Talk:Natural selection
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What does this mean:
- the best explanation of speciation
If speciation is the instance of a new species coming into being, then natural selection is not a mechanism of speciation. It is rather the process that determines whether and how long the species population survives. --Ed Poor
So what is missing from the wikipedia entries on Darwin's theory of evolution is (a) identification of the process(es) by which an instance of a new species initially comes into being and also (b) distinction between this(these) cause(s) -- controversial -- and how well they survive -- not so controversial.
I'd also like to see a more clear separation between (a) Darwin's philosophical arguments and (b) the science. -- Ed Poor
- I made a start on that by carefully distincting ecological from sexual selection. That makes it much clearer what Darwin thought "natural" (the combination of the two in his undifferentiated process where both matter) - also the post-Darwin observations and extreme conditions (where ecological or sexual factors are drastically unbalanced) are now covered mostly in ecological selection and artificial selection.
Someone authoritative, like a scientist, please tell me whether Natural Selection (NS) is only (A) a weeding out process whereby AFTER a new species comes into being it survives or perishes or only (B) a process whereby new species originate; or if A causes B, or if NS = A + B. I'm not trying to be cute some of the articles imply one thing, some another, and I can't write Intelligent Design objectively unless I know precisely where it differs from accepted scientific theory. Ed Poor
Seems I recall someone telling me in early Dec 2001 that the following (which appears in the first paragraph) is not true:
- Natural Selection indicate how new species come into being, how they survive, change or perish.
Shouldn't it be rather:
- Natural Selection does not indicate how new species come into being, but how they survive, change or perish.
The change I propose (if LDC and other scientists agree) allows Natural Selection to be compatible with Intelligent Design while the existing sentence is causes difficulty. -- Ed Poor
I would say that the term "Natural Selection," per se, only implies that some natural force is selecting certain individuals in a species, and is to be contrasted with artificial selection, where humans either on purpose or by accident select for certain traits. However, the modern Theory of Evolution is not just natural selection. it is natural selection plus random change by genetic mutation. Of course, that's a wild oversimplification, but I think it generally gives you what you want here. --Alex Kennedy
I'm sure "Natural Selection indicates ... how they change" would mean to eventually change in to a new species? -- sodium
- If I understand you correctly (and if LDC agrees), then it not Natural Selection per se but rather the theory of evolution which "indicates how new species come into being, how they survive, change or perish". The theory of evolution includes natural selection as the mechanism whereby after new species come into being or change they "survive or perish". Is this right, LDC, and may I change the evolution, theory of evolution, and natural selection articles to reflect this distinction? --User:Ed Poor
That's generally right, but it's not quite that simple. Let me work on those articles and see if I can clarify them better. --LDC
The prose in "Natural selection" was a bit sloppy, so I tightened it up a bit. The other articles, though, Evolution and Theory of evolution, seem fine to me. They don't go out of their way to make a distinction between the "mechanism" of natural selection as narrowly construed, and the modern overall theory of natural selection which includes mutation, etc.; but then scientists don't often go out of their way to make that distinction, because it's not usually important. The Natural selection article probably should, and does; but the more general ones should remain general. Making the fine distinctions is something that only seems important to you (and perhaps other ID folks), and my understanding of the issue is only mine, so I don't think either one belongs in the major articles. --LDC
I removed this:
- Perhaps the most radical claim of Darwin's theory of evolution through natural selection is that a set of random processes (including genetic mutation and natural disasters) can produce order. It is this fundamental claim that has inspired some of Darwin's most ardents supporters -- and that has provoked the most profound opporition. Some groups prefer to believe in divine intervention or guidance of the process; this is the "Intelligent design" school of thought.
We've already had this discussion: calling natural selection "random" is not only false, it is the 180-degree opposite of the truth, and has no place here. Mutation is random, selection is totally 100% deterministic. Every single one of your ancestors, without exception, was fertile, survived into pucerty, and chose to reproduce. Nothing random about that at all. --LDC
I rewrote the passage and re-inserted it. I did not originally write that "natural selection" is random, just that it involves random processes. Indeed, the original text refers to "non-deterministic" forces. In any event I trust that the current form is less controversial.
"Determinism" has been used in so many different ways I would hesitate to call even natural-selection "totally 100% deterministic." I'll grant that one can take natural selection as deterministic, but Darwin is clear that it is deterministic only in an immediate and local sense.
Please note too that I did not write the last sentence ("Some groups prefer..."); indeed, my contribution was meant to frame this sentence.
The bigger issue is that NOT every single one of my ancestors "chose" to reproduce, at least not in the same sense that you and I have chosen to discuss natural selection. If Darwin is right you and I share a one-celled organism as an ancestor that was not conscious (at least the way we are) and did not make choices (at least in our sense of the term. And I think this is what is at stake in the debate between Darwinists and Intelligent Design advocates -- whether the existence of consciousness today required a conscious creator (or designer). So I think it is important to recognize that Darwin's theory does not require such a principle. If someone else can find a more effective and accurate way to convey this I look forward to reading the next revision. -- SR
"Deterministic" is probably not the right word. Of course Darwin does not posit that 100% of your ancestors chose to reproduce, but he does posit that 100% of them did, in fact, reproduce; and that this feature distinugishes them from the 99.99% of all organisms throughout history that did not. Anything that's "100%" is not, by definition, random. Selection is immediate, precise, an brutal. And the reasons one animal reproduces and another does not are not entirely random--there are genuine differences, and those differences change the odds.
Your version is much better. "Random" is a fighting word. :-). --LDC
<thaw>Nice work on this article 24 -- maveric149, Sunday, April 14, 2002 </thaw>
- I'm trying - continuing my habit of tackling only controversial topics - contrary to popular belief this is to draw fire and attention to these topics not to gain undue influence for my views on them. But, don't thank me yet, the more controversial material is in ecological selection and artificial selection and I'm sure there'll be questions about it. As I noted above in my response to Ed Poor, it seems to make sense to keep "natural selection" and "sexual selection" as close to Darwin's sense as possible (natural including sexual), and to keep the more modern observations and differentiations with the other names (to my knowledge Darwin did not refer directly to artificial or ecological by name, they are artifacts of more recent distinctions made by modern biologists and sociobiologists and such)
I too appreciate your work on this article. I worked on it in the past -- you even changed some of what I wrote. But, for the most part, I think what you did is a real improvement. By the way, almost all of my criticism of your other owrk is that it is poorly written. I know you think others are opposed to you on ideological grounds, but even there I suspect that the real issue is clear prose that uses familiar terms when they exist, and always explains ideosynratic uses of old terms, or the use of relatively new terms, clearly. This is my main criticism of your entry on Artifical Selection, since it seems to me like old Baldwinian evolution and I wonder why you ignore that. Anyway, good job, here, SR
Is "directional selection" really a "mechanism" of natural selection? Isn't the whole point of natural selection that that it always favors adaptive traits?
- Natural selection favors the increasing fitness of a population, which may not necessarily be "adaptive" especially in the presence of strong epistatic interactions. There are several examples in population genetics where you get the counterintuitive behavoir that a population can actually lose an "adaptive allele" if there is enough drift, epistasis, or there is frequency-dependent effect (see below), because the meaning of adaptive can change with time. Lexor|Talk
What form of "natural selection" is not "directional?" I know that biologists use the term "directional," but I always thought that they used it somewhat colloquially, so general audiences understood the import of natural selection -- OR in order to develop precise mathematical models of specific directions in evolution. In this case, "directional selection" is at best a way of describing natural selection or a form of natural selection (sill want to know the other forms), not a "mechanism." Slrubenstein
- Directional selection has a precise meaning in population genetics, and it is a mechanism. It occurs when a single allele is favored over all others. It is to be distinguished from balancing selection (which includes both overdominant selection and frequency-dependent selection, both are modes or mechanisms that allow multiple alleles to be maintained in a population). In this sense it can be thought of as a "mode" of natural selection, but overdominance, frequency-dependent and directional selection are also mechanisms in the sense that the underlying relationship between the genotype and the fitness of the resulting phenotype will determine what kind of natural selection is in operation. Frequency-dependent selection will operate when there is some of kind of coevolution, for example in host-pathogen dynamics, a rare protective mutation in the host will be protective until the pathogen has adapted, this means that the selection coefficient (i.e. the "fitness") of a particular allele will actually change with the frequency that allele. Overdominance acts when the fitness of the heterozygote is higher than the two homozygotes. Both of these modes have the opposite effect on the allele frequency spectrum (or histogram) to directional selection, they "balance out" or make the allele frequencies more "even", whereas directional selection will always increase the frequency of one allele. --Lexor|Talk 15:31, 21 Apr 2004 (UTC)
- Thanks. I find this explanation much more helpful than what is in the article, although others may think it is too detailed. Do you think what you wrote (not just concerning directional selection but concerning mode vs.mechanism) should be in the article itself? Slrubenstein
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Early proposals of Wells and Matthew
I've added back the reference to Wells and Matthew, with references this time. They really deserve mention in the article, and separate articles of their own, too. Even Darwin admitted in "An Historical Sketch", which he added to later editions of The Origin of Species, that they thought of natural selection before he did, although Wells' applied it "only to races of man, and to certain characters alone," while Matthew "clearly saw...the full force of the principle of natural selection." Gould describes both proposals as "evolutionary."--Johnstone 02:52, 3 Nov 2004 (UTC)
- Right, we have http://www.talkorigins.org/faqs/precursors/precursnatsel.html which claims that Darwin read neither. I think these need mentioning, but not in the lead because it just confuses things. The point is that Darwin took his ideas from others, but provided the first coherent synthesis of evolution. Dunc|☺ 11:55, 3 Nov 2004 (UTC)
- I agree that a separate section is a better better place. I didn't mean to imply that Darwin plagiarized the idea. It's pretty clear from anything I've read that he was completely unaware of the earlier work. Actually, much of his work was quite original.--Johnstone 01:56, 4 Nov 2004 (UTC)
Edit
"To be precise, natural selection is not truly a "mechanism" in itself, as opposed to something like gravity. Instead, natural selection is the result of genetic and environmental forces acting upon an organism." I think this depends on your definition of mechanism. So it might be better to say something along the lines of: "To be precise, natural selection is not truly a "mechanism" in itself, at least not in the same sense as gravity is. Natural selection is the result of genetic and environmental forces acting upon an organism." GWC Autumn 68 ce 2004 15.10 EDT
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I also am concerned about the current language: "It is important to note that the term 'natural selection' is often used in the inaccurate yet fairly harmless metaphorical sense as having causal status...natural selection is not truly a "mechanism" in itself..."
Who wrote this? Let's be aware that this definition contradicts modern expert opinion. For example, the Penguin Dictionary of Biology (10th edition, 2001)-- which I realize is copywrited material, and so cannot be used on the Wikipedia page, but still (I hope) may be referred to here as an authoritative source -- defines "natural selection" as "(the) most widely accepted theory concerning the principal causal mechanism of evolutionary change...".
I propose that either someone should please stand up and take responsibility for the Wikipedia "important note" with a better defense, or else that note should be removed. It's certainly confusing when the reader encounters a section called "Mechanisms of NS" after seeing that it's "not truly a mechanism". IMHO, the IF-THEN statements are indeed mechanistic logic.
--Brad
Note
Is is true that Natural Selection is the only process whereby higher order and sophistication can be attained out of randomness (ie, no designer)?
So when people say Natural Selection can't be true because something as sophisticated as life as we know it couldn't have possibly have risen out of chaos, they're forgetting that's what the whole theory's all about.
GWC Autumn 68 ce 2004 15.15 EDT
Most biological sciences reject words like "sophistication" as species-centric. The Darwinian oncept that is relevant is fitness, and who is to say that we are more fit than bacteria? (Unless, you meant by "higher order" all life. I certainly think bacteria and I are both more sophisticated than rockes. But I don't know what rocks think -- and I am not in any rush to conclude that, if I don't know what rocks think, it is their fault). Slrubenstein
The theory is about the origins of species -- not the origins of sophistication. Slrubenstein
Article should be merged
With Selection ?