RE: Dawkins & Convergent Evolution- the final word (?)

From: Vincent Campbell (
Date: Wed Aug 29 2001 - 11:36:13 BST

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    From: Vincent Campbell <>
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    Subject: RE: Dawkins & Convergent Evolution- the final word (?)
    Date: Wed, 29 Aug 2001 11:36:13 +0100
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    >> Even without looking at their genes, the fact that they've
    >> followed different paths is evident in their differences- the
    >> collective example being marsupials.

            <Of course there are differences. Why shouldn't there be?>

            There should only be no differences if you're argument is correct
    that perfectly convergent evolution is evidence of MR. Of course there's no
    such thing, but you don't seem to see how that kicks the argument's legs
    from under it.

    > < They're different species in different locations. But they're also
    > profoundly similar. This
    > is perhaps a better example of parallel evolution (a term now in wide
    > currency), since the starting points for these ant-eaters, moles, flying
    > squirrels, cats, wolves, mice, jerboas, etc., were the same tree shrews
    > that
    > diverged 110 million years ago into marsupials and placentals. Parallel
    > evolution is quite common and crops up in human origins. Witness the
    > incredibly similar development of Eurasian Homo sapiens (Neanderthal) and
    > the African model.>
            Neanderthals were not modern humans, and there were distinct
    physiological differences, and indications of differential intellectual
    ability also. The reasons for these differences are climatic, with Ice Age
    Europe being very different from Africa.

            <I do understand the point you're making about Dawkins. He applies
    > phrase "vanishingly improbable" not to convergence as it actually occurs
    > but
    > to some sort of imaginary, ideal convergence. In other words, he's saying
    > nothing, which is why the passage is so confusing. >
            Clearly, it's confusing to you. He's explaining how similar
    environments can result in organisms pursuing very similar lifestyles (e.g.
    carnivore, herbivore) and that, superficially such organisms can look very
    similar, but it's the differences that demonstrate the different
    evolutionary pathways that the organisms have followed. I don't see how it
    could be any clearer.

            <In fact, convergence as
    > it actually occurs is vanishingly improbable even when natural selection
    > is
    > involved. And there are many examples in which natural selection plays no
    > conceivable role.>
            Yeah right. If you say so.

            <F. W. Went studied convergence among shrubs in New Zealand. He
    found about
    > 50 species of shrubs that had independently developed the same pattern of
    > "interlaced, tortuous branches and reduced leaves." This would presumably
    > have protected them from herbivores. But there are no herbivores native
    > to
    > New Zealand. Moreover, this pattern "occurs in so many shrubs from
    > different habitats, it does not seem to be an adaptation to the
    > environment." He provides several other examples of convergence which he
    > contends cannot be explained by natural selection. He argues that the
    > chromosomes associated with these traits must have somehow hopped across
    > species. (Went, "Parallel Evolution," Taxon 20:197-226, 1971.)>
            This smacks of a combination of simple assumption and limited
    imagination. Why assume it's a response to protect themselves from
    herbivores? What about an environmental impact in combination with drift
    amongst an isolated population of related species? Again with the
    generation old studies, with no thought to possible empirical answers.

            <Bernhard Rensch studied butterflies with similar color
    > patterns on their wings. Some of these could be explained by mimicry of
    > butterflies avoided by predators. But often these similar patterns appear
    > on butterflies in completely different places in which such mimicry would
    > be
    > useless. (Rensch, Evolution Above the Species Level, Methuen, 1959.)>
            This is akin to creationists arguing that plants that look like
    insects, and vice versa are proof of design etc. A book from the 1950s....
    Again, similarity doesn't mean the same, does not need any other mechanism
    that natural selection, as long as it's understood what that entails.

            <In the February 1999 issue of Scientific American, Stiassny and
    > discuss the inexplicable similarity of color patterns on the scales of
    > cichlids in separate African lakes.>
            Now that's a better one. I'll check it out. I wonder if you've
    liberally mis-read this as you clearly did with Dawkins....


            <I'm looking for documentation of more examples.>

            Good for you.


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