Re: Convergence

From: Dace (
Date: Thu Aug 09 2001 - 20:33:51 BST

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    Subject: Re: Convergence
    Date: Thu, 9 Aug 2001 12:33:51 -0700
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    > > Dawkins discusses this dilemma in The Blind Watchmaker: "It is
    > > vanishingly improbable that the same evolutionary pathway should ever
    > > be followed twice. And it would seem similarly improbable, for the
    > > same statistical reasons, that two lines of evolution should converge
    > > on the same endpoint from different starting points. It is all the
    > > more striking... that numerous examples can be found in real nature,
    > > in which independent lines of eovlution appear to have converged, from
    > > very different starting points, on what looks very like the same
    > > end-point."

    Joe Dees wrote:

    > Random mutation (within the same range of genetic possibilities),
    > followed by selection by similar environments for similar niches
    > should just about do it.

    Are you establishing yourself as a higher authority on these matters than
    Dawkins? Of course, he's taking into consideration environmental fitness
    and random mutation in his assessment. Learn to pick your fights. Don't
    just assume that every assertion I make is unorthodox or subject to debate.

    Bill Spight wrote:

    > Dear Ted,
    > > It's well known that atavistic traits commonly pop up among developing
    > > organisms. A feral pig is liable to develop tusks. Horses occasionally
    > > grow extra toes. Humans are sometimes born with a small tail. Such
    > > can be expected if we do indeed resonate with past forms. But they can
    > > be explained according to the genetic model. What can't be explained
    > > genetically is parallel evolution, or "convergence."
    > Convergent evolution is in fact a major support of the theory of
    > evolution.

    And as Hume said, "The green table is green."

    > > Among plants and
    > > animals, we continually find new examples of organisms widely separated
    > > their phylogenetic derivation which nonetheless develop remarkably
    > > forms. In New Zealand we find many kinds of leaves common to Eurasia
    > > serve to fend off herbivores that don't exist in New Zealand. There
    > > to be no reason why marsupials and mammals would develop such incredibly
    > > similar forms.
    > Don't be silly.

    See Dawkins above. He may not accept morphic resonance, but at least he
    concedes that convergence is a mystery.

    > > Why should butterflies or fish of different species in
    > > different locations develop almost identical color patterns on their
    > > or scales? In some cases animals mimic others that are poisonous to
    > > predators and are thus avoided by predators along with the poisonous
    > > varieties. But this explanation fails to apply in the vast majority of
    > > cases.
    > >
    > > According to Sheldrake's model, organic systems resonate with similar
    > > systems. We resonate with ourselves individually, with our species, and
    > > with any other species which is similar enough to our own. If flying
    > > squirrels, jerboas, and moles are all emerging in both Australia and
    > > Eurasia, they will be drawn into similar evolutionary pathways due to
    > > resonance with each other. Outside of this model, there's no
    > > for convergent evolution.
    > >
    > Puleaze!
    > First, there is the simple explanation of similarity of environments.
    > Aquatic mammals and fish provide a basic example.
    > Second, there are physical and chemical constraints that impose
    > structure. Example: similarities in structure of sunflowers, pine cones,
    > snail and nautilus shells.
    > Third, there is coincidence.
    > You need to find characteristics that do not contribute to the fitness
    > of the organism, and are not similar for physical or chemical reasons
    > (such as minimizing the use of resources), and then compare their
    > occurrence with a model that indicates how often such convergences occur
    > at random, and show that they occur too often. Otherwise, don't waste
    > your time.

    To take a single example, the astonishingly similar color patterns on the
    scales of fish of different species which inhabit different African lakes
    cannot be explained by any known factor. It has nothing to do with fitness
    or chemistry. You've got nothing here except coincidence. And that's the
    point Dawins is making above. There's a colossal coincidence at work here,
    and it's repeated *countless* times across the earth. At least Dawkins is
    honest about the extreme improbability of neo-Darwinian theory.

    > The advent of computers has enabled us to see, by simulation, how
    > frequent random coincidences are. It is human nature to seek
    > explanations, and statistical argument alone leaves nagging doubts. Thus
    > people can easily believe that Design, whether by supernatural or by as
    > yet undiscovered natural means, is necessary to explain coincidences. It
    > appears that morphic resonance is one such principle of Design.

    Both creationism and neo-Darwinism are theories from design. In one case,
    the design exists in the mind of God. In the other other case, it exists in
    our chromosomes. The major alternatives to a design theory are Darwin
    himself-- who explicitly rejected the notion of a blueprint contained in our
    bodies-- and Sheldrake.

    It is
    > invoked without much consideration at all of other, scientific
    > explanation.

    Absolutely not. Sheldrake makes no claims without first carefully
    scrutinizing the alternatives. Apparently you're not familiar with his
    work. I recommend The Presence of the Past. The first eight chapters
    provide a nice intro to his theory as well as a fascinating account of the
    history of biological thought.

    > And it assumes that there is no coincidence.

    Sheldrake does not assume there's no such thing as coincidence. On the
    other hand, he doesn't assume that everything is explainable according to
    coincidence. Maybe this whole world is just an illusion. Maybe it's just a
    coincidence that when you drink water, you cease to feel thirsty. Or maybe
    some things are indeed explainable through reason and science.

    Ted Dace

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