                          GREAT MYTHS OF EVOLUTION #4
                                by David Menton

    IN  THE  FAMOUS  EXAMPLE  OF  THE  PEPPERED  MOTH,  WE CAN ACTUALLY SEE
    EVOLUTION IN ACTION

    The Peppered moth  (Biston  betularia)  is  typically  a  whitish  moth
    covered  with  black  spots.   This  coloration  provides  an effective
    camouflage for the moths as they rest on  certain  Birch  trees.   Like
    humans,  however,  these  moths can be found in a range of pigmentation
    from very black to very white and all shades in  between.   In  a  much
    touted  study  in  England  it  was found that when the white trees, on
    which the moths rested, became dark from  industrial  pollution,  birds
    ate  more of the lighter moths (apparently missing the darker ones). It
    came as no surprise that the population of darker moths increased while
    the lighter  ones  decreased.  It  was  further  observed  (but  rarely
    mentioned) that when cities cleaned up their air, the trees got lighter
    and  the  lighter  moths  again  predominated.  This is clearly natural
    selection in action but is this evolution?  Not really, unless we  call
    the  natural  variation  within  species  that occurs in all plants and
    animals "evolution".  The problem with equating this type of  variation
    with evolution is that it is STRICTLY LIMITED.  There are, for example,
    over  150 varieties (breeds) of dogs recognized by the AKC and more are
    added each year, but they are ALL DOGS  (Canis  familiaris).   You  can
    select  for  dogs with long ears or short ears, big dogs or small dogs,
    but you can,t select successfully for dogs with wings.  The  reason  is
    simple,  there  are  no  genes  for  wings (and their associated struc-
    tures) in the gene pool of the species  Canis  familiaris.   Thus  dogs
    remain  dogs and Peppered moths remain Peppered moths and, as far as we
    know, they always have and always will (excepting extinction).  One  of
    the  great  triumphs  of  modern genetics has been to explain how it is
    possible to have so much variation with in a species  with  out  losing
    the  distinctiveness of the species itself.  This is now known to be do
    to multiple alleles in the gene pool of the species.  For many genes of
    a species there exists several alternative  versions  (alleles)  though
    any  individual  can  have  no more than two "versions" of a particular
    gene at one time.  Thus a person may have eye color genes for blue eyes
    or brown eyes, but they are still eyes and both remain Homo sapiens. If
    we were all genetically alike we would be clones! An entire species  of
    identical  twins  would  not  be very interesting but more importantly,
    such a population might not survive long in a variable environment.  In
    conclusion, natural  selection  among  existing  alleles  is  known  to
    promote  the  stability  and continued survival of a species, but it is
    not known to be responsible for why we have come to have people,  cows,
    dogs, moths, giraffes etc. etc. etc.

                    FROM: M.A.C. Creation - Evolution PBBS.
                           (314) 821-1078    3/12/24


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