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Fwd: PNAS paper on multiple origins of compound eyes Comments?

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  • Phil Skell
    ... [Non-text portions of this message have been removed]
    Message 1 of 5 , Feb 1, 2002
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      >http://www.pnas.org/cgi/content/abstract/032483599v1
      >
      >Molecular phylogenetic evidence for the independent evolutionary origin of
      >an arthropod compound eye
      >
      >Todd H. Oakley and Clifford W. Cunningham
      >Department of Biology, Duke University, Box 90325, Durham, NC 27708-0325
      >
      >Edited by James W. Valentine, University of California, Berkeley, CA, and
      >approved November 30, 2001 (received for review September 12, 2001)
      >
      >Eyes often take a central role in discussions of evolution, with debate
      >focused on how often such complex organs might have evolved. One such debate
      >is whether arthropod compound eyes are the product of single or multiple
      >origins. Here we use molecular phylogeny to address this long-standing
      >debate and find results favoring the multiple-origins hypothesis. Our
      >analyses of DNA sequences encoding rRNA unequivocally indicate that
      >myodocopidsthe only Ostracoda (Crustacea) with compound eyesare nested
      >phylogenetically within several groups that lack compound eyes. With our
      >well-supported phylogeny, standard maximum likelihood (ML) character
      >reconstruction methods significantly reconstruct ancestral ostracods as
      >lacking compound eyes. We also introduce a likelihood sensitivity analysis,
      >and show that the single-origin hypothesis is not significantly favored
      >unless we assume a highly asymmetric model of evolution (one favoring eye
      >loss more than 30:1 over gain). These results illustrate exactly why
      >arthropod compound eye evolution has remained controversial, because one of
      >two seemingly very unlikely evolutionary histories must be true. Either
      >compound eyes with detailed similarities evolved multiple times in different
      >arthropod groups or compound eyes have been lost in a seemingly inordinate
      >number of arthropod lineages.
      >
      >
      >To whom reprint requests should be addressed at present address: Department
      >of Ecology and Evolution, University of Chicago, 1101 East 57th Street,
      >Chicago, IL 60637. E-mail: tho@....
      >
      >www.pnas.org/cgi/doi/10.1073/pnas.032483599


      [Non-text portions of this message have been removed]
    • Cliff Lundberg
      ... One has to pay to see the full text of the article, so I guess I ll never know the details of the likelihood-sensitivity analysis that is referred to,
      Message 2 of 5 , Feb 2, 2002
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        Phil Skell wrote:
        > >http://www.pnas.org/cgi/content/abstract/032483599v1
        > >Molecular phylogenetic evidence for the independent evolutionary origin of
        > >an arthropod compound eye
        > >Todd H. Oakley and Clifford W. Cunningham
        > >Department of Biology, Duke University, Box 90325, Durham, NC 27708-0325

        > >Eyes often take a central role in discussions of evolution, with debate
        > >focused on how often such complex organs might have evolved. One such debate
        > >is whether arthropod compound eyes are the product of single or multiple
        > >origins. Here we use molecular phylogeny to address this long-standing
        > >debate and find results favoring the multiple-origins hypothesis. Our
        > >analyses of DNA sequences encoding rRNA unequivocally indicate that
        > >myodocopidsthe only Ostracoda (Crustacea) with compound eyesare nested
        > >phylogenetically within several groups that lack compound eyes. With our
        > >well-supported phylogeny, standard maximum likelihood (ML) character
        > >reconstruction methods significantly reconstruct ancestral ostracods as
        > >lacking compound eyes. We also introduce a likelihood sensitivity analysis,
        > >and show that the single-origin hypothesis is not significantly favored
        > >unless we assume a highly asymmetric model of evolution (one favoring eye
        > >loss more than 30:1 over gain). These results illustrate exactly why
        > >arthropod compound eye evolution has remained controversial, because one of
        > >two seemingly very unlikely evolutionary histories must be true. Either
        > >compound eyes with detailed similarities evolved multiple times in different
        > >arthropod groups or compound eyes have been lost in a seemingly inordinate
        > >number of arthropod lineages.

        One has to pay to see the full text of the article, so I guess I'll never know
        the details of the "likelihood-sensitivity analysis" that is referred to,
        which is
        apparently based on the inane assumption that a mutation causing eye loss
        is no more likely than a mutation that creates eye "gain". If I were estimating
        the relative likelihood of a mutation creating a useful new complex structure
        vs a mutation causing loss of a structure, on mechanical grounds alone I
        would have to set the factor at far more than 30. The evident trend toward
        reduction in general should obviously be a further consideration weighing
        against the equal likelihood of elaboration vs reduction.

        This is an example of people attempting to do worthwhile science, but being
        led astray by a bad general concept, in this case the Dawkinsian notion that
        elaborative mutations are no problem at all, they're just more mutations, like
        mutations for brown eye-color or whatever. And of course here there is
        prejudice
        against complex beginnings followed by paths of reduction; this doesn't fit
        the
        happy progressive model of evolution scientific institutions seem bound to
        support.

        What is Phil's comment on this?

        Cliff
      • Phil Skell
        Phil does not know enough of this domain to make a worthwhile comment. Let me know if you would like a full copy of the article for evaluation. ... [Non-text
        Message 3 of 5 , Feb 2, 2002
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          Phil does not know enough of this domain to make a worthwhile comment.

          Let me know if you would like a full copy of the article for evaluation.


          At 01:10 AM 02/02/2002 -0800, you wrote:
          >Phil Skell wrote:
          > > ><http://www.pnas.org/cgi/content/abstract/032483599v1>http://www.pnas.o
          > rg/cgi/content/abstract/032483599v1
          > > >Molecular phylogenetic evidence for the independent evolutionary origin of
          > > >an arthropod compound eye
          > > >Todd H. Oakley and Clifford W. Cunningham
          > > >Department of Biology, Duke University, Box 90325, Durham, NC 27708-0325
          >
          > > >Eyes often take a central role in discussions of evolution, with debate
          > > >focused on how often such complex organs might have evolved. One such
          > debate
          > > >is whether arthropod compound eyes are the product of single or multiple
          > > >origins. Here we use molecular phylogeny to address this long-standing
          > > >debate and find results favoring the multiple-origins hypothesis. Our
          > > >analyses of DNA sequences encoding rRNA unequivocally indicate that
          > > >myodocopidsthe only Ostracoda (Crustacea) with compound eyesare nested
          > > >phylogenetically within several groups that lack compound eyes. With our
          > > >well-supported phylogeny, standard maximum likelihood (ML) character
          > > >reconstruction methods significantly reconstruct ancestral ostracods as
          > > >lacking compound eyes. We also introduce a likelihood sensitivity
          > analysis,
          > > >and show that the single-origin hypothesis is not significantly favored
          > > >unless we assume a highly asymmetric model of evolution (one favoring eye
          > > >loss more than 30:1 over gain). These results illustrate exactly why
          > > >arthropod compound eye evolution has remained controversial, because
          > one of
          > > >two seemingly very unlikely evolutionary histories must be true. Either
          > > >compound eyes with detailed similarities evolved multiple times in
          > different
          > > >arthropod groups or compound eyes have been lost in a seemingly inordinate
          > > >number of arthropod lineages.
          >
          >One has to pay to see the full text of the article, so I guess I'll never know
          >the details of the "likelihood-sensitivity analysis" that is referred to,
          >which is
          >apparently based on the inane assumption that a mutation causing eye loss
          >is no more likely than a mutation that creates eye "gain". If I were
          >estimating
          >the relative likelihood of a mutation creating a useful new complex structure
          >vs a mutation causing loss of a structure, on mechanical grounds alone I
          >would have to set the factor at far more than 30. The evident trend toward
          >reduction in general should obviously be a further consideration weighing
          >against the equal likelihood of elaboration vs reduction.
          >
          >This is an example of people attempting to do worthwhile science, but being
          >led astray by a bad general concept, in this case the Dawkinsian notion that
          >elaborative mutations are no problem at all, they're just more mutations, like
          >mutations for brown eye-color or whatever. And of course here there is
          >prejudice
          >against complex beginnings followed by paths of reduction; this doesn't fit
          >the
          >happy progressive model of evolution scientific institutions seem bound to
          >support.
          >
          >What is Phil's comment on this?
          >
          >Cliff
          >
          >
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          [Non-text portions of this message have been removed]
        • Cliff Lundberg
          ... I just wondered why you thought it of particular interest in the first place, why you were interested in our comments. How much does one have to know to
          Message 4 of 5 , Feb 2, 2002
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            Phil Skell wrote:
            >Phil does not know enough of this domain to make a worthwhile comment.

            I just wondered why you thought it of particular interest in the first place,
            why you were interested in our comments.

            How much does one have to know to opine that an elaborative mutation
            forming a complex structure in the right place is less likely than a mutation
            which is destructive, which simply stalls the development of a feature?

            Cliff
          • Phil Skell
            The closing sentences of the abstract seemed clear enough until you cast your skepticism on it. Phil ... [Non-text portions of this message have been removed]
            Message 5 of 5 , Feb 2, 2002
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              The closing sentences of the abstract seemed clear enough until you cast
              your skepticism on it. Phil


              At 11:55 AM 02/02/2002 -0800, you wrote:
              >Phil Skell wrote:
              > >Phil does not know enough of this domain to make a worthwhile comment.
              >
              >I just wondered why you thought it of particular interest in the first place,
              >why you were interested in our comments.
              >
              >How much does one have to know to opine that an elaborative mutation
              >forming a complex structure in the right place is less likely than a mutation
              >which is destructive, which simply stalls the development of a feature?
              >
              >Cliff
              >
              >
              >Yahoo! Groups Sponsor
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              >72d728f.jpg
              >
              >To unsubscribe from this group, send an email to:
              >CreationEvolutionDesign-unsubscribe@yahoogroups.com
              >
              >
              >
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              ><http://docs.yahoo.com/info/terms/>Yahoo! Terms of Service.


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