Re: Macro- and microevolution [was Re: Icons of Evolution]

From: Paul Nelson (
Date: Mon Jun 18 2001 - 10:46:46 EDT

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    Todd Greene wrote:

    >And this is all beside the primary point, which is
    >that there is nothing other than the "microevolutionary"
    >processes involved in genetic inheritance in a species
    >population, and interactions with other species
    >in an ecosystem, that has been yet found to be
    >needed to account for evolutionary change.

    You will find many evolutionary biologists
    disagreeing with you. They would contend that
    standard neo-Darwinian theory does not, in
    fact, explain macroevolutionary change, because
    the former treats types of variation that are
    causally insufficient to modify (for instance)
    animal morphology in the ways required by the
    theory of common descent.

    Here's an example, from a new book I highly

    "...the evolutionary theory [neo-Darwinism] that
    grew up before the advent of regulatory molecular
    biology dealt with the problem of the origin of
    novel morphological structures in two ways. The
    first has been to treat the mechanisms generating
    novel morphological structures as a black box.
    New forms were considered to arise 'because'
    the environment changed. But while changes in
    Precambrian or Ordovician weather, continental
    shifts, or temperature may have contributed crucial
    selective forces, they do not generate heads or
    appendicular forms; only genes do that. The
    second mode of classical argument was that
    organismal evolution is the product of minute
    changes in genes and gene products, which
    occur as point mutations and which accumulate
    little by little, providing the opportunity for
    selection and ultimately reproductive isolation.
    The major forms this argument has taken have
    focused on stepwise, adaptive changes in
    protein sequence, but this is probably largely
    irrelevant to the evolution of any salient features
    of animal morphology (see, e.g., Miklos 1993)."

    [from Eric H. Davidson, _Genomic Regulatory
    Systems: Development and Evolution_ (New York:
    Academic Press, 2001), pp. 19-20]

    The molecular geneticist Susan Lindquist at
    the University of Chicago tends to begin her
    recent major papers with statements to the
    effect that "the problem of macroevolution is
    unsolved." Such statements are common in
    the evolutionary literature. They would not be
    so if your argument, namely, that our present
    knowledge of microevolution is sufficient to
    explain macroevolution, were true.

    Paul Nelson
    Senior Fellow
    The Discovery Institute

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