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In response to a request from Ted I have now got hold of a copy of Fisher’s ‘The Genetical Theory of Natural Selection (1930)’. The title suggests Fisher considers inheritance to be a component of Natural Selection; that he uses the same definition as Darwin. Here is a (slighlty abridged) extract:
So Fisher uses Natural Selection in the Darwinian sense. I have updated my diagram.
— Axel147 08:51, 4 July 2006 (UTC)
In fact, neither Darwin, nor Fisher use natural selection in a single consistent sense; Fisher for instance does not include sexual selection as natural selection; now we would. Gleng 17:27, 4 July 2006 (UTC)
Wallace 1871, "On Natural Selection" uses Natural selection as Survival of the Fittest (p302, "meaning simply that, on the whole, those who die are least fitted to maintain their existence" quotng Darwin "Origin" chap III.)
This is clearly circular as a definition, but fine as a description. The circularity can be removed by defining natural selection as the natural processes of selection, as against the artificial processes used by farmers, in which case "Natural selection comprises the natural processes by which some individual organisms survive and reproduce while others do not."
The theory of natural selection states that, if there is heritable variation in a population, then when a component of selection is selection for a heritable trait, that trait will become enriched in the population, and adaptive evolution will take place. The confusion is between whether you use Natural Selection as a name for the theory, which clearly is a common shorthand usage, or strictly for the processes of selection. If you use it for the processes of selection, and seek to explain some effect by this, then it is essential to avoid defining natural selection by that effect, for then your argument will be vacuous. However, this article is not an academic article, and it's most important to be clear; I'd rather avoid well known traps Gleng 16:12, 28 June 2006 (UTC)
OK,:How is this mechanically different from defining natural selection as "Natural selection comprises the natural processes by which some phenotypic characteristics are preserved while others are not." This is fine as a description or characterisation of natural selection. To put the creationist argument bluntly, it is in part that the theory of natural selection is dogma not science, comprising unscientific (unfalsifiable) assertions. There is some validity in this because if we define anything by its effect, then we lose the power for it to explain that effect - and if we define natural selection in the above way, the statement that some traits are enriched in a population as a result of natural selection becomes tautological, unfalsifiable, and vacuous; it is simply an assertion of something true by definition, but which might be trivially true if the definition does not in fact apply to anything. If natural selection is defined in an open and simple way however, the same statement becomes a bold prediction and is falsifiable, and is true only when some sources of variation are heritable and when there is some component of selection for heritable traits. Gleng 16:11, 5 July 2006 (UTC)
Yes, it's true that I'd prefer a definition that makes this key argument easier to make, and yes I agree that the power of the theory isn't affected one way or another; as for using a different definition from Darwin - well Darwin said things in different ways at different times too, but I think the main sense in which he used natural selection is as opposed to artificial selection - the emphasis was that the processes were natural, undirected, with no intelligent designer overseeing the process; he took God's role away. Variation and heredity are the mechanisms by which natural selection can result in evolution, and are the key parts of the theory of evolution, but the shock to the system is that this needs no God Gleng 10:00, 6 July 2006 (UTC)
If we are serious about coming up with a good lead paragraph, I think that two things have to happen:
The alternative is continuing to argue continuously and pointlessly. Ted Talk/ Contributions 12:28, 6 July 2006 (UTC)
I'm sorry if I've seemd to be condescending, certainly don't feel that; i was just trying to explain the relative advantages of one position as I saw it; I agree that there is nothing to separate us in the core position, and probably nothing to separate us at all except in differences in how best to write this article clearly. At least we're keeping these discussions here not in the article. I've done my bit and am happy to withdraw now Gleng 16:08, 6 July 2006 (UTC)
I think the condescending remark is directed at my debate with Kim! Kim is right in that there does seem to be a slight shift in opinion over time. Just a word on my personal view as to why we have 2 definitons. I don't think the change is caused by greater understanding of inheritance, or other mechanisms of evolution. Nor do I think it's caused the introduction of the word 'evolution' into the English language. I attribute the change to historical misunderstanding of the original meanings of 'natural selection' and 'survival of the fittest', and a shift to a definition which is more friendly towards quantitative analysis, one which also lends itslef to making the kind of explanation Gleng was talking about above. Maybe Futyama plays a part by influencing people with his preference. — Axel147 16:51, 6 July 2006 (UTC)
After some thought, I think I pass on trying this, and I will follow the steps of Gleng in this case. -- Kim van der Linde at venus 19:33, 6 July 2006 (UTC)
The sentence in the overview is 'some traits are determined by just a single gene, but most are affected by many different genes.' But is this correct? Marcosantezana once said in this talk 'the fitness-wise most important phenotypic variation is either genetic but not heritable in the narrow sense or is not genetic at all'. Kim has expressed similar views in separating selection from response. — Axel147 13:59, 6 July 2006 (UTC)
The purpose of this sentence was to dismiss the idea that there is a one to one relationship (in general) between a gene (or an allele) and a single function (or trait). There isn't a "gene" for say "big muscles". but a huge number of genes, variation in which will have some effect on muscle growth, and in probably every case the variations will have other consequences too. So the sentence was a warning that the link between genetic vand phenotypic variation is not simple. It could be argued that there are no traits determined by a single gene, but this comes down to how you define a trait and what you mean by determined by. For example, in c elegans, mate seeking behaviour is said to be determined by a single gene because ablation of that gene eliminates the behaviour; however many other genes influence that gene so... If the point your getting at is that many phenotypic traits that affect fitness are influenced strongly by environmental and epigenetic factors and have no heritable component, then yes, absolutely right. Gleng 12:19, 7 July 2006 (UTC)
What I was trying to get at is is it possible to have a trait that is influenced by no genes at all? On second thoughts this seems impossible. (Even if a trait is taught or happens by some accident the capacity to be taught or have the accident must somehow influenced by genes.) — Axel147 15:30, 7 July 2006 (UTC)
I don't mean to be a pain in the ass but I feel pretty strongly that the word "environment" or "population" belongs in the first sentence. Can anyone come up with an elegant way to accomplish this? I promise, if all of you disagree with me, I will drop it. Slrubenstein | Talk 17:02, 7 July 2006 (UTC)
I have no abjection to this last paragraph by KimvdLinde. to respond to her earliest objections to my request, isn't it true that while selection may be sexual or act on individual organisms, it nevertheless acts on organisms or pairs within a particular environment, or part of a particular population? Slrubenstein | Talk 10:22, 8 July 2006 (UTC)
The more I read the first sentence, the worse it seems. What do we mean by "processes"? How pollen is distributed? Sperm mobility? I read this, and I immediately see biological processes. While those are differences are useful in natural selection, they are not the process of natural selection. Does Intelligent Design fit this first sentence (who says God isn't a process)? I won't even get started on encompass.
Unfortunately, it looks like a sentence created by a committee, "full of sound and fury, signifying nothing." Ted Talk/ Contributions 21:58, 7 July 2006 (UTC)
as I indicated, it is not my preferred sentence. -- Kim van der Linde at venus 22:07, 7 July 2006 (UTC)
as I also indicated, not my preferred sentence. I think it is better to emphasise the link between individual repoductive successs and traits. — Axel147 10:33, 8 July 2006 (UTC)
This was the version as of June 22. My impression was that this was a consensus version among Glen, Ted, Kim, Samsara, and Axel: "Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce." We can certainly just go back to it. The reason I started mucking with it was three-fold: first, NS is a differential process, so it isn't enough to say that some organisms survive and reproduce - they do so more than others; others surive and reproduce less; this is one major reason why I think it is important to specify that we are talking about individual members of a population. Second, while I agree 100% with Axel that traits should be included, the term "favorable" seemed tautological to me. We know that a trait is favorable because nature selected for it; sometimes we then need to figure out what made it favorable. True, sometimes it is obvious but once we assume it is always obvious we are on the road towards teleological arguments about evolution. Third, and a related point, is that traits are favorable only vis a vis something else which is why I wanted to include reference to the environment in which these organisms live. Can we address my three concerns and still have a consensus? Slrubenstein | Talk 10:43, 8 July 2006 (UTC)
This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
In response to a request from Ted I have now got hold of a copy of Fisher’s ‘The Genetical Theory of Natural Selection (1930)’. The title suggests Fisher considers inheritance to be a component of Natural Selection; that he uses the same definition as Darwin. Here is a (slighlty abridged) extract:
So Fisher uses Natural Selection in the Darwinian sense. I have updated my diagram.
— Axel147 08:51, 4 July 2006 (UTC)
In fact, neither Darwin, nor Fisher use natural selection in a single consistent sense; Fisher for instance does not include sexual selection as natural selection; now we would. Gleng 17:27, 4 July 2006 (UTC)
Wallace 1871, "On Natural Selection" uses Natural selection as Survival of the Fittest (p302, "meaning simply that, on the whole, those who die are least fitted to maintain their existence" quotng Darwin "Origin" chap III.)
This is clearly circular as a definition, but fine as a description. The circularity can be removed by defining natural selection as the natural processes of selection, as against the artificial processes used by farmers, in which case "Natural selection comprises the natural processes by which some individual organisms survive and reproduce while others do not."
The theory of natural selection states that, if there is heritable variation in a population, then when a component of selection is selection for a heritable trait, that trait will become enriched in the population, and adaptive evolution will take place. The confusion is between whether you use Natural Selection as a name for the theory, which clearly is a common shorthand usage, or strictly for the processes of selection. If you use it for the processes of selection, and seek to explain some effect by this, then it is essential to avoid defining natural selection by that effect, for then your argument will be vacuous. However, this article is not an academic article, and it's most important to be clear; I'd rather avoid well known traps Gleng 16:12, 28 June 2006 (UTC)
OK,:How is this mechanically different from defining natural selection as "Natural selection comprises the natural processes by which some phenotypic characteristics are preserved while others are not." This is fine as a description or characterisation of natural selection. To put the creationist argument bluntly, it is in part that the theory of natural selection is dogma not science, comprising unscientific (unfalsifiable) assertions. There is some validity in this because if we define anything by its effect, then we lose the power for it to explain that effect - and if we define natural selection in the above way, the statement that some traits are enriched in a population as a result of natural selection becomes tautological, unfalsifiable, and vacuous; it is simply an assertion of something true by definition, but which might be trivially true if the definition does not in fact apply to anything. If natural selection is defined in an open and simple way however, the same statement becomes a bold prediction and is falsifiable, and is true only when some sources of variation are heritable and when there is some component of selection for heritable traits. Gleng 16:11, 5 July 2006 (UTC)
Yes, it's true that I'd prefer a definition that makes this key argument easier to make, and yes I agree that the power of the theory isn't affected one way or another; as for using a different definition from Darwin - well Darwin said things in different ways at different times too, but I think the main sense in which he used natural selection is as opposed to artificial selection - the emphasis was that the processes were natural, undirected, with no intelligent designer overseeing the process; he took God's role away. Variation and heredity are the mechanisms by which natural selection can result in evolution, and are the key parts of the theory of evolution, but the shock to the system is that this needs no God Gleng 10:00, 6 July 2006 (UTC)
If we are serious about coming up with a good lead paragraph, I think that two things have to happen:
The alternative is continuing to argue continuously and pointlessly. Ted Talk/ Contributions 12:28, 6 July 2006 (UTC)
I'm sorry if I've seemd to be condescending, certainly don't feel that; i was just trying to explain the relative advantages of one position as I saw it; I agree that there is nothing to separate us in the core position, and probably nothing to separate us at all except in differences in how best to write this article clearly. At least we're keeping these discussions here not in the article. I've done my bit and am happy to withdraw now Gleng 16:08, 6 July 2006 (UTC)
I think the condescending remark is directed at my debate with Kim! Kim is right in that there does seem to be a slight shift in opinion over time. Just a word on my personal view as to why we have 2 definitons. I don't think the change is caused by greater understanding of inheritance, or other mechanisms of evolution. Nor do I think it's caused the introduction of the word 'evolution' into the English language. I attribute the change to historical misunderstanding of the original meanings of 'natural selection' and 'survival of the fittest', and a shift to a definition which is more friendly towards quantitative analysis, one which also lends itslef to making the kind of explanation Gleng was talking about above. Maybe Futyama plays a part by influencing people with his preference. — Axel147 16:51, 6 July 2006 (UTC)
After some thought, I think I pass on trying this, and I will follow the steps of Gleng in this case. -- Kim van der Linde at venus 19:33, 6 July 2006 (UTC)
The sentence in the overview is 'some traits are determined by just a single gene, but most are affected by many different genes.' But is this correct? Marcosantezana once said in this talk 'the fitness-wise most important phenotypic variation is either genetic but not heritable in the narrow sense or is not genetic at all'. Kim has expressed similar views in separating selection from response. — Axel147 13:59, 6 July 2006 (UTC)
The purpose of this sentence was to dismiss the idea that there is a one to one relationship (in general) between a gene (or an allele) and a single function (or trait). There isn't a "gene" for say "big muscles". but a huge number of genes, variation in which will have some effect on muscle growth, and in probably every case the variations will have other consequences too. So the sentence was a warning that the link between genetic vand phenotypic variation is not simple. It could be argued that there are no traits determined by a single gene, but this comes down to how you define a trait and what you mean by determined by. For example, in c elegans, mate seeking behaviour is said to be determined by a single gene because ablation of that gene eliminates the behaviour; however many other genes influence that gene so... If the point your getting at is that many phenotypic traits that affect fitness are influenced strongly by environmental and epigenetic factors and have no heritable component, then yes, absolutely right. Gleng 12:19, 7 July 2006 (UTC)
What I was trying to get at is is it possible to have a trait that is influenced by no genes at all? On second thoughts this seems impossible. (Even if a trait is taught or happens by some accident the capacity to be taught or have the accident must somehow influenced by genes.) — Axel147 15:30, 7 July 2006 (UTC)
I don't mean to be a pain in the ass but I feel pretty strongly that the word "environment" or "population" belongs in the first sentence. Can anyone come up with an elegant way to accomplish this? I promise, if all of you disagree with me, I will drop it. Slrubenstein | Talk 17:02, 7 July 2006 (UTC)
I have no abjection to this last paragraph by KimvdLinde. to respond to her earliest objections to my request, isn't it true that while selection may be sexual or act on individual organisms, it nevertheless acts on organisms or pairs within a particular environment, or part of a particular population? Slrubenstein | Talk 10:22, 8 July 2006 (UTC)
The more I read the first sentence, the worse it seems. What do we mean by "processes"? How pollen is distributed? Sperm mobility? I read this, and I immediately see biological processes. While those are differences are useful in natural selection, they are not the process of natural selection. Does Intelligent Design fit this first sentence (who says God isn't a process)? I won't even get started on encompass.
Unfortunately, it looks like a sentence created by a committee, "full of sound and fury, signifying nothing." Ted Talk/ Contributions 21:58, 7 July 2006 (UTC)
as I indicated, it is not my preferred sentence. -- Kim van der Linde at venus 22:07, 7 July 2006 (UTC)
as I also indicated, not my preferred sentence. I think it is better to emphasise the link between individual repoductive successs and traits. — Axel147 10:33, 8 July 2006 (UTC)
This was the version as of June 22. My impression was that this was a consensus version among Glen, Ted, Kim, Samsara, and Axel: "Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce." We can certainly just go back to it. The reason I started mucking with it was three-fold: first, NS is a differential process, so it isn't enough to say that some organisms survive and reproduce - they do so more than others; others surive and reproduce less; this is one major reason why I think it is important to specify that we are talking about individual members of a population. Second, while I agree 100% with Axel that traits should be included, the term "favorable" seemed tautological to me. We know that a trait is favorable because nature selected for it; sometimes we then need to figure out what made it favorable. True, sometimes it is obvious but once we assume it is always obvious we are on the road towards teleological arguments about evolution. Third, and a related point, is that traits are favorable only vis a vis something else which is why I wanted to include reference to the environment in which these organisms live. Can we address my three concerns and still have a consensus? Slrubenstein | Talk 10:43, 8 July 2006 (UTC)