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Thread: Natural Selection and Linkage Disequilibrium

  1. #1 Natural Selection and Linkage Disequilibrium 
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    It seems that someone has beaten me to it.

    Dr Josep Comeron of the University of Iowa is
    simulating the effect of positive and negative
    selection at 1 MILLION nucleotide sites for all
    loci throughout the genome of the species
    drosophila (fruit fly).

    A critical problem to the theory of natural selection
    is that of Genetic Linkage.

    http://www.pubmedcentral.nih.gov/art...?artid=1851075

    http://www.genetics.org/cgi/content/abstract/140/2/821

    Even transient instances of linkage between beneficial
    and deleterious alleles in the genetic background
    can seriously weaken the effect of natural selection
    as Comeron explains in his last publication

    http://www.nature.com/hdy/journal/v1.../6801059a.html

    So Comeron is now leading in the field in understanding what
    the real effect of selection is across the genome as opposed to
    at isolated parts of it, which has been the case up until now.

    Hopefully, even die hard Darwinists will have to come to
    terms with the theoretical and experimental results which
    show that natural selection is a very minor player in
    evolutionary change.


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  3. #2  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    I guess you didn't actually read the article.

    Shame you also posted your novel insights a month after the article was out.


    some conclusions from the article:
    Our results suggest the possibility of a novel complement to existing explanations for why truly asexual populations are evolutionarily short-lived: Either an asexual population does not adapt and goes extinct as a result of the slow accumulation of deleterious mutations, as suggested by existing theory (18, 19, 36), or else it adapts and goes extinct as a result of the mutation-rate catastrophe.
    You might have noticed the stress on asexual reproduction if you had actually read the article. I'm not sure the article isn't total bullshit since we do actually have ancient pure asexual species still currently living.

    Moreover:
    To the extent that conditions for the mutation rate catastrophe are met in real populations, then, its occurrence would greatly broaden the circumstances under which asexual populations will ultimately be less successful than sexual populations.
    Once again the conclusion. Asexual reproduction is susceptible to the effect of mutation rate catastrophe.

    And some speculation:
    It is tempting to speculate that the mutation rate catastrophe phenomenon that we have observed here played a role in the early establishment of recombination in the most primitive life forms (41). It seems probable that adaptation was continual in primordial populations and that only rudimentary mechanisms of genomic proofreading and repair had evolved, such that mutation rates were closer to intolerable values than they are in most present forms. Under these circumstances, the mutation-rate catastrophe could have posed an imminent threat to any purely asexual population.
    Once again, the stress on dangers for purely asexual populations. And a inference for the dangers that it might have posed during the first stages of life.


    Note now how nothing implies it poses a problem for the theory of evolution. Of course you didn't manage to catch that message, since you never read the paper.


    "Kill them all and let God sort them out."

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  4. #3  
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    You might have noticed the stress on asexual reproduction if you had actually read the article. I'm not sure the article isn't total bullshit since we do actually have ancient pure asexual species still currently living.
    The point the researchers are making is that selection is a very poor candidate for the evolution of asexual species because of genetic linkage.

    Once again the conclusion. Asexual reproduction is susceptible to the effect of mutation rate catastrophe.
    Yes, if selection is the mechanism.

    Once again, the stress on dangers for purely asexual populations. And a inference for the dangers that it might have posed during the first stages of life.
    Depends on whether genetic recombination can break down tight linkage between loci that are very close to each other on the chromosome. The evidence shows that it can't. Recombination for sexual and Gene transfer for asexual organisms, does,however, prevent the worst cases of linkage.

    Note now how nothing implies it poses a problem for the theory of evolution. Of course you didn't manage to catch that message, since you never read the paper
    Try reading the second paper which describes actual observations of natural selection on drosophila and the third which talks about the problem of the genetic background which recombination can't help with.
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  5. #4  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    sure, if you read the first one.
    "Kill them all and let God sort them out."

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  6. #5  
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    Quote Originally Posted by spuriousmonkey
    sure, if you read the first one.
    I have read it. It outlines a problem...that of genetic linkage.
    The author is really making the case for sex and recombination
    above all else.

    It doesn't invalidate evolution by natural selection, but it
    indicates what could happen in the worst cases....the problem
    is related to that of "Muller's Ratchet" whereby selection can
    lead to the accumulation of deleterious genes and tip a
    population into mutational meltdown.

    The second paper is an attempt to describe what has been
    observed occuring in drosophila and why selection has been
    so ineffective.
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