Natural selection past the reproductive age

Discussion in 'Biology & Genetics' started by spuriousmonkey, May 17, 2004.

  1. paulsamuel Registered Senior Member

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    It's not my definition. I agree with the definition you posted which I assume is from a dictionary.

    As I said, we agree on the altruism definition. You don't appear to understand the relationship between reproduction, fitness, and benefit.

    Longevity is meaningless unless it leads to more chances for reproduction. Consider a suite of genes that will enhance longevity at the cost of reproduction, i.e. individuals can live longer if they don't reproduce. How long do you think those genes will last in a population? One generation! Once those individual carriers are gone so are those genes. Genes like that can't evolve because the carriers don't reproduce! Their fitness is ZERO!

    The question is, how can altruistic traits evolve in a population? How can a trait that sacrifices one's fitness to increase the fitness of another, evolve? Answer, if the benefit to the sacrificer's fitness is greater than the fitness cost of the sacrifice. This is the only way!

    I don't. I conclude that because you said, "It is not incomplete because genetic propogation has nothing to do with benefits for the individual. There simply is no benefit there," and "One's fitness is NOT a benefit to the organism," and "reproduction is actually an expense to life. There are even some animals which die immediately after reproducing. This cannot be a benefit to the individual."
     
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  3. John Connellan Valued Senior Member

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    BigBlue and Paul Samule: look I want to get to the heart of the matter because u are not looking at what i am really trying to say. I DO understand reproduction, fitness and their relationship benefit from both our points of view but I don't actually think the accepted one is the right one. This is probably terribly arrogant of me because I don't consider myself a 'great' biological scientist who could overturn existing theories. Thats why I would rather u help me now instead of arguing.

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    This is my point of view:

    Individuals live merely to pass on their genes. Genes are really what life is about because they store the information that codes for life and THEY are the replicating components. Everything else on our body is merely a tool shaped by the evolution of these genes down the years in order to cope with changing environments. A species will only last if it can help its genes replicate in a certain environment. If not, the genes will ensure that a different species involves. This is the basis of why species are really not that important in life.

    I also believe that 99% of our behaviour stems from genetic "urges" and that almost everything we do can be explained as a benefit to our genes. Our genes have been apparently quite "clever" over the years however. We have always thought of ourselves as individuals with our own goals and for various reasons we enjoyed reproduction and even the sight of little children in our homes. We never knew (for a long time) why we had these urges.
    Then along came genetics and the realisation that we are not just individuals but we are carriers of our genes which had their own agenda; mainly to reproduce and thrive in the environment.

    Now, to me, an altuistic act should be defined as one which does not benefit the giver as an individual but might still benefit his genes. HOWEVER, his genes are not him are they (if u look at it in an individualistic sense)? Genes have long been said to be selfish and so there are very few if any "TRUE" altruistic acts. Biologists, as u say, have now come to define altruism as that which benefits the genes and not the individual as I see it. This is where I have my problem.

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  5. paulsamuel Registered Senior Member

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    There is so much misunderstanding in this post, it's hard to know where to begin.
    I don't necessarily agree with that, especially in the case of humans, but this is independent of the question. Try to keep your questions uncluttered with other topics which can lead to confusion.

    This is not true. The individuals in a population replicate through reproduction.
    Genes are not organisms, are not individuals in a population, are not the units upon which selection acts.

    Again, this is not true. Do not confuse a group like species with an individual. Genes, ensure nothing.
    What do you mean that species aren't important in life? That's a statement with no meaning.

    behaviours evolve to aid in propagation. nothing more nor less.

    Please try to stick to science. Genes are not clever.

    We are undoubtedly a product of our environment and our genetic background. That is life. You have not, and could not, have a say in your composition. Get over it, and try to make the best of what control you do have in your life.

    Why do you insist on referring to genes as people? They are not. Your genes are YOU! What benefits you, benefits your genes, and vica versa. Altruism has been explained and discussed in this thread. You, yourself, gave a definition of altruism! Go back and read it. It has nothing to do with genes.

    You also appear to be referring to, and misinterpreting i might add, Dawkins. Dawkins does not think genes are individuals. He uses it as an analogy. You might want to read, or re-read, his works.

    No, one's genes are oneself.

    This is a very confused statement where the second half of the sentence has nothing to do with the first half. Let's dissect it; the first half is incorrect because it was only since the misinterpretation of Dawkins book was possible in the mid-1970's that the concept of selfish genes existed.
    The second half of the sentence, "and so there are very few if any "TRUE" altruistic act," has nothing to do with how long genes were said to be selfish. There are no altruistic acts, simply because altruistic traits cannot evolve in a population without some benefit to the donor of altruism.

    then you see it wrong. the definition of altruism has remained the same. Try re-reading this statment by me,

    "how can altruistic traits evolve in a population? How can a trait that sacrifices one's fitness to increase the fitness of another, evolve? Answer; if the benefit to the sacrificer's fitness is greater than the fitness cost of the sacrifice. This is the only way!


    individuals are the units of selection, not genes. genes are components of an individual, but it is the individual, a composite of all one's traits, that is the unit of selection.
     
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  7. John Connellan Valued Senior Member

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  8. BigBlueHead Great Tealnoggin! Registered Senior Member

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    Whether or not the genes are the individual is not important to this discussion; emergent properties of human beings, like an inherited social order, are obviously not coded for in the human genome in the form that we have them.

    The point is that selection almost always happens at the level of the individual - I only recall one case where this is not true, which is the example of gamete weighting.

    But a few posts ago, you said that reproduction had no benefit.

    That is not the essence of evolution; evolution acts upon the individual. An organism can have a very large number of deleterious alleles that reduce its fitness, but as long as it has other alleles that make up the difference it can still survive to reproduce.
     
  9. John Connellan Valued Senior Member

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    I think its the ONLY worthy discussion here because I understand the topics u speak of but I just don't agree that altruism should have genetic conotations in ecology or even evolutionary biology. I think it should be a word describing behaviour which decreases the individuals ability to have energy and reproduce (even though it still increases the overall fitness of the organism through genetics).

    This is where u are not understanding me. I said it has no benefits to the individuals doing the reproducing.

    No, it acts directly upon the individual. It also acts indirectly through this method on the gene pool.
     
  10. BigBlueHead Great Tealnoggin! Registered Senior Member

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    I don't think that the word "pear" should be used to describe the swollen ovary of the organism Pyrus communis, but I also don't imagine that anyone else wants to change their definition just for me...

    Then who benefits? You've already stated that being born is not a benefit, so since neither the individual nor the offspring benefit, it would seem you've eliminated any point.

    Before you say that it benefits the GENE, which is idiotic, let me say this. If I replaced "the gene" with some other body part, like "the arm" or "the epithelial cell", this statement would make no sense. Your legs don't carry you around because they "derive benefit from having you on top of them".

    The organism is a whole; its genome is a whole. When you reproduce, you pass on whichever half of your genetic code (ignoring crossing over for the moment, because I don't understand that too well) to your children. Sexual reproduction is a widespread mechanism, but it's not the only one.

    Genetic interchange in bacteria is totally seperate from reproduction, for instance. Bacterial conjugation results in the interchange of genetic material; bacterial reproduction produces clones of the parent bacterium. Evolutionarily speaking, the bacteria have a much better system than we do; a successful trait can spread through their population within a generation, instead of between as with sexual reproduction.
     
  11. John Connellan Valued Senior Member

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    Well its also because Im sure it is used by many other people too and I was taught that definition myself if I can remember correctly. If u and Paul are claiming that it is the "official" definition then I am willing to accept it however as i am sure u 2 have read a lot more evolution books than I have.

    Why are u asking this question? U know what I'm going to answer......

    That is not idiotic.

    The genes that code for the leg DO actually derive benefit from having u on top. Its like a symbiotic relationship. How could a leg survive without the top?

    Yes, when u reproduce there is a 50% chance that a certain gene will survive into the next generation and an even higher chance if u have more children. I know it is not accurate but an analogous way of looking at it is to say that "goal" of genes is to survive indefinitely using individuals as carriers but I believe because nobody wants to die, that the goal of individuals is different.

    Exactly. Why are they more successful? Because the genes have can spread quicker which has nothing to do with how sophisticated the bacteria is as an individual organism.
     
  12. BigBlueHead Great Tealnoggin! Registered Senior Member

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    Look genius, you've been arguing that organisms always reproduce at cost to themselves because this promotes the transmission of their genetic material.

    I gave you an example of an organism which transmits its genetic material without needing to reproduce. Why in hell would they reproduce then? Reproduction has material costs for the bacterium just as it does for us; it would be easier for a bacterium to involve itself in a social group and just play genetic interchange all day - yet no bacteria do this. They uniformly reproduce themselves in vast quantities until they go dormant for lack of resources - even though there is no genetic transmission in doing so. They won't get any genetic bonuses for interchanging their genetic material with their own offspring because they already have it. So, what's the point?

    Why does the most widespread set of organisms in the world bother to reproduce?
     
  13. Buckaroo Banzai Mentat Registered Senior Member

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    Note to spuriousmonkey: at any moment it touches what was intended to be the topic. So you do not to have the work of reading it all to then be disapointed.

    Was not directed for me, but since I'm agreeing with John Connellan (in fact, I'm agreeing with both "sides", because no one is saying that different things happens, what is differing is not even the interpretation of the occurrence, but just the description/definition...). First, because they probably inherited this property to begin with; and second, because any being that somewhen inherited the trait of being infertile didn't passed its genes to anyone else (or did horizontally) and eventually died, while others that did reproduce, still had their descendants.

    The second part of your post is more or less answered by it. Any bacteria that didn't "bothered" to reproduce, eventually had became extinct, if such thing could even start to evolve once, which I seriously doubt.

    This things of units of selection is a quite messy, and I think that everybody is right, there wouldn't be different things occurring if we say that the "real" unit of selection are the genes than if we said that is the individual or the population. Some time ago I've read a article about it (but I do not remember that much) where I saw that some people say that genes are the selection units and individuals are the interface. Let's supose that finches had their beaks shrinked in some segment of their evolution? What was selected? If we look at the level of the individual, individuals that had smaller beaks; if we look at the level of genes, any genes which determine the smaller beak plus all the genes that make the rest of the bird; and with this thing of interface view, the genes that produce the bird with small beak through the individuals that possessed this phenotype. Three forms (and I do not doubt that there are more) to express exactly the same thing.

    About selfish/altruist behavior, and benefits, I personally prefer the point of view that that the behavior that survives (and consequently the genes that determine this behavior and not necessarily the individuals that are actually having this behavior) is the one which results in a optimal production of offspring in relation with the environment. Eventually it may looks like that there are individuals that help other(s) at their own sacrifice (eventually, leading to his death, in some cases), like if their were gentle or even brave when it comes to save his fellows. The sacrified individual do not have any benefit dying, the benefited were related individuals saved due to his sacrifice. At the individual level, it was altruist, the individual did not gain anything. It only occurred because despite of the selection against of this individual, there still are many other individuals that have these genes determinant of a dispositon to sacrifice saving others with "presumably" the same genes; while in a hypotethic population without this behavior/genes, each one them would try to save himself leding to the death of them all, or most of them. A example of this behavior is some sort of aphids against some sort of wasp that goes laying one egg in each individual, and all the aphids do is to release some sort of glue from them, that keeps the wasp stuck on them, killing both the savior and the wasp.

    Other thing that were mentioned at some point, but I didn't adress yet, was the about reproduction being a benefit for the progenitors, and therefore, happening because of it. If wasn't that what was meant, I'm sorry, is that the impression that I have. I have the most mechanist point of view as possible, so I think that living beings reproduce just because they do; that's what define living beings. Eventually evolution favoured the ones which had a offspring that bring them benefits - probably at the same time making them capable of having even more offspring later.
    Just think about the first reproducing entity; it did not wait for the certain conditions in which by making a relatively equal copy of itself would bring any sort of benefit; because it was not capable of intentionally wait for anything anticipated, and the reproduction isn't beneficiary at any moment that is possible to occur; and I really doubt that it was purposefully designed to reproduce only under the ideal conditions in which the reproduction would be a benefit. It may had caused progenitor death at the very following moment, but if it did could reproduce, it would probably do exactly the same soon, until a mechanism that results in reproduction under certain conditions had evolved.


    Wow, I've written a lot, I hope my language errors do not cause any serious injuries.
     
  14. paulsamuel Registered Senior Member

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    882
    I don't really want to continue this discussion, but I feel compelled if only to point out the errors and mistakes to others who may be reading this thread. So,
    "Once more unto the breach, dear friends, once more;
    Or close the wall up with our English dead!
    In peace there's nothing so becomes a man
    As modest stillness and humility;
    But when the blast of war blows in our ears,
    Then imitate the action of the tiger;
    Stiffen the sinews, summon up the blood,
    Disguise fair nature with hard-favor'd rage;
    Then lend the eye a terrible aspect."

    -Henry V by Wm. Shakespeare

    This is a ridiculous statement. Individuals reproduce and reproduction is a multi-genic evolved trait which allows genetic representation of an individual in subsequent generations. It misleads the reader into thinking that an individual's genes are somehow manipulating the individual into reproducing. An individual's genes are components of that individual, not parasites involved in competition or predation upon an individual.

    No! That's not the case. Genes DO NOT code for an individual. Genes code for proteins and protein products, RNA, etc. NOT an individual! Selection acts upon the individual, components of which are genes. I understand completely what you're saying, what I'm wondering is if you do.

    Absolutely not! Genes cannot ensure, nor can they allow a species to exist or not. Genes are not the unit of selection and neither are species!

    Here again the statement misleads the reader by implying that the propagation of genetic representation of an individual, of which genes are a component, is a benefit to the genetic material itself at the expense of the individual.

    I believe I quoted you correctly. If you mean something other than what you've written, then you should warn us.

    I do stick to science.
    You appear to be bitter about what you think is a manipulation of yourself by your genes.

    Genes are components, nothing more. You are attempting to give genes properties which they do not posess.

    May I also point you to S.J. Gould, The Structure of Evolutionary Theory, the section entitled The Evolutionary Definition of Selective Agency and the Fallacy of the Selfish Gene, pp. 613-644.

    Well, genes don't have goals, they are merely components of an individual, but in spirit, that's what I'm saying.

    So you meant to say that selection is responsible for the apparent selfishness in genes and for the lack of true altruism? If that's the case, I can't see why you think selection can account for apparent selfishness in genes.

    I did not say that. I said that there is one definition for altruism, biologists did not change it. My contention with you was that you stated that altruism existed in biology and gave the example of breastfeeding. Breastfeeding is an obvious example of mutual benefit, so it's not altruism. My disagreement with you grew as I read you saying things like,
    AND
    AND
    i just realized that we may have argued before on this topic. you are that Dennett proponent with whom i argued almost a year ago, are you not? if you are, you realize Dennett is not a biologist, don't you?

    well, i'll continue tomorow after a good nights rest.
     
  15. paulsamuel Registered Senior Member

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    you mean selection acts on the individual

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    .

    Populations evolve.
     
  16. paulsamuel Registered Senior Member

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    Biologists needed to explain apparent altruisitc acts observed in the wild, they have done that with the four conditions I posted a while ago. This is the importance of altruism in behavioural ecology and evolution. That you don't like it, is independent of its importance.

    Individuals are selected (the unit of selection) and populations evolve.
     
  17. paulsamuel Registered Senior Member

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    Please, don't do that. You know what he means. Components of an individual do not evolve separately. This is a good point.

    You're right, they're not accurate and should not be used. They lead to confusion and misunderstanding. We should stick to talking about evolved traits and what that means for individuals and the genes with which they are composed. A trait is maintained in a population over time if the trait is heritable and if the individuals with that trait are successful reproducers. Individuals with traits that forgo reproduction for prolonged life will not be maintained in the population. They will die off, go extinct, and be replaced by the reproducers. In fact, traits like this cannot evolve because they would be eliminated so quickly from populations.
     
  18. paulsamuel Registered Senior Member

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    begs the question, i.e. merely postpones the need for the explanation.

    nor could it have inherited them. the example is not possible.

    he's talking about sexual reproduction, bacteria can still reproduce without the costs that John has been bringing up.

    The individual is selected. The individual is the unit that interacts with the environment and the unit that dies if it is selected against. The genes are selected only as they are components of the individual.

    You misunderstand the discussion. Let me repeat:
    "how can altruistic traits evolve in a population? How can a trait that sacrifices one's fitness to increase the fitness of another, evolve? Answer; if the benefit to the sacrificer's fitness is greater than the fitness cost of the sacrifice. This is the only way! So, there are no sacrifice genes or altruistic genes because they could not evolve except under the one of the four conditions which I listed in a previous post.

    reproduction is an evolved trait as you stated in the first paragraph of your post in response to BigBluHead. reproduction only occurs becasue it increases fitness in the individuals who reproduce.
     
  19. Buckaroo Banzai Mentat Registered Senior Member

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    Of course it could, for example, if it's a recessive trait, or, what I've meant in this specific case, in horizontal transmission. Althought I don't know how is the level of expression of horizontally acquired genes, maybe they just are expressed in the next generation's phenotype, when we're not talking about viruses. Anyway, the next generation would had inherited infertility.


    I was referring to a example of non-sexual reproduction. John Connellan had said that the "goal" of living beings is genes transmission (not in this words), so then BigBlueHead asked why bacteria just do not stop reproducing (since it's was affirmed as a cost by Connellan) and only do horizontal transmission. At least was what I understood.


    Okay, they're selected indirectly, but still are selected. I still see this thing of units of selection as same forms to say the same thing, as passive or active voice sentences; the occurrence stills the same, but eventually one way is better to understand some certains details of what happened.

    ...I think that what I said is according to this, but only I expressed (very bad, I admit) in advantage to genes rather than to individual fitness, what I think that gives a better view of the evolutionary advantage of this suicide, because if we consider fitness as the ability of the individual to produce offpring, then there's no benefit to the suicide individual, since it's dead, its fitness downs to zero. Escaping, it maintains its fitness.
    But if we define fitness as the capacity of the individual to propagate its own genes (which is hidden in the earlier definition), we can see clearlier that despite of the individual impossibility to produce more offpring, the suicide means more fitness, since even only two individuals of the suicidal's offpring already have a greater potential to propagate its [much of the same (if not all, in parthenogenic species)] genes than the one non-suicidal alone.
    So the "fitness of another" stills being one's "extended" fitness, or the gene's fitness (what would be defined as the capacity of propagate itself through individuals, or the gene capacity of being as long-lived as possible, etc).
     
    Last edited: May 23, 2004
  20. paulsamuel Registered Senior Member

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    then it could pass those traits on. you can't argue both sides of the question, makes you look like your disagreeing just to be disagreeable.

    well, perhaps we both misunderstood. from what i understand, john's point is that it's the goal of the genes to be transmitted and that genes manipulate individuals to reproduce to meet these goals at the cost of the individual. so, since bacteria don't need to reproduce to transmit genes, BBH asks why do they reproduce? The implication being that genes don't need to manipulate bacteria for transmission, therefore bacteria reproducing would be merely a cost to them, therefore wouldn't do it. Since we know they do, this is evidence that John's view is wrong.

    of course they are, since they are components of the individual, no one said they weren't. John's point is that genes are the unit of selection and individuals, mere carriers (the extension of the phenotype).

    It's not the same thing at all. Even the genic selectionists who developed the concept have abandoned it. Just a few crackpots left, like Dennett.

    it wouldn't make sense at the level of gene selection because the individual and the gene are on different evolutionary trajectories, i.e., whats good for the gene is detrimental to the individual according to John. That's what I'm arguing against.

    it appears to me that you don't understand the difference between selection at the individual level vs. selection at the gene level, and the implications those differences have in evolutionary biology, although I am having trouble understanding your posts, so maybe it's me.
     
  21. John Connellan Valued Senior Member

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    Well I disagree with u here. I wouldn't go as far as saying they are true parasites (and its connotations

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    ) but I believe that genes do appear to manipulate us in almost everything we do. Of course I say "appear" because genes are not organisms but through the process of NS it appears like this.

    The individual is nothing but a collection of those preteins. Without genes u would have no individual so I'm right

    They can't ensure but a varied genepool allows species to adapt to changing environments and thus exist.

    In the case of reproduction and breast feeding etc. then yes, the propogation comes as a cost to the individual. there is no misleading. this is what happens!

    Quote marks mean do not take it literally.

    I am dissapointed that u cannot see the points I am arguing as true. Especially since this is your field of knowledge right?

    Like what?

    Selection makes it appear like individuals are being, as u say, manipulated by genes (almost as if the genes were like living parasites). Because of this fact, many things in nature when seen in this (quite modern) light make it appear as though genes are selfish.

    There is no benefit to the breast feeder!!! Simple as that. The breast feeder GIVES milk and so spends resources on a different individual which is the offspring. Only the genes benefit EVEN though individuals themselves are directly selected for.

    Definitely not no

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  22. John Connellan Valued Senior Member

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    Again I meant "goal" as an analogy with individuals. Of course genes cannot have goals. Selection makes it appear they have goals but in fact they are just passive components of an active process.

    Well hold on, why DO bacteria reproduce if they don't have to? Answer this and I will respond with my answer.

    Only u ever used the word "unit". I said genes can be selected for indirectly through their carrier (as genes cannot exist on their own

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    Dear Lord u haven't got a clue what I'm saying. I would imagine about 90% of acts that are good for the gene (all acts!) are actually beneficial to the individual. Its really only when the individual gets to the reproducing stage that the "selfishness" of the genes becomes apparent.
     
  23. Buckaroo Banzai Mentat Registered Senior Member

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    ...arguing both sides? You meant, being contradictory and saying that at the same time something could and couldn't happen? That's not what I've, said, I said that although is possible to transmit infertility, this is never in advantage in relation to fertility, so it would never "win" (at least not not extraordinary situations, I think), and if it did, would became extinct as soon as the infertile generation dies.


    I don't see much difference in what you and me undertand from that... anyway, I don't think that worth keep talking of this detail, since I don't agree that genes "goal" are to be merely transmitted, but to be reproduced, and then keep "living". I'd not even say that's a goal.

    Is about that that is the Dawkin's book "the extended phenotype"? I thought that was something about the phenotype of culture, but now it makes more sense for a biology book. I also didn't realized what was "the river out of eden" until I read about the book. Surprisingly I've made a similar analogy, with exception of the Eden part once, before knowing it

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    . But I didn't thought that was a analogy strong enough to write a whole book...

    Wow, I've thought that was just the opposite....

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    ...but I agree (with this different evolutionary trajectories), unless the good for the individual means to pass his own genes, not merely reproducing or surviving, which is what come to my mind first when we're differentiating genes from the individual... in this same example of the suicidal aphids, I can't see how dying could be good for the individual in anyway, only if we state that the individual wants to its living offspring survive, but I don't like to put this sort of thoughts in the heads of tiny aphids...


    It's really probably it's me... as I've said in the right above, I think that since the "goal" of individuals is to pass it's genes to the next generation, and not merely reproduce, it's pretty much the same thing. The "real" selection, of course, is allways happening at the level of the individual, the gene level is to me like a "zoom in" to what's the consequences in the gene level...

    The things I've read about that untill now were enough to me understand almost all the behaviors I've known, more specifically this ones, be "truly" or apparently altruistic... I'm going to check some cited texts and books. I've read only Dawkin's "climbing mount improbable", "blind watchmaker" and "selfish gene". From Gould, who seems to oppose the point of view of selfish gene, I've read only "Full house", that didn't dealed with this point I think.
     

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