Dawkins on Kimura

Discussion in 'Health and medical' started by Tim Tyler, Feb 22, 2004.

  1. Tim Tyler

    Tim Tyler Guest

    Another quotable bit:

    ``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable (I
    would argue) that most if not all the evolutionary changes we actually see in the macroscopic world
    (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A Devil's
    Chaplain, p.85.

    I'm not sure about the "all" but I'm inclined to agree with the "most".

    Drift may have something to say about small populations on islands around speciation events - but
    it's probably a bit player in most other places - as far as the *features* of organisms go (as
    opposed to the makeup of their genes).
    --
    __________
    |im |yler http://timtyler.org/ [email protected] Remove lock to reply.
     
    Tags:


  2. Guy Hoelzer

    Guy Hoelzer Guest

    in article [email protected], Tim Tyler at [email protected]
    wrote on 2/22/04 10:56 PM:

    > Another quotable bit:
    >
    > ``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable (I
    > would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    > world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    > Devil's Chaplain, p.85.

    IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
    "evolution" in complex dynamical systems that seemingly lack the basic ingredients for the process
    of natural selection (e.g., populations of reproducing agents), they will look increasingly like closed-
    minded zealots as time goes on. At this point, I think it is absurd and telling that Dawkins begins
    his argument with such a false premise as "Darwinian selection remains the only explanation for
    adaptive evolution."

    > I'm not sure about the "all" but I'm inclined to agree with the "most".
    >
    > Drift may have something to say about small populations on islands around speciation events - but
    > it's probably a bit player in most other places - as far as the *features* of organisms go (as
    > opposed to the makeup of their genes).

    Is this all just a gut feeling on your part? That would be fine. I just want to know if there is any
    reason your assertion should be persuasive to others.

    Cheers,

    Guy
     
  3. Dkomo

    Dkomo Guest

    Tim Tyler wrote:
    >
    > Another quotable bit:
    >
    > ``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable (I
    > would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    > world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    > Devil's Chaplain, p.85.
    >
    > I'm not sure about the "all" but I'm inclined to agree with the "most".
    >
    > Drift may have something to say about small populations on islands around speciation events - but
    > it's probably a bit player in most other places - as far as the *features* of organisms go (as
    > opposed to the makeup of their genes).

    Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
    skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
    old age, have different reactions to medications, have different physical abilities like being able
    to run for long distances, sing very well, be really strong, and so on and so on -- these are all
    the result of adaptations and natural selection?

    Wow.

    [email protected]
     
  4. Tim Tyler

    Tim Tyler Guest

    Guy Hoelzer <[email protected]> wrote or quoted:
    > in article [email protected], Tim Tyler at [email protected]

    > > Another quotable bit:
    > >
    > > ``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
    > > (I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    > > world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    > > Devil's Chaplain, p.85.
    >
    > IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
    > "evolution" in complex dynamical systems that seemingly lack the basic ingredients for the process
    > of natural selection (e.g., populations of reproducing agents), they will look increasingly like
    > closed-minded zealots as time goes on. At this point, I think it is absurd and telling that
    > Dawkins begins his argument with such a false premise as "Darwinian selection remains the only
    > explanation for adaptive evolution."

    I can't really make out what you are on about here.

    It seems as though you are asserting that "populations of reproducing agents" "lack the basic
    ingredients for the process of natural selection".

    That doesn't seem to make much sense.

    Or maybe you are saying that evolution (of a sort) can occur in some systems which "lack the basic
    ingredients for the process of natural selection". I guess that is true in theory - e.g. if you have
    a hypothetical system - where agents all reproduce at the same rate - and have no phenotype and
    can't influence their own copying rate in any way, then evolution will occur solely by drift. I'm
    not sure where Dawkins' views come in, though.

    > > I'm not sure about the "all" but I'm inclined to agree with the "most".
    > >
    > > Drift may have something to say about small populations on islands around speciation events -
    > > but it's probably a bit player in most other places - as far as the *features* of organisms go
    > > (as opposed to the makeup of their genes).
    >
    > Is this all just a gut feeling on your part? That would be fine. I just want to know if there is
    > any reason your assertion should be persuasive to others.

    Drift is most effective when population sizes are small. Selection is most effective when population
    sizes are large. I reckon this fact (in conjunction with nature's population sizes) will often
    limit's drift's usefulness as an explanation for features of organisms.
    --
    __________
    |im |yler http://timtyler.org/ [email protected] Remove lock to reply.
     
  5. Anon.

    Anon. Guest

    dkomo wrote:
    > Tim Tyler wrote:
    >
    >>Another quotable bit:
    >>
    >>``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable (I
    >>would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    >>world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    >>Devil's Chaplain, p.85.
    >>
    >>I'm not sure about the "all" but I'm inclined to agree with the "most".
    >>
    >>Drift may have something to say about small populations on islands around speciation events - but
    >>it's probably a bit player in most other places - as far as the *features* of organisms go (as
    >>opposed to the makeup of their genes).
    >
    >
    > Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
    > skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
    > old age, have different reactions to medications, have different physical abilities like being
    > able to run for long distances, sing very well, be really strong, and so on and so on -- these are
    > all the result of adaptations and natural selection?
    >
    Why not? Their ancestors have experienced different environments, so hte selective pressures will be
    different. Add into the mix variation in the environment (which can help maintain polymorphism), and
    disruptive selection, we have plenty of adaptive explanations for the diversity we see.

    Of course, drift may also be an explanation, but I believe that we can only separate out the
    contributions of the different causes empirically.

    Bob

    --
    Bob O'Hara

    Dept. of Mathematics and Statistics
    P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
    Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: http://www.RNI.Helsinki.FI/~boh/ Journal
    of Negative Results - EEB: http://www.jnr-eeb.org
     
  6. Tim Tyler

    Tim Tyler Guest

    dkomo <[email protected]> wrote or quoted:
    > Tim Tyler wrote:

    > > Another quotable bit:
    > >
    > > ``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
    > > (I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    > > world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    > > Devil's Chaplain, p.85.
    > >
    > > I'm not sure about the "all" but I'm inclined to agree with the "most".
    > >
    > > Drift may have something to say about small populations on islands around speciation events -
    > > but it's probably a bit player in most other places - as far as the *features* of organisms go
    > > (as opposed to the makeup of their genes).
    >
    > Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
    > skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
    > old age, have different reactions to medications, have different physical abilities like being
    > able to run for long distances, sing very well, be really strong, and so on and so on -- these are
    > all the result of adaptations and natural selection?

    Drift and selecion are theories of *evolutionary change*. You are just talking about variation.

    There can be as much variation in a population you like without the structure of the population
    changing over time.

    Also, merely pointing out the existence of variation in a trait does not demonstrate it is neutral
    (or near enough neutral to be subject to drift) - since:

    * there is such a thing as frequency-dependent selection;
    * most of the members of the population will not be long-term ancestors - and any variation they
    exhibit is of pretty low relevance;

    The second point grows in force when you take a gene's eye view.

    Of your examples, I would identify the best one as "eye colour".

    There /may/ be a case that eye colour is the subject of drift.

    ***If*** so, eye colour would be one of the things I classified as a "minor feature".

    However I am not convinced that eye colour is anywhere remotely *near* neutral.

    existence of variation in it can be explained adaptively by the hypothesis that those with unusual
    iris colours tend to be preferred mates.

    Further, there is geographic variation in the trait - which suggests to me adaptation as a
    sun-shield.

    If eye colour is *not* significantly under the influence of selection, how come nature has chosen
    bright pure pigments for the irises of the eyes of many people's in northern regions - while
    ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the equator and were
    most exposed to the sun?

    In summary, I think there are plenty of signs that iris colouration is strongly adaptive.

    Where is the evidence that the spectrum of iris colourations observed in human populations is
    due to drift?
    --
    __________
    |im |yler http://timtyler.org/ [email protected] Remove lock to reply.
     
  7. Tim Tyler wrote:

    > Drift is most effective when population sizes are small. Selection is most effective when
    > population sizes are large. I reckon this fact (in conjunction with nature's population sizes)
    > will often limit's drift's usefulness as an explanation for features of organisms.

    What is "drift"? Genes mutate randomly, malign mutations die out, mutations that have no effect on
    an organism don't really matter and beneficial mutations propagate and supplant organisms without
    that mutation. This generally leads to a new species, in time. But what's "drift"?

    --Jeff

    --
    Ho, ho, ho, hee, hee, hee and a couple of ha, ha, has; That's how we pass the day away, in the merry
    old land of Oz.
     
  8. Tim Tyler

    Tim Tyler Guest

    Anon. <[email protected]> wrote or quoted:

    > Of course, drift may also be an explanation, but I believe that we can only separate out the
    > contributions of the different causes empirically.

    It may be hard to do - but should be possible in principle:

    If you used a large population and "stirred" it well, the effects of drift would become very small
    compared to selection.

    You could similarly create circumstances that emphasised drift - small populations - with death
    striking young individuals at random.

    These sorts of experiments or observations should - in principle - have the power to tease out the
    effects of drift and selection empirically - and distinguish between hypotheses about to what extent
    the forces contribute to the forms of organisms.

    In theory, drift can help populations escape local maxima that selection would leave them stuck
    on. Quantifying that effect seems like an important task for the participants in the drift vs
    selection debate.
    --
    __________
    |im |yler http://timtyler.org/ [email protected] Remove lock to reply.
     
  9. Larry Moran

    Larry Moran Guest

    On Tue, 24 Feb 2004 20:57:29 +0000 (UTC),
    Tim Tyler <[email protected]> wrote:

    [snip]

    > Where is the evidence that the spectrum of iris colourations observed in human populations is due
    > to drift?

    It's probably hidden in the same place as the evidence that it's due to natural selection.

    Larry Moran
     
  10. Larry Moran

    Larry Moran Guest

    On Tue, 24 Feb 2004 20:57:28 +0000 (UTC), Anon.
    <[email protected]> wrote:
    > dkomo wrote:
    >> Tim Tyler wrote:

    [snip]

    >>>Drift may have something to say about small populations on islands around speciation events - but
    >>>it's probably a bit player in most other places - as far as the *features* of organisms go (as
    >>>opposed to the makeup of their genes).
    >>
    >> Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
    >> skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
    >> old age, have different reactions to medications, have different physical abilities like being
    >> able to run for long distances, sing very well, be really strong, and so on and so on -- these
    >> are all the result of adaptations and natural selection?
    >>
    > Why not? Their ancestors have experienced different environments, so hte selective pressures will
    > be different. Add into the mix variation in the environment (which can help maintain
    > polymorphism), and disruptive selection, we have plenty of adaptive explanations for the
    > diversity we see.
    >
    > Of course, drift may also be an explanation, but I believe that we can only separate out the
    > contributions of the different causes empirically.

    Yes. Until we can actually test the hypotheses it's wise not to *assume* that all morphological
    features are adaptations, don't you think?

    Tim seems to be making the default assumption that most morphological features are due to natural
    selection. Dawkins certainly makes that assumption. Is this valid?

    Larry Moran
     
  11. Guy Hoelzer

    Guy Hoelzer Guest

    in article [email protected], Tim Tyler at [email protected]
    wrote on 2/23/04 7:53 PM:

    > Guy Hoelzer <[email protected]> wrote or quoted:
    >> in article [email protected], Tim Tyler at [email protected]
    >
    >>> Another quotable bit:
    >>>
    >>> ``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
    >>> (I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    >>> world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    >>> Devil's Chaplain, p.85.
    >>
    >> IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
    >> "evolution" in complex dynamical systems that seemingly lack the basic ingredients for the
    >> process of natural selection (e.g., populations of reproducing agents), they will look
    >> increasingly like closed-minded zealots as time goes on. At this point, I think it is absurd and
    >> telling that Dawkins begins his argument with such a false premise as "Darwinian selection
    >> remains the only explanation for adaptive evolution."
    >
    > I can't really make out what you are on about here.

    Sorry. My argument got drowned out by my anti-Dawkins rant.

    > It seems as though you are asserting that "populations of reproducing agents" "lack the basic
    > ingredients for the process of natural selection".
    >
    > That doesn't seem to make much sense.

    Nor I. It is not what I meant to say. What I meant was that natural selection is a mechanism of
    adaptive evolution exhibited by "populations of reproducing agents", but no justification has ever
    been offered AFAIK for the position that it is the only possible mechanism in this context. Now that
    it is clear that optimizing, adaptive processes occur in all sorts of contexts, manifesting an array
    of mechanisms, I think the view espoused by Dawkins above is no longer tenable.

    > Or maybe you are saying that evolution (of a sort) can occur in some systems which "lack the basic
    > ingredients for the process of natural selection".

    Yes. This is part of my view.

    > I guess that is true in theory - e.g. if you have a hypothetical system - where agents all
    > reproduce at the same rate - and have no phenotype and can't influence their own copying rate
    > in any way, then evolution will occur solely by drift. I'm not sure where Dawkins' views come
    > in, though.

    Right. This is all fine, but off the point and not what I meant to say. My point was that natural
    selection is not the only possible adaptive process.

    >>> I'm not sure about the "all" but I'm inclined to agree with the "most".
    >>>
    >>> Drift may have something to say about small populations on islands around speciation events -
    >>> but it's probably a bit player in most other places - as far as the *features* of organisms go
    >>> (as opposed to the makeup of their genes).
    >>
    >> Is this all just a gut feeling on your part? That would be fine. I just want to know if there is
    >> any reason your assertion should be persuasive to others.
    >
    > Drift is most effective when population sizes are small. Selection is most effective when
    > population sizes are large. I reckon this fact (in conjunction with nature's population sizes)
    > will often limit's drift's usefulness as an explanation for features of organisms.

    You must also be making an implicit assumption about the typical strength of selection in natural
    populations, because drift operates in all finite populations of any size. In other words, drift can
    dominate weak selection in large populations, and even strong selection in small populations (e.g.
    mutational meltdown). The balance between the influences of drift an selection was explored
    explicitly in Ota's Nearly Neutral model.

    So what is the basis for your expectation that selection is usually strong enough to relegate drift
    to being a "bit player" in natural populations?

    Cheers,

    Guy
     
  12. Dkomo

    Dkomo Guest

    Tim Tyler wrote:
    >
    > dkomo <[email protected]> wrote or quoted:
    > > Tim Tyler wrote:
    >
    > > > Another quotable bit:
    > > >
    > > > ``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
    > > > (I would argue) that most if not all the evolutionary changes we actually see in the
    > > > macroscopic world (as opposed to those concealed among the molecules) are adaptive and
    > > > Darwinian.'' - A Devil's Chaplain, p.85.
    > > >
    > > > I'm not sure about the "all" but I'm inclined to agree with the "most".
    > > >
    > > > Drift may have something to say about small populations on islands around speciation events -
    > > > but it's probably a bit player in most other places - as far as the *features* of organisms go
    > > > (as opposed to the makeup of their genes).
    > >
    > > Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
    > > skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases
    > > in old age, have different reactions to medications, have different physical abilities like
    > > being able to run for long distances, sing very well, be really strong, and so on and so on --
    > > these are all the result of adaptations and natural selection?
    >
    > Drift and selecion are theories of *evolutionary change*. You are just talking about variation.
    >
    > There can be as much variation in a population you like without the structure of the population
    > changing over time.
    >

    That's what I'm getting at. Drift and selection are not the only alternatives. It's possible to have
    *no* selection and *no* drift (if the population is large). The allele frequencies will remain
    constant according to the Hardy-Weinberg Law.

    > Also, merely pointing out the existence of variation in a trait does not demonstrate it is neutral
    > (or near enough neutral to be subject to drift) - since:
    >

    Neither does pointing out the existence of a trait demonstrate that it is an adaptation that
    occurred in the past. People who believe that most or all features of organisms have been selected
    for are known as "panadaptationists." Dawkins is certainly one. Gould certainly was not. I was under
    the impression that panadaptationism is frowned upon these days by most evolutionists.

    I think many of the traits I pointed out are either what Gould called "spandrels":

    http://spandrel.com/about.html

    or they are neutral mutations that have persisted within human populations for a very long time.
    They are *not* adaptations to anything.

    > * there is such a thing as frequency-dependent selection;
    > * most of the members of the population will not be long-term ancestors - and any variation they
    > exhibit is of pretty low relevance;
    >
    > The second point grows in force when you take a gene's eye view.
    >
    > Of your examples, I would identify the best one as "eye colour".
    >
    > There /may/ be a case that eye colour is the subject of drift.
    >

    Why does it have to be the subject of drift? It could simply be an allele which is not under
    selection and whose frequency remains pretty constant in a particular human subpopulation.

    > ***If*** so, eye colour would be one of the things I classified as a "minor feature".
    >
    > However I am not convinced that eye colour is anywhere remotely *near* neutral.
    >

    > existence of variation in it can be explained adaptively by the hypothesis that those with unusual
    > iris colours tend to be preferred mates.
    >
    > Further, there is geographic variation in the trait - which suggests to me adaptation as a
    > sun-shield.
    >
    > If eye colour is *not* significantly under the influence of selection, how come nature has chosen
    > bright pure pigments for the irises of the eyes of many people's in northern regions - while
    > ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the equator and
    > were most exposed to the sun?
    >
    > In summary, I think there are plenty of signs that iris colouration is strongly adaptive.
    >

    It could be. I'm not the diametric opposite of a panadaptationist, as one well known poster to this
    group is, but I do insist that the burden of proof lies with those who claim that particular traits
    are adaptations. You made an argument about eye color, but you don't have any empirical proof. And
    this, unfortunately, is the case with most features of organisms. We simply have no direct proof
    that they are in fact adaptations, even though we accept the principles of variation and selection.

    > Where is the evidence that the spectrum of iris colourations observed in human populations is due
    > to drift?

    False dichotomy. It's not selection *or* drift (or even both operating at the same time). Iris
    colourations could simply be neural traits that are subject to neither, being in Hardy-Weinberg
    equilibrium.

    [email protected]
     
  13. Dkomo

    Dkomo Guest

    "Anon." wrote:
    >
    > dkomo wrote:
    > > Tim Tyler wrote:
    > >
    > >>Another quotable bit:
    > >>
    > >>``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
    > >>(I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    > >>world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    > >>Devil's Chaplain, p.85.
    > >>
    > >>I'm not sure about the "all" but I'm inclined to agree with the "most".
    > >>
    > >>Drift may have something to say about small populations on islands around speciation events -
    > >>but it's probably a bit player in most other places - as far as the *features* of organisms go
    > >>(as opposed to the makeup of their genes).
    > >
    > >
    > > Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
    > > skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases
    > > in old age, have different reactions to medications, have different physical abilities like
    > > being able to run for long distances, sing very well, be really strong, and so on and so on --
    > > these are all the result of adaptations and natural selection?
    > >
    > Why not? Their ancestors have experienced different environments, so hte selective pressures will
    > be different. Add into the mix variation in the environment (which can help maintain
    > polymorphism), and disruptive selection, we have plenty of adaptive explanations for the
    > diversity we see.
    >

    Bah! Sounds like panadaptationism. See my reply to Tim Tyler.

    We have plenty of "just so" stories to explain each and every purported adaptation. Any amateur
    evolution theorist can come up with half a dozen armchair explanations for each such trait. What we
    don't have in most cases is empirical proof that a particular feature of an organisn is indeed an
    adaptation to the environment.

    > Of course, drift may also be an explanation, but I believe that we can only separate out the
    > contributions of the different causes empirically.
    >

    It may be that many features of organisms are incidental and play no role in their evolution. That
    doesn't necessarily imply that these features are subject to drift. Drift is a phenomenon of small,
    isolated populations.

    [email protected]
     
  14. John Edser

    John Edser Guest

    > Dawkins quote: ``Darwinian selection remains the only explanation for adaptive evolution - and it
    > is arguable (I would argue) that most if not all the evolutionary changes we actually see in the
    > macroscopic world (as opposed to those concealed among the molecules) are adaptive and
    > Darwinian.'' - A Devil's Chaplain, p.85.

    GH:- IMHO, if Dawkins and his followers continue to ignore the overwhelming evidence of adaptive
    "evolution" in complex dynamical systems that seemingly lack the basic ingredients for the process
    of natural selection (e.g., populations of reproducing agents), they will look increasingly like closed-
    minded zealots as time goes on. At this point, I think it is absurd and telling that Dawkins begins
    his argument with such a false premise as "Darwinian selection remains the only explanation for
    adaptive evolution."

    JE:- Darwinian selection _does_ remain the only _testable_ explanation for adaptive evolution.
    However, Dawkins et al have NOT represented the Darwinian argument, they have only represented the
    Hamiltonian argument which is competitive to the Darwinian argument. It is entirely incorrect to
    suggest that gene centric Neo Darwinism somehow represents Darwin's original theory of evolution by
    natural selection.

    The Hamiltonian argument fails because empirically, genes only have a _dependent_ fitness. What are
    they entirely fitness dependent on? The Darwinian _fertile_ organism level of selection. Hamilton
    _artificially_ split the single Darwinian fertile organism level into two independent levels within
    just an over simplified model allowing just a hypothetical gene level of selection to compete and
    win against the empirical Darwinian level forcing organism fitness altruism. Hamilton's model
    deleted all genetic epistasis whereas the Darwinian argument included it.

    > I'm not sure about the "all" but I'm inclined to agree with the "most". Drift may have something
    > to say about small populations on islands around speciation events - but it's probably a bit
    > player in most other places - as far as the *features* of organisms go (as opposed to the makeup
    > of their genes).

    GH:- Is this all just a gut feeling on your part? That would be fine. I just want to know if there
    is any reason your assertion should be persuasive to others.

    JE:- Sampling error is just a random event. This being the case, it can only be validly supposed to
    cause temporal variation and not evolution. Once you allow sampling error as causative to evolution
    within evolutionary theory, you reduce this theory to a non testable status. The testability of
    evolution by Darwinian natural selection is not removed if sampling error is regarded as either
    random or non random _variation_ because variation is not causative to evolution it is just one of
    many limiting factors within the Darwinian theory of evolution.

    Regards,

    John Edser Independent Researcher

    PO Box 266 Church Pt NSW 2105 Australia

    [email protected]
     
  15. in article [email protected], Tim Tyler at [email protected]
    wrote on 25/2/04 9:57 AM:

    > If eye colour is *not* significantly under the influence of selection, how come nature has chosen
    > bright pure pigments for the irises of the eyes of many people's in northern regions - while
    > ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the equator and
    > were most exposed to the sun?
    >
    > In summary, I think there are plenty of signs that iris colouration is strongly adaptive

    The genetics of eye colour are not yet well understood
    http://www.athro.com/evo/gen/inherit1.html#uncertainty But even if there is selection for eye
    colour. Which genes contribute to that phenotype is probably the result of a kind of genetic drift
    unless the population contained all possible mutations that could contribute to to the desired
    phenotype at the same time. That is, for selection of the sequence that was best at giving the brown
    eye colour phenotype, to occur. The population would have to be infinite. Selection acts on
    phenotype, the neutral theory applies to genotype.
    --

    Phillip Smith [email protected] replace bugger with ihug http://www.applied-evolution.co.nz

    "he who is smeared with blubber has the kindest heart" -- a Greenland Eskimo adage
     
  16. Tim Tyler

    Tim Tyler Guest

    dkomo <[email protected]> wrote or quoted:
    > Tim Tyler wrote:
    > > dkomo <[email protected]> wrote or quoted:
    > > > Tim Tyler wrote:

    > > > > Drift may have something to say about small populations on islands around speciation events
    > > > > - but it's probably a bit player in most other places - as far as the *features* of
    > > > > organisms go (as opposed to the makeup of their genes).
    > > >
    > > > Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat
    > > > or skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different
    > > > diseases in old age, have different reactions to medications, have different physical
    > > > abilities like being able to run for long distances, sing very well, be really strong, and so
    > > > on and so on -- these are all the result of adaptations and natural selection?
    > >
    > > Drift and selecion are theories of *evolutionary change*. You are just talking about variation.
    > >
    > > There can be as much variation in a population you like without the structure of the population
    > > changing over time.
    >
    > That's what I'm getting at. Drift and selection are not the only alternatives. It's possible to
    > have *no* selection and *no* drift (if the population is large). The allele frequencies will
    > remain constant according to the Hardy-Weinberg Law.

    Large populations slow down - but don't eliminate - drift.

    You only get no drift in an infinite population - and then it makes no sense to talk about gene
    frequencies at all.

    > > Also, merely pointing out the existence of variation in a trait does not demonstrate it is
    > > neutral (or near enough neutral to be subject to drift) - since:
    >
    > Neither does pointing out the existence of a trait demonstrate that it is an adaptation that
    > occurred in the past.

    Of course.

    > People who believe that most or all features of organisms have been selected for are known as
    > "panadaptationists."

    Genetic drift is enough to indicate than not all features of organisms have necessarily been
    selected for.

    Attributing "most" things to selection seems quite reasonable to me, though.

    > I was under the impression that panadaptationism is frowned upon these days by most evolutionists.

    Adaptations are certainly all over the place.

    "Panadaptationism" is - or ought to mean "adaptations everywhere" - but exactly how common that is
    supposed to mean isn't clear.

    The word doesn't seem to be in the dictionary - has anyone actually bothered to define it - or is it
    just a term of derision?

    > I think many of the traits I pointed out are either what Gould called "spandrels":
    >
    > http://spandrel.com/about.html
    >
    > or they are neutral mutations that have persisted within human populations for a very long time.
    > They are *not* adaptations to anything.

    Most of your traits were statements about the existence of variation within in a trait.

    You mentioned: brown, green, or blue eyes, being short or tall, being fat or skinny, being beautiful
    or ugly, having red, black or blonde hair - and so on.

    I've discussed eye colour already. Height is an adaptive trait - perhaps with some frequency
    dependent selection for different heights being caused by the existence of different
    lifestyles. Similarly with weight. Also, a fair bit of the observed variation in both traits is
    not genetic at all.

    Beauty is adaptive - and being ugly is mal-adaptive - and exists through being constantly generated
    - and not yet having been weeded out. Hair colour is also adaptive. Black hair protects against UV
    radiation - and that's why all African types have black hair (except a few albinos who soon get
    ill). Red and blond hair are (I claim) clearly the result

    > > * there is such a thing as frequency-dependent selection;
    > > * most of the members of the population will not be long-term ancestors - and any variation they
    > > exhibit is of pretty low relevance;
    > >
    > > The second point grows in force when you take a gene's eye view.
    > >
    > > Of your examples, I would identify the best one as "eye colour".
    > >
    > > There /may/ be a case that eye colour is the subject of drift.
    >
    > Why does it have to be the subject of drift? It could simply be an allele which is not under
    > selection and whose frequency remains pretty constant in a particular human subpopulation.

    If the population is finite, it will drift.

    > > ***If*** so, eye colour would be one of the things I classified as a "minor feature".
    > >
    > > However I am not convinced that eye colour is anywhere remotely *near* neutral.
    > >

    > > existence of variation in it can be explained adaptively by the hypothesis that those with
    > > unusual iris colours tend to be preferred mates.
    > >
    > > Further, there is geographic variation in the trait - which suggests to me adaptation as a sun-
    > > shield.
    > >
    > > If eye colour is *not* significantly under the influence of selection, how come nature has
    > > chosen bright pure pigments for the irises of the eyes of many people's in northern regions -
    > > while ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the
    > > equator and were most exposed to the sun?
    > >
    > > In summary, I think there are plenty of signs that iris colouration is strongly adaptive.
    >
    > It could be. I'm not the diametric opposite of a panadaptationist, as one well known poster to
    > this group is, but I do insist that the burden of proof lies with those who claim that particular
    > traits are adaptations.

    Hmm. It seems to me that whenever I get into a discussion there's always someone who claims that the
    burden of proof lies on my side.

    Nine times out of ten I can't see why that is the case - and this is one of them.

    I suggest "adaptation" should *normally* be the default hypothesis - because adaptation has shown
    itself to be the best, most powerful theory for accounting for the forms of organisms.

    That's not to say that it's responsible for *everything* - but that - if anything - the burden of
    proof ought to normally be on the drift side of the fence - since drift typically hasn't been shown
    to be responsible for very much of anything.

    > You made an argument about eye color, but you don't have any empirical proof.

    ...but I could soon find some on request. The dark eyes of african populations is a well known fact
    - and has no explanation under the hypothesis that iris colour is subject to drift.

    eye colour being adaptive, though ;-)

    Frequency-dependent selection favouring rare eye colours has been demonstrated in Drosophila
    melanogaster - I believe - in:

    ``Minority mating advantage of certain eye color mutants of Drosophila
    melanogaster. IV. Female discrimination among three genotypes.''

    - http://calorierestriction.org/pmid/?n=3115250

    ...but this just demonstrates that the idea is plausible - not that it is responsible for the
    observed human variation.
    --
    __________
    |im |yler http://timtyler.org/ [email protected] Remove lock to reply.
     
  17. Tim Tyler

    Tim Tyler Guest

    phillip smith <[email protected]> wrote or quoted:
    > Tim Tyler at [email protected] wrote on 25/2/04 9:57 AM:

    > > If eye colour is *not* significantly under the influence of selection, how come nature has
    > > chosen bright pure pigments for the irises of the eyes of many people's in northern regions -
    > > while ensuring a hefty dark melanin pigment in those whose ancestors lived closest to the
    > > equator and were most exposed to the sun?
    > >
    > > In summary, I think there are plenty of signs that iris colouration is strongly adaptive
    >
    > The genetics of eye colour are not yet well understood
    > http://www.athro.com/evo/gen/inherit1.html#uncertainty But even if there is selection for eye
    > colour. Which genes contribute to that phenotype is probably the result of a kind of genetic drift
    > unless the population contained all possible mutations that could contribute to to the desired
    > phenotype at the same time. That is, for selection of the sequence that was best at giving the
    > brown eye colour phenotype, to occur. The population would have to be infinite. Selection acts on
    > phenotype, the neutral theory applies to genotype.

    That doesn't seem to make any sense. This bit:

    "for selection of the sequence that was best at giving the brown eye colour phenotype, to occur. The
    population would have to be infinite.''

    ...and this bit:

    "Which genes contribute to that phenotype is probably the result of a kind of genetic drift unless
    the population contained all possible mutations that could contribute to to the desired phenotype at
    the same time."

    ...don't add up as arguments. Can you say what you mean more clearly?
    --
    __________
    |im |yler http://timtyler.org/ [email protected] Remove lock to reply.
     
  18. Anon.

    Anon. Guest

    dkomo wrote:
    > Tim Tyler wrote:
    >
    <snip>
    > Why does it have to be the subject of drift? It could simply be an allele which is not under
    > selection and whose frequency remains pretty constant in a particular human subpopulation.
    >
    <snip>
    >
    >>Where is the evidence that the spectrum of iris colourations observed in human populations is due
    >>to drift?
    >
    >
    > False dichotomy. It's not selection *or* drift (or even both operating at the same time). Iris
    > colourations could simply be neural traits that are subject to neither, being in Hardy-Weinberg
    > equilibrium.
    >
    OK, hands up all those who have studied the assumptions for HWE and still believe that it's a good
    model of reality?

    In this particular case, the fact that the population is finite (and the sub-populations are
    smaller) means that drift WILL occur. It's just a fact of life (and death). And it's difficult to
    see how you can have a polymorphism without one of the two acting at some stage.

    Bob

    --
    Bob O'Hara

    Dept. of Mathematics and Statistics
    P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
    Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: http://www.RNI.Helsinki.FI/~boh/ Journal
    of Negative Results - EEB: http://www.jnr-eeb.org
     
  19. Anon.

    Anon. Guest

    Tim Tyler wrote:
    > Anon. <[email protected]> wrote or quoted:
    >
    >
    >>Of course, drift may also be an explanation, but I believe that we can only separate out the
    >>contributions of the different causes empirically.
    >
    >
    > It may be hard to do - but should be possible in principle:
    >
    > If you used a large population and "stirred" it well, the effects of drift would become very small
    > compared to selection.
    >
    > You could similarly create circumstances that emphasised drift - small populations - with death
    > striking young individuals at random.
    >
    > These sorts of experiments or observations should - in principle - have the power to tease out the
    > effects of drift and selection empirically - and distinguish between hypotheses about to what
    > extent the forces contribute to the forms of organisms.
    >
    > In theory, drift can help populations escape local maxima that selection would leave them stuck
    > on. Quantifying that effect seems like an important task for the participants in the drift vs
    > selection debate.

    SBT anyone? There's been a lot of discussion about this (its called the Shifting Balance Theory).
    The problem is that the theory is so complex that it's difficult to show all the bits working at the
    same time. My own opinion is that SBT probably isn't very important, because if it was, we would
    have plenty of examples of it by now. Scientific, huh?

    Bob

    --
    Bob O'Hara

    Dept. of Mathematics and Statistics
    P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
    Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: http://www.RNI.Helsinki.FI/~boh/ Journal
    of Negative Results - EEB: http://www.jnr-eeb.org
     
  20. Anon.

    Anon. Guest

    dkomo wrote:
    > "Anon." wrote:
    >
    >>dkomo wrote:
    >>
    >>>Tim Tyler wrote:
    >>>
    >>>
    >>>>Another quotable bit:
    >>>>
    >>>>``Darwinian selection remains the only explanation for adaptive evolution - and it is arguable
    >>>>(I would argue) that most if not all the evolutionary changes we actually see in the macroscopic
    >>>>world (as opposed to those concealed among the molecules) are adaptive and Darwinian.'' - A
    >>>>Devil's Chaplain, p.85.
    >>>>
    >>>>I'm not sure about the "all" but I'm inclined to agree with the "most".
    >>>>
    >>>>Drift may have something to say about small populations on islands around speciation events -
    >>>>but it's probably a bit player in most other places - as far as the *features* of organisms go
    >>>>(as opposed to the makeup of their genes).
    >>>
    >>>
    >>>Really? You mean the fact that people have brown, green, or blue eyes, are short or tall, fat or
    >>>skinny, beautiful or ugly, have red, black or blonde hair, are prone to get different diseases in
    >>>old age, have different reactions to medications, have different physical abilities like being
    >>>able to run for long distances, sing very well, be really strong, and so on and so on -- these
    >>>are all the result of adaptations and natural selection?
    >>>
    >>
    >>Why not? Their ancestors have experienced different environments, so hte selective pressures will
    >>be different. Add into the mix variation in the environment (which can help maintain
    >>polymorphism), and disruptive selection, we have plenty of adaptive explanations for the
    >>diversity we see.
    >>
    >
    >
    > Bah! Sounds like panadaptationism. See my reply to Tim Tyler.
    >
    > We have plenty of "just so" stories to explain each and every purported adaptation. Any amateur
    > evolution theorist can come up with half a dozen armchair explanations for each such trait. What
    > we don't have in most cases is empirical proof that a particular feature of an organisn is indeed
    > an adaptation to the environment.
    >
    Yes, so we need empirical observation to resolve this argument. My point is that we know that
    spatial and temporal variation in selection pressures occurs, so we can't rule them out just because
    we don't like them. Examining their effects is difficult (I've looked at both. One study needed a 60
    year time seies, the other merely a crossing experiment with a couple of thousand frogs).

    >
    >>Of course, drift may also be an explanation, but I believe that we can only separate out the
    >>contributions of the different causes empirically.
    >>
    >
    >
    > It may be that many features of organisms are incidental and play no role in their evolution. That
    > doesn't necessarily imply that these features are subject to drift. Drift is a phenomenon of
    > small, isolated populations.
    >
    And there are a lot of them about, even in organisms like insects.

    Bob

    --
    Bob O'Hara

    Dept. of Mathematics and Statistics
    P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
    Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: http://www.RNI.Helsinki.FI/~boh/ Journal
    of Negative Results - EEB: http://www.jnr-eeb.org
     
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