Re: Darwin quote

From: Keith Miller (kbmill@ksu.edu)
Date: Wed Aug 13 2003 - 21:11:33 EDT

  • Next message: Jay Willingham: "Re: different thread"

    On Wednesday, August 13, 2003, at 10:18 AM, Walter Hicks wrote:

    > I agree that all of these (and ones offered by Terry) affect
    > evolution, but I don't see most of them as alternatives to natural
    > selection. For the most part they introduce variation and then natural
    > selection filters out the ones that are not useful for survival.
    > Catastrophic changes are an exception and certainly would represent a
    > non-"Darwinian" effect.

    Firstly, the issue is not an either/or choice between natural selection
    and something else. The question is what is the relative importance of
    different processes under different circumstances and at different
    heirarchical scales. Natural selection is always operative -
    although its impact may be masked by other processes.

    Genetic drift and the founder effect are examples where new mutations
    can be fixed in a population (usually small) without the filtering
    effect of natural selection. These processes may be especially
    significant during speciation. Sexual selection is likely another
    important driver of evolutionary change.

    Another example at a larger scale is species selection. In this case
    lineages that have higher speciation rates would displace closely
    related lineages with low rates of speciation. The ultimate success of
    lineages in this case would not be controlled by natural selection
    which operates at the level of the individual.

    Major extinction events likely had very important impacts on the
    direction of evolution on a large scale. Such effects would be
    independent of natural selection.

    Keith

    Keith B. Miller
    Research Assistant Professor
    Dept of Geology, Kansas State University
    Manhattan, KS 66506-3201
    785-532-2250
    http://www-personal.ksu.edu/~kbmill/



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