will evolve by NS into their offspring. Of course you know that. What actually is selected and what actually evolves is that complex of alleles mixed together from individuals A and B, which in combination somehow succeed to make other successfully reproducing individuals. So, you see, individuals can only live their effemeral lives and die without ever experiencing the joy of evolution. They don't get to go to Darwinland. But their alleles might have that pleasure, if they are good enough. Please, once again: No individual can be selected by NS or evolve by NS because every single individual lives but one life.* I think RAZD is mostly right about phenotypes being selected by NS. And phenotypes mean genotypes, of course. NS works on those phenotype/genotype complexes, not on the individual carriers of them. It may be worth noting here that very few phenotypes are carried by individual gametes when they unite in fertilization. For this reason, I see genotypes and their alleles as the true loci of evolution by NS. ”HM *Why don't you get this, yet?
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
If individual A is selected to mate with individual B and they successfully produce offspring, neither one of them, as individuals, will evolve by NS into their offspring.
....what? "Evolve into NS"? I see that we've passed the point where you can construct meaningful statements about biology. We hit it eventually, every time, it seems. That's downright shabby! You ought to be whipped with a cane.
For the third time, stated differently - some of those lives contain the production of more children than the lives of their peers. Some of those lives are long, with much mating. Some of those lives are too short to have mated at all.
Nah, I ain't goin' back there. I've been to the weebles. Done that. Now I'm going to TVeebles to watch pro football. Go Seahawks! That's why natural selection operates on individuals - because individuals have lives of different length, with different amounts of reproduction occurring therein. Do you understand, now? Go back to the weebles. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
[Seahawks...ugly. Booo!]
Hrm, could have sworn. Weird.
That one goes into your permanent record. And it's not the first one, either!
Well, fair enough. My bad. So we're agreed, then? NS selects among individuals? Without resorting to the weebles, I think it is fair to say that NS uses individual organisms as software stores, stocked with beneficial alleles, from which it makes its selection. Remember, individuals are not the ones that evolve. Individuals die early and become dirt. But their alleles, even without much phenotyplcal protection by haploid gamete cells, are the things that actually get selected by NS and survive an evolutionary event...and they survive their host organisms many, many times over. crash, what's the point of NS selecting an individual if it is certain that the individual will die? You're looking in the wrong place to find the survivability meaningful to evolution by NS. Evolution by NS happens when a population fixes new beneficial alleles in some significant way. Your individuals can be selected by each other to have sex, of course, but this is not the same thing as NS, this is only sexual selection. All any individual can do to participate in NS is to make gametes, have sex, and die. Meanwhile, down at the genome ranch, what is really being naturally selected are the beneficial alleles of a population. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
crash, you are confusing sexual selection with NS. Sexual selection happens when there is disproportionate mating amongst individuals of a population. NS happens when there is differential reproductive success across individuals of a population.
Having sex. That's the point. Getting to have sex.
Nah. You're talking about sexual selection”differential mating success. That's not what NS is.
but that shouldn't make us lose sight of the fact that, ultimately, selection shapes populations by restricting the diversity of individuals.
And I can only see your individuals as perfunctory camels, carrying their allelic burdens to a marketing oasis, where their cargoes will be selected like dates for their usefulness and desirability. ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
crash, I don't think you understand what NS really is. NS arises from the differential reproductive success amonsgt individuals across a population. Differential mating success may or may not leading to NS. There is no rule that requires sexual selection to lead to NS. They are two different things. Sexual selection may go on in a population without any NS occurring at all.
btw: I wouldn't be too distracted by the word "natural" in NS. It was put there by Darwin to differentiate his theory from "supernatural selection," if you will, or otherwise "Creation." ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
HM:
Mod: Sexual selection may go on in a population without any NS occurring at all. Then it isn't sexual selection. At least not sexual selection in the sense Darwin proposed, and later biologists perfected. While I certainly do agree that some kinds of sexual selection can lead to evolution by NS, I cannot agree that sexual selection and NS are the same thing. There is no reason I know of that requires sexual selection to automatically invoke NS in a population. I don’t really know if anyone has even postulated this before, so here goes nothin' . Why couldn’t sexual selection be a means for a population to avoid NS? If sex was invented as a means for a genome to avoid its genetic parasites, then why couldn't sexual selection have been invented as a means for a population to avoid the trouble of NS? Hey, if you've got an allele for a big, ugly nose, who's going to want to mate with you? Sexual selection, then, would certainly not seem not to favor NS in the direction of big, ugly noses. Ay? ”HM
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Fosdick  Suspended Member (Idle past 5531 days) Posts: 1793 From: Upper Slobovia Joined: |
Sexual selection does not invoke natural selection. Sexual selection is natural selection.
Let's test my proposition that there can be sexual selection without NS: In a hypothetical population of 100 individuals”50 males and 50 females”the good-looking ones go first and rest mate up with what’s left, but everybody is happy. That’s sexual selection, pure and simple. Now, the good-looking ones and the bad-looking ones have equal fecundity in this hypothetical population; each couple has exactly one girl and one boy. Everybody in the population has reproduced with equal success. So, in this scenario, there was sexual selection without NS. If you can’t eliminate this scenario from the realm of possibilities, then you can’t prove that sexual selection is the same thing as NS. ”HM
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