Re: Evolution Statement (Finchs' beaks)

From: John Solum (jsolum@umich.edu)
Date: Sat Dec 08 2001 - 13:49:32 EST

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    >To continue, such an extrapolation is unwarranted because of the simple fact
    >that changes observed in STE studies and bacterial resistance are
    >_reversible_. While finch's beaks become more robust in times of drought
    >when seeds have tougher shells, they revert to the more slender shape when
    >climate returns to normal and seed shells less hard to crack. Such
    >reversibility disqualifies STE from serving as the mechanism of DWM, or at
    >least raises serious questions about it. The statement would be more
    >forthright and therefore improved if it acknowledged this.

    My comments:
    I don't see how changes in the finchs' beaks indicate that natural
    selection isn't a mechanism for descent with modification. During droughts
    the finches with larger beaks fare better than the smaller-beaked variety
    and so become more common. When the drought ends, the larger-beaked
    finches don't fare any better than the small-beaked variety (in other words
    the pressure that caused them to be favored by natural selection is
    removed). The small-beaked birds can again get enough to eat to be able to
    reproduce, and so their population increases. In other words, the
    population of the large-beaked birds increases relative to the population
    of the small-beaked birds when conditions favor large beaks, and it doesn't
    when those conditions no longer exist. That seems to me to be a pretty
    good example of natural selection resulting in descent with modification
    (evolution).

    Did I correctly understand the point you were trying to make or did I miss
    something?

    John



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