Talk:Natural selection/Archive 6

This is an archive of past discussions about Natural selection. 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.

Archive 1

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Archive 4

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no article ban notice for Marcosantezana on this page? 02:35, 6 June 2006 (UTC)—Preceding unsigned comment added by 69.117.7.248 (talk • contribs)

Maybe because Marcos has not edited on Wikipedia for several weeks. Or, maybe that the arbitration case took so long to decide that everyone forgot. Why does it matter? Ted 02:51, 6 June 2006 (UTC)

The case has concluded. I think all editors are aware of the case, andnthe notice is just for the editors, not for him. -- Kim van der Linde ^{at venus} 04:23, 6 June 2006 (UTC)

alert

All of you who have worked hard to achieve this consensus improved version of the NS article should look at this: [1] Slrubenstein | Talk 21:40, 9 June 2006 (UTC)

I'm happy with it. I think the key points are evolution is an outcome which can be achieved by several mechanisms. It has to be change, change in something which could persist i.e. something not transient. The obvious candidates are phenotypic characteristics and alleles. I think to say changes in allele frequency is fair enough. Maybe other changes can persist such as changes in allele distribution rather than frequency, but I don't think I'm getting into that. — Axel147 09:37, 12 June 2006 (UTC)

Beware of selfish genetic elements

Although the phrase is still often used by non-biologists, modern biologists avoid it because it is tautological if fittest is read to mean functionally superior.

Depending on how exactly fitness and functionality are defined, the above could be incorrect. I was thinking about "usually" between "biologists" and "avoid", but it may need elaboration. Thoughts?

Samsara (talk • contribs) 00:52, 15 June 2006 (UTC)

I know that some of you don't think I'm a modern biologist, but I use the phrase some time during most semesters in my class. It is incorrect in any case, but it helps to drive home the concept of fitness. The reason it is incorrect is that being the "fittest" does not guarantee survival. I prefer to say something more like "survival in proportion to fitness," but when I do something like that the students' eyes roll back into their heads and they are asleep in seconds. I would not, however, use such a phrase with non-students. I don't avoid the phrase in general use because it is tautological, rather, I avoid the phrase because it is incorrect. Ted 01:30, 15 June 2006 (UTC)

I agree with Samsara (and also Ted). The phrase as it stands could be incorrect. To say 'the functionally superior tend to survive' is a valid observation not tautological. I suggest biologists avoid 'survival of the fittest' because this should be interpreted as the more long-winded 'tendency to survive and reproduce of the fitter'...(unless the phrase is intended to apply to lineages or characteristics rather than individuals!) — Axel147 12:10, 15 June 2006 (UTC)

I also agree with the statment above. Further this should say that natural selection is defined by an outcome. The process is a black box of ecological, neuroethological, and proteogenomic interactions that have not been clarified. I don't know of a definition that everyone would agree on in its strictest sense. Also the example of bacteria maybe a poor one given evidence that phenotyipc response and inhibition of division can also produce the same effect, and that horizontal transfer of genomic elements from soil bacteria with a huge reservoir of antibiotic resistance can also produce antibiotic resistance in clinical relevant strains.GetAgrippa 14:31, 29 August 2006 (UTC)

Agreed. It is a popular phrase - it even overshadows Darwinian thought - so I think the article is on the right track. I think we need to emphasize that the phrase is Spencer's, and not Darwin's, explain why so many people find it so appealing, and be very clear about what is wrong with it. Slrubenstein | Talk 12:19, 15 June 2006 (UTC)

Look at this quote from Spencer...

This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called "natural selection, or the preservation of favoured races in the struggle for life

So another reason to be careful with it as I said above in the brackets is confusion over whether it applies to individuals or 'races'. — Axel147 12:30, 15 June 2006 (UTC)

Just to add to the above a quote from Darwin rather than Spencer, Darwinian Natural Selection is not about survival of the fittest individuals. Individuals die — it is characteristics (or lineages) that may survive. As so many people seem to misunderstand this point here's the extended extract:

As man can produce, and certainly has produced, a great result by his methodical and unconscious means of selection, what may not natural selection effect? Man can act only on external and visible characters: Nature, if I may be allowed to personify the natural preservation or survival of the fittest, cares nothing for appearances, except in so far as they are useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good: Nature only for that of the being which she tends. Every selected character is fully exercised by her, as is implied by the fact of their selection. Man keeps the natives of many climates in the same country; he seldom exercises each selected character in some peculiar and fitting manner; he feeds a long and a short beaked pigeon on the same food; he does not exercise a long-backed or long-legged quadruped in any peculiar manner; he exposes sheep with long and short wool to the same climate. He does not allow the most vigorous males to struggle for the females. He does not rigidly destroy all inferior animals, but protects during each varying season, as far as lies in his power, all his productions. He often begins his selection by some half-monstrous form; or at least by some modification prominent enough to catch the eye or to be plainly useful to him. Under nature, the slightest differences of structure or constitution may well turn the nicely balanced scale in the struggle for life, and so be preserved. How fleeting are the wishes and efforts of man! how short his time! and consequently how poor will be his results, compared with those accumulated by Nature during whole geological periods! Can we wonder, then, that Nature’s productions should be far “truer” in character than man’s productions; that they should be infinitely better adapted to the most complex conditions of life, and should plainly bear the stamp of far higher workmanship?

It may metaphorically be said that natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages, and then so imperfect is our view into long-past geological ages, that we see only that the forms of life are now different from what they formerly were.

In order that any great amount of modification should be effected in a species, a variety when once formed must again, perhaps after a long interval of time, vary or present individual differences of the same favourable nature as before; and these must be again preserved, and so onwards step by step. Seeing that individual differences of the same kind perpetually recur, this can hardly be considered as an unwarrantable assumption. But whether it is true, we can judge only by seeing how far the hypothesis accords with and explains the general phenomena of nature. On the other hand, the ordinary belief that the amount of possible variation is a strictly limited quantity is likewise a simple assumption.

Although natural selection can act only through and for the good of each being, yet characters and structures, which we are apt to consider as of very trifling importance, may thus be acted on.

From the 5th edition of the Origin. —Axel147 23:06, 19 June 2006 (UTC)

As I have argued so many times in this page Darwinian Natural Selection is not the idea some individuals reproduce more than others; it is the idea that if you select characteristics some of them will be preserved. — Axel147 23:19, 19 June 2006 (UTC)

As an ignorant layman, may I suggest from the above that the article be amended to indicate that the term is avoided because it is misleading, as it really refers to selection of best fitted lineages leading to preservation of heritable characteristics? ..dave souza, talk 07:48, 20 June 2006 (UTC)

Well, while some biologists might avoid it anyway, its tautological nature makes it important to avoid it to be rigorous. The problem is simple - how can you objectively define functional superiority in this context except by differential reproductive success?Gleng 18:18, 24 June 2006 (UTC)

Yes, but a phrase such as ‘the functionally superior (or best adapted) tend to have greater reproductive success’ is still not tautological. We could imagine a world where this was not the case. This has explanatory value even if we have trouble measuring, defining or finding an independent criterion for ‘functional superiority’. — Axel147 20:10, 26 June 2006 (UTC)

No, I don't think so. If functional superiority is divorced from reproductive success then the statement ceases to become tautological but instead becomes false. Androgenised females may well be "functionally superior" in any sense that normal males are functionally superior, but they will certainly not tend to be reproductively successful. So for the statement to be true, then functional superiority has to be measured by reproductive success, and then it is tautological.Gleng 13:13, 28 June 2006 (UTC)

'Smokers tend to have lower life expectancy.' Surely this is true even if I can find the odd exception? So 'divorcing' need not make it false. For a relationship to be true it clearly doesn't need be tautological. Whether my phrase adds a lot of value is different question. —Axel147 08:41, 29 June 2006 (UTC)

rephrasing the first sentence

Currently:

Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce

I suggest something like

Natural selection is the process by which individual organisms with traits that are, within a specific niche, advantageous, are more likely to survive and reproduce thatn individuals lacking such traits or posessing disadvantageous traits.

I realize this is longer and more complex ... but isn't it much more precise and accurate? Slrubenstein | Talk 13:21, 28 June 2006 (UTC)

Well, it suffers from the same basic problem: what do you mean by advantageous if you do not mean that they are more likely to survive and reproduce. The creationist argument that this definition is circular and hence vacuous is hard to counter. It might not bother us particularly because actually we don't really try to use the definition in any deductive way, but I can see the point that if we extoll the scientific rigor and explanatory power of natural selection then we'd do well to avoid this problem, as we can do easily by defining natural selection as the totality of selective forces:

"Natural selection are the natural processes by which some individual organisms survive and reproduce while others do not."Gleng 16:12, 28 June 2006 (UTC)

The lead paragraph should be easily accessible by just about everyone. It should be easy to read and written in simple sentences. Moreover, we would do well to avoid having it sound too academic. I'd be inclined to leave out the "favorable traits" part, but I'm not sure how to do it without making the sentence unreadable. Ted^Talk/_{Contributions} 18:59, 28 June 2006 (UTC)

Natural selection is the process by which individual organisms with some traits reproduce less well than those with different traits.

This is all you can say without invoking heritability (which I understand is left out in the beginning because some interpretations of the meaning of "natural selection" do not include it).

Nota bene: early death is a subset of failure to reproduce. - Samsara (talk • contribs) 21:01, 28 June 2006 (UTC)

How about, "Natural selection encompasses processes by which some individual organisms survive and reproduce at greater or lesser rates, within a particular environment?" I won't quibble about including heritability in the first sentence, but it ought to be introduced 9as it is, i think) in the second sentence.

OR: "Natural selection is the process by which individual organisms, by virtue of posessing specific traits within a specific niche, are more likely to survive and reproduce than individuals lacking such traits or posessing disadvantageous traits." "Slrubenstein | Talk 09:15, 29 June 2006 (UTC)

The current first sentence:

Natural selection encompasses processes by which some individual organisms survive and reproduce at greater or lesser rates, within a particular ecosystem.

My concerns include:

Individuals either survive or they don't. There is no rate. You can speak of risk of survival (an interesting twist on words).
Is natural selection an individual concept (ignoring group selection and the such)? Or, a population concept?
Isn't the main idea with natural selection that it gives rise to genetic change? I don't see that here.
I'm still not sure what you intend with the reference to ecosystem. Migratory birds often cross many ecosystems in their flight. Are you trying to get at the point that natural selection reflects (to a greater or lesser extent) the environment the organisms experience?
I thought I had come up with another one on the bus this morning, but I don't recall it. If I do, I'll put it here. - Ted^Talk/_{Contributions} 13:48, 29 June 2006 (UTC)

In reply to Slrubenstein and in agreement with Ted, I think it would be prudent to steer clear of artificial constructs such as ecosystem and niche. - Samsara (talk • contribs) 17:47, 29 June 2006 (UTC)

Well, I do think it is an improvement over what we had before. I agree it is imperfect. About point 3, I think this should be covered in the the following setnences. Do you think they are? If not, how would you do so? Either way, I think the issue of heredity must be made in the first paragraph but not the firswt sentence (for brevity and clarity sake). How about

Natural selection encompasses processes by which individual organisms constituting a population survive and reproduce at greater or lesser rates?

Slrubenstein | Talk 10:02, 30 June 2006 (UTC)

Worker bees

I have a question. With this type of definition how should I interpret the case of worker bees? Should I conclude worker bees are not subject to natural selection (as they cannot reproduce) or that they have extremely unfavourable traits? (Or maybe they should not be considered 'individuals' but extended phenotypes of an individuals that can reproduce?) — Axel147 09:03, 29 June 2006 (UTC)

(Axel, I moved your question here because it is an important question and should be the focus of its own discussion. It gets at the question of whether evolution and selection operate at the level of the gene, the individual organism, or the population, and is an issue that should be addressed at some point in the article. I just think we should keep it separate from the matter of the first paragraph, which should be as simple as possible. Slrubenstein | Talk 09:34, 29 June 2006 (UTC)

Axel's bee question is a good example of many difficulties that arise; it can be avoided in this case by a redefinition of an individual, or avoided altogether by simply using the natural language definition, that natural selection embraces all naturally occurring processes that determine which individuals will reproduce.

The problem with Slrubenstein's second suggestion, which excludes "accidental" elimination of individuals is that it is difficult if not impossible ever to tell whether an individual has survived by good fortune or by some advantage that it possesses, although it is possible to infer that these advantages must indeed have been influential over huge amounts of time. Again, I am anxious to stress that selection for beneficial heritable traits is normally a tiny force in any generation; typically most individuals that are born alive survive or fail to produce through sheer chance. Creationists have a problem with understanding how almost imperceptible differences of phenotype can lead to differential reproductive success and hence evolution, because it goes against all our experience; the answer is that scarcely perceptible differences give only a very tiny advantage, but given enough time then such advantages will tend to be enriched in the population. It is the immensity of time that explains why selection for heritable variation can be effective, not its potency in any one generation. Slrubenstein's first suggestion is fine.Gleng 09:56, 29 June 2006 (UTC)

Social insects only create a problem with people who feel the unit of selection is always the individual. If you take a Dawsonesque view of things, then social insects are just one of the various ways that genes use to increase their own kind. Taking a population-view of things leads to much the same conclusion — the strategy is unusual, but it still leads to an increase in allele frequency, indirectly through the reproductive success of the queen. Ted^Talk/_{Contributions} 13:56, 29 June 2006 (UTC)

Since only the queen is reproducing, the individual still is the unit of selection - selection can't very well be in operation if you produce no offspring.

As to Gleng's "immensity of time" comment, this is relative. In human populations a new mutation with selection coefficient of 1e-3 should reach fixation in about 18,000 generations - a long time, but not necessarily "immense". In Drosophila, with a generation time of 4 days, a similar mutation might fix in ~300 years. Graft 17:00, 29 June 2006 (UTC)

One of the problems with the concept of unit of selection is that regardless of how you choose it, you can always reparameterize the problem to answer questions about rate, etc. The interesting part of social insects is that the "health" (dare I say, "fitness"?) of the hive is dependent on the workers. It is haplotype selection, which brings into it a measure of linkage (unusual in our normal discussions of selection). For example, a queen might be doubly heterozygous for simple Mendelian deleterious traits. For normal individual selection, it doesn't matter whether she is AB/ab or Ab/aB. For the queen, if she is AB/ab, then she is producing more AB haplotypes than if she is Ab/aB, which can have a profound effect. So: gene selection? individual selection? hive selection? Ted^Talk/_{Contributions} 17:56, 29 June 2006 (UTC)

Question: does this article already adequately address this? If not, how and where should it? Slrubenstein | Talk 13:57, 29 June 2006 (UTC)

It is an interesting question, and one that might deserve its own short article; as Ted says if you consider the gene as the unit of selection there is no problem, and maybe it could be inserted as an example of how considering different levels of selection can help understand particular examples. There is still a problem here though of alligning fitness with the account of selection - when we are talking of the individual as the unit there is no problem as we can talk of the fitness of individuals and selection of the most fit indiduals, for ants we have to talk about selection in a much more convoluted context (selection of the drone, of the queen, of the hive, and selection at the level of genes), so I don't know that it is easy to explain this concisely, but it would be interesting to see someone try.Gleng 16:18, 29 June 2006 (UTC)

My sense is that there have been some (studies or theorists, your pick) that focus on the level of the gene, others who look at the organism, and others who look at the species. If I am right, our task is not to arbitrate which approach is correct, but to explain to our readers that there are these three approaches, explain why people take different approaches, and explain the extent to which each approach has different consequences for our understanding of natural selection (or evolution). If this approach makes sense, then thing to do would be to set up a general section with room for each of the three approaches, and then invite people to work on whichever subsection they know most about. Slrubenstein | Talk 10:05, 30 June 2006 (UTC)

Well yes. But I don't think there's a big debate here. I think everyone is in agreement that the most important form of natural selection, the form which does result in adaptive evolution of individuals, is natural selection acting on individual phenotypes. (I think this can be phrased in two equivalent ways 1. selection of properties which benefit individuals 2. selection of individuals with beneficial properties.) Have a look at Burying the vehicle — Axel147 13:37, 30 June 2006 (UTC)

I don't doubt you about "the most important form" but this is relevant only to how we introduce the article and the weight we give to this form - and I do not think anyone is being argumentative about this. I think we are all in agreement as to what the most important form is, and I think the article as it stands reflects that agreement. I am suggesting only that we have a section summarizing the other forms and what is at stake in these different forms. Wouldn't that make this a more interesting and informative article? It could either be ia new item 4.3, Object of selection, or a new item nine, debates over the object of selection, or 9.1 the gene as object of selection (I am thinking Dawkins) and 9.2 the species as object of selection (Gould, I am thinking). I don't think these kinds of additions should be controversial or would disrupt what we already have. Slrubenstein | Talk 13:59, 30 June 2006 (UTC)

I agree; the issues around the level of selection are very interesting, and if we can find a recipe for introducing these without getting bogged down in disputes or excessive detail it would be good. One way might be to discuss selection at the gene level and selection at the group or species level just by explaining particular examples where thinking of selection as acting at these different levels might help in understanding some particular cases. This might be a non-controversial strategy if we can avoid being assertive - some will argue that all selection can be explained wholly at an individual level or wholly at the gene level, while others are unconvinced that these explanations are clear or persuasive or exhaustive, but if we just look for examples that seem to be most clearly explained at a different level without arguing that this is the only possible explanation, we might find a path through, i.e. to use examples to explain what is meant by selection at the different levels. Certainly Gould's ideas merit explanation, although mainly this should be by linking to an article on Gould, which itself needs a lot of work. Unfortunately I don't have much time myself to help out at present.Gleng 14:17, 30 June 2006 (UTC)

May I suggest that the first issue is to decide where - 4.3, or a new 9.1 and 9.2? Then it is a simple matter of complying with NPOV. Slrubenstein | Talk 14:20, 30 June 2006 (UTC)

It could be added after the Modern Synthesis - this is an area of current debate, after all, and perhaps the positioning should reflect thisGleng 19:31, 30 June 2006 (UTC)

I would like to stress that when I came up with the worker bee question I wasn't trying to introduce group selection ideas. I was wondering if the opening statement about individual selection could be improved. (I think Darwin's definition avoids this problem.) We can consider different properties of an individual

Capacity to reproduce
Capacity to propagate charactertistics/genes

The worker bee is an extreme example where these are different: it can only propagate its characteristics by helping another individual to reproduce. Imagine our bee has dodgy trait that results in it flying in circles. Will the trait tend to eliminated by natural selection? Well, yes (unless correlated with a beneficial trait). And is it necessary to invoke a group selection explanation? No it isn't.

Although the trait has no effect on the worker bee's fitness (it remains zero) it does affect the fitness of the queen. The genes of the queen are correlated with those of the worker bee. So differential reproduction of queens explains evolution of the worker.

It might be helpful to view the worker as an extended phenotype of the queen. From the queen's perspective it is being selected for the trait of being surrounded by workers that do not fly in circles. — Axel147 11:09, 1 July 2006 (UTC)

Axel, with all due respect, it doesn't matter whether you intended to introduce the idea of group selection or not. You are welcome to make suggestions for improving the introduction, and there is a separate section on the talk page for that. But whether you intended it or not, the only question here is, would adding a section on this improve the article or not? If there are evolutionary scientists who have discussed this issue, then I think the answer is yes. Are you actually objecting to adding a section on the object of selection (gene, organism, or group)?

Also, as to "It might be helpful to view the worker as an extended phenotype of the queen." you may be right - but if this is your idea, then we cannot put it into the article, that would violate NOR. The question for improving this article is, (1) how have published scientists addressed this, (2) is what they have to say relevant to "natural selection" and (3) if so, where in the article should it go. Slrubenstein | Talk 11:35, 1 July 2006 (UTC)

Yes the group selection question is very important. I didn't mean to say otherwise. The question I was trying to ask was if sterile workers can be explained by individual selection does the article need to be enhanced to explain how? I hadn't got as far as proposing a change, wasn't trying to violate NOR. The bee question is related to group selection and I would also welcome a section on group selection. You are right to ask what scientists have published on this. Here is Sober's view (which I agree with) in The Nature of Selection p348:

We therefore have an answer to the question raised about Darwin's analysis of sterile castes in the social insects: If colonies are founded by a single female and disperse after her offspring mate with each other, then it will be equally true that there is selection for females who produce sterile castes and that there is selection for colonies that contain sterile castes. The conflicting images of group and individual selection fuse into one in this special case.

— Axel147 22:15, 2 July 2006 (UTC)

Selection and heritage

Excuse me for stating the obvious, but how come if we constantly go through "selection" (selecting better and better genes) all this time we never lost gene heritage (meaning we still have our common genes with our predecessors). When I review evolutional taxonomy it seems more like gene appending than gene selection, plus in biology books "evolutional taxonomy" is described as "common ancestry" and "extent of divergence" !!! In other words if we really went through "selection", how come species have "Phylogenetic tree". - cyber_indian 70.127.191.115 18:20, 3 July 2006 (UTC)

This understandable confusion is a result of a common laxity with language. All of our genes in a sense are shared with most other animals - 80% of our genes have homologues in Drosophila. However these genes are not exactly the same, the same gene in two species will generally have many slight differences. Of course no two individuals have exactly the same genes in the same sense as this - some genes differ slightly between individuals, but inter-individual differences are much smaller than inter-species differencesGleng 17:32, 4 July 2006 (UTC)

There is no confusion, we're taking about genes - CDS. Not transposons, repeated DNA or other non-CDS DNA. As we know DNA and RNA degradation happens all the time, fortunately we have also DNA repair mechanisms and probably also one of the reasons we have pair of chromosomes and sex - so we can always have source of one good gene copy. Sometimes genes didn't get repaired, but the difference is either not-fatal or the functionality stays intact (as is the case with the anti-AIDS gene in chimps and humans - non-fatal). I believe the confusion comes when we're talking about DNA testing - which is done by mapping self-repeating DNA - got noting to do with CDS. So if gene had survived delsDNA degradation and didn't get fatal or in overall didn't change it's functionality - it became homologous. Talking about difference - DNA in a single individual is never 100% the same in all his cells - because of that DNA degradation. And still what about the question of "losing predecessors trace". cyber_indian 70.127.191.115 18:33, 4 July 2006 (UTC)

It's funny how you always go around silently from the obstacles of the natural selection theory and always speak about the things you thing you understand. cyber_indian 70.127.191.115 08:02, 10 July 2006 (UTC)

Transposons are usually called jumping DNA. Microsatellites (used in DNA testing) are not transposons. Genes that are lost in the course of evolution are not available to be used in phylogenetic studies. - Samsara (talk • contribs) 21:09, 10 July 2006 (UTC)

Honest mistake, that wasn't meant for that sentence. Anyways lost genes - that's the mechanism by which organism shed it's unused genes or old genes that suffocate the working process of the newly added ones. Anyways very small numbers of genes get that honor. And still phylogenetic studies don't mention any alienation of species - it's all connected according to them. cyber_indian 70.127.191.115 18:34, 13 July 2006 (UTC)

Err. I'm not sure I understand you, here - so, maybe in one lineage a gene gets lost - there's still tons of other genes in common. Plus, some genes are simply never going to be lost, they're just too important, and one can always trace phylogeny through those... what exactly is your point? Graft 18:40, 13 July 2006 (UTC)

If it's a "natural selection" how come genes didn't perfected themselves into totally new ones and in this way totally alienate/lose heritage with it's predecessors. BTW you're kind of supporting my point. cyber_indian 70.127.191.115 19:06, 13 July 2006 (UTC)

Um, because there simply isn't that much selective divergence, usually. Let's say some new function is selected for in the active site of a protein - it's exceedingly likely that this "new" protein will still have enough common sequence in other parts (e.g. structural components of the protein) to maintain orthology with divergent proteins. It's a "new" gene, but it's still recognizably similar to the ancestor. Kind of like when I make a revision to a Wikipedia article - it's a "new" revision when I'm done, different from the previous one, but you can still tell that one is derived from the other. Graft 19:42, 13 July 2006 (UTC)

@cyber_indian

There simply hasn't been that much time. For example, the probability of a neutral mutation fixing is 1/2N; this process takes 4N generations from when the mutation first appears, where N is the population size, and results are for diploid organisms (sexual organisms are mostly diploid). The mutation rate is on the order of 10^-7 per gene for most organisms, so you can see the size of the problem! The fact that proteins are not completely exchanged basically comes down to the fact that good spellchecking genes reproduce faster than bad ones (because they "lose" fewer offspring to copying mistakes), and that life on our planet is very young and probably severely bottlenecked. - Samsara (talk • contribs) 19:55, 13 July 2006 (UTC)

In fact, I should concede that in comparisons between, say, bacteria and archaea, we have to resort to looking at some of the most basic genes, a small subset of the genes that those organisms have, in order to find the signal of their common descent. This set of genes would, for example, include genes coding for ribosomal and transfer RNAs - crucial genes whose malfunction would seriously curb the ability of an organism to produce proteins, let alone reproduce at a competitive rate. - Samsara (talk • contribs) 20:02, 13 July 2006 (UTC)

Graft - most of the genes use single CDS, but sometimes they're spread in few smaller CDS after that they are on their own. The way you describe it all genes are chain-interconnected. Samsara - How many light years will be enough ??? wasn't the time a single cell evolved into multi-cell enough ? Yeah what about tRNA and rRNA, why they didn't naturally select into higher revision ? Instead they stayed the same. P.S. although it's a different subject I believe that bacteria and eucariota derive from archaea, but because that contradict to natural selection probably I'm the only one that believe that. cyber_indian 70.127.191.115 21:16, 19 July 2006 (UTC)

So if we tell you that you're wrong again, will you once again tell us that you meant the right thing all along? - Samsara (talk • contribs) 21:36, 19 July 2006 (UTC)

You're unbelievable, well at least you believe you know what you're talking about. I'm sorry if I'm interrupting your philosophize, but nothing you said prove anything. cyber_indian 70.127.191.115 21:56, 19 July 2006 (UTC)

That's the difference between us. You're trying to prove something. I'm not. - Samsara (talk • contribs) 21:59, 19 July 2006 (UTC)

That's right you were telling me I'm wrong, you wasn't try to prove it. Well if you're not discussing why are you wasting space ? cyber_indian 70.127.191.115 22:04, 19 July 2006 (UTC)

Why not submit your research to a peer-reviewed journal? If you stick with the editorial process long enough, you'll end up with a manuscript that people can understand. Regards, Samsara (talk • contribs) 22:13, 19 July 2006 (UTC)

Is that mean you're kicking me out, and I can't discuss anything here ? Anyway I don't want to publish anything yet, I just want to discuss it. cyber_indian 70.127.191.115 22:19, 19 July 2006 (UTC)

All I'm saying is that a) I wish I could understand what you're getting at (because I honestly can't), and b) I wish I had the confidence that you'd checked your facts sufficiently to feel that it's worth continuing to discuss with you. Because if this is to be a free tutorial for you, I'm not up for it. Try the science helpdesk for that. - Samsara (talk • contribs) 22:26, 19 July 2006 (UTC)

What's so hard to understand, if natural selection was really happening we would have been so transformed from each other that even the rRNA wouldn't be the same. Every single gene or feature would be way different. I don't say that Darwin wasn't right about evolution, but even he was having second thoughts. cyber_indian 24.173.125.42 06:31, 23 July 2006 (UTC)

This page is not a forum for general discussion about Natural selection/Archive 6. Any such comments may be removed or refactored. Please limit discussion to improvement of this page. You may wish to ask factual questions about Natural selection/Archive 6 at the Reference desk.

— Knowledge Seeker দ 07:05, 23 July 2006 (UTC)

New lead sentence

The new lead sentence:

Natural selection encompasses processes by which individual organisms constituting a population survive and reproduce at greater or lesser rates.

is incorrect. There is no need for an organisms to be in a population, a single individual (the last one of a species for example) can be selected for (maladapted to a new world, the species goes extinct), just as can genes etc (see unit of selection). -- Kim van der Linde ^{at venus} 07:00, 4 July 2006 (UTC)

I don't understand that. Natural selection is differential survival and reproduction. With a single individual, there is no differential. Ted^Talk/_{Contributions} 15:03, 4 July 2006 (UTC)

Differential reproduction is the genetisists/stateticians definition which makes it possible to detect natural selection, but it fails like many of the discipline specific definitions to be general enough. -- Kim van der Linde ^{at venus} 15:07, 4 July 2006 (UTC)

I disagree. With only a single individual, there is no selection. Only death (or not). Ted^Talk/_{Contributions} 15:18, 4 July 2006 (UTC)

Well, you can have the selection of a single individual. When it is well adapted to the selection regime, it survives, when not, it dies. There is no problem with that. The problem arrises when you want to quantify the strength of the selection, you can not do that on an individual, but that is a statistical problem hence the statistical definion that statesticians love but is slightly inaccurate. -- Kim van der Linde ^{at venus} 16:18, 4 July 2006 (UTC)

Actually, statisticians are interested in estimation. The case you present is similar to a Spartan Square (a 1X1 Greco-Latin Square, which has statisticians rolling in the aisles with laughter). Estimation is entirely different from parameterization. What selection "regime" for a single individual? Are you discussing artificial selection? What happens when it is the best possible genotype/phenotype, but dies anyway? It seems like you are trying to define natural selection without reference to the parameters. Ted^Talk/_{Contributions} 17:14, 4 July 2006 (UTC)

If I were discussing Artificial selection, I would be doing that here. Natural selection can be studied using statistics, but that nessecarily includes simplifications, such as sufficient large population sizes to get to estimations, and to parametrize the models they use. When the fittest individual dies anyway, it was apparently not fit enough (unless there is a pure random process going on, in which case it is not natural selection to start with). If that were not a possibility, natural selection could not result in extinction of species. And the 1X1 Greco-Latin Square is a perfect example where statistics fail when biological prosecces are still present. -- Kim van der Linde ^{at venus} 17:41, 4 July 2006 (UTC)

Separate point

Natural selection encompasses processes by which individual organisms constituting a population survive and reproduce at greater or lesser rates.

or

Natural selection encompasses processes by which individual organisms reproduce at greater or lesser rates.

How is this different from simple population growth? Different populations survive and reproduce at high rates, or low rates. How is this excluded from the definition? Ted^Talk/_{Contributions} 17:18, 4 July 2006 (UTC)

Is a species is well adapted, population growth is a logical consequence. And that is why the old lead sentence was better AFAIC. The new sentence does not do a good job to get to the finesses. -- Kim van der Linde ^{at venus} 17:45, 4 July 2006 (UTC)

This sentence?

Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce.

Ted^Talk/_{Contributions} 19:25, 4 July 2006 (UTC)

Yes, it is not perfect, but at least better. -- Kim van der Linde ^{at venus} 21:04, 4 July 2006 (UTC)

More likely than what? It is meaningless without a reference population. Ted^Talk/_{Contributions} 21:58, 4 July 2006 (UTC)

As an (hypothetical) individual that is less adapted, and as such, you do not need a reference population. As I said, it is not perfect, and could be improved. -- Kim van der Linde ^{at venus} 00:05, 5 July 2006 (UTC)

OK, thanks. It is going to be hard to improve the statement with all the constraints. I don't seem to think that way. Ted^Talk/_{Contributions} 00:31, 5 July 2006 (UTC)

I think it is very possible to improve it. -- Kim van der Linde ^{at venus} 00:59, 5 July 2006 (UTC)

I agree with Ted there has to be a differential. Even if there were two individuals (the last 2 of a species) but they had identical fitness there would still be no natural selection. The amount of offspring they produce is still selected by nature but this is not 'natural selection' as this seems to be defined by the 'effect' of differential reproduction. — Axel147 22:47, 5 July 2006 (UTC)