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Defining evolution
Ronald Kephart (rkephart@OSPREY.UNF.EDU)
Tue, 12 Mar 1996 14:07:58 -0500
In message <26031107511399@vms2.macc.wisc.edu> Andrew Petto writes:
"I would argue that evolution requires speciation-- not progress, not hierarchy,
not direction. But these speciation events bring into being new biological (and
behavioral) structures and functions that form a foundation for new ways of life
-- thus, "higher" or perhaps I should say "more inclusive" taxa, taxa that
include variations on a major organizational theme."
With all due respect, and after consulting my physical anthropologist colleague,
I have to stand by my original definition: evolution is change in gene
frequencies. The change may or may not lead to speciation, and may or may not
be the result of patterned, non-random forces such as natural or sexual
selection. There are some who argue that most evolution is non-patterned, the
result of random mutations taking hold in a population even tho they carry no
selective benefit.
One classic example of evolution without speciation is the sickle-cell trait,
the gene frequencies of which vary thru time depending on the prevalence of
malaria. Without malaria, the frequency is very low because all persons with
the gene are at a disadvantage compared to those without it. Enter malaria, and
persons with one copy of the gene are at an advantage over both non-carriers and
carriers of two copies. Take away malaria, and non-carriers regain their
original advantage. This is evolution, even tho no new species appear.
And by the way: my response to the Florida Times-Union's editorial support of
the Tenn legislation has not yet appeared, altho two letters in agreement have!!
I'll keep y'all posted.
Ronald Kephart
Dept of Language & Literature
University of North Florida
Jacksonville, FL USA 32224-2645
Phone: (904) 646-2580
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