progressive evolution

Richard M Kliman rkliman at ruacad.ac.runet.edu
Fri Jun 16 15:07:29 EST 1995


In article <Pine.SUN.3.91.950614115747.25439H at castor.cc.umanitoba.ca> gordonr at cc.UManitoba.CA (Richard Gordon) writes:
>Is natural selection sufficient to explain progressive evolution, or is 
>there something about the structure of the genome that enables the latter?
>
>-Dick Gordon, U.Manitoba[Jun14,95]

What, precisesly, is meant by the term "progressive" evolution?  Is this 
the same thing as "adaptation," or is it something else?  Adaptation 
resulting from the action of natural selection on heritable variation 
need not be progressive.  The fitness of an individual is a function of 
its environment.  Natural selection can increase the frequencies of certain 
alleles, perhaps raising them to 100%.  This population could be doomed 
if the environment changes.  In fact, wasn't this one of the early 
arguments against Darwinian evolution: that it did not guarantee 
progressive evolution to some "higher" organism (e.g., humans)?

Perhaps an analogy to Darwinian evolution would be a radio with 
quartz-lock tuning that seeks the nearest station on the dial that "comes 
in" over a certain threshold level.  It doesn't guarantee that you'll 
progress up the dial, or down the dial, but it should do a pretty good 
job of finding *something* to listen to (unless there's just nothing out 
there).

Rich Kliman
Dept. of Biology
Radford University



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