On Tue, 27 Jan 2004 06:40:25 +0000 (UTC), 
John Edser  wrote:
> phillip smith wrote:

[snip]

> The question is. Is the definition of evolution as changes in 
> gene frequencies  reasonable. I have no question that the 
> frequency of phenotypic traits can change under selection. 
> This not the same thing.

We need a way to *define* evolution so that we know it when we
see it and so that we can distinguish evolution from other
things that superficially resemble it.

Evolution is a phenomenon of populations and not of individuals
so any *definition* has to address populations. Evolution deals 
with changes in heritable characteristics (genes/alleles). Simple
changes in phenotype due to environment, for example, are not 
examples of evolution. (The classic examples is increased height
and health of Caucasians over the past 500 years.)

When a population evolves the genetic composition changes. Hence,
the basic minimum definition of evolution is a change in the
frequency of alleles in a population over time. Nobody has ever
come up with a better definition that allows us to separate
evolution from similar phenomena and to recognize real evolution
when we observe it.

> JE:-
> Yes, they "are not the same thing."
> Causation is the basis of reasoning
> within the sciences. Deleting causation
> within the sciences is like deleting all
> musical instruments within music. At the
> moment it remains unclear if a gene freq
> change is a cause of evolution or just an
> affect of another cause. Four epistemologically
> different causations can exist here:
> 
> 1) A gene freq change causes Evolution.
> 
> 2) Evolution causes a gene freq change.
> 
> 3) An unknown causes both.
> 
> 4) No causation exists between them,
> i.e. they are correlated  but
> independent, events.

As usual, John gets confused by his own rhetoric. The *definition*
of evolution says absolutely nothing about cause, nor should it.
We now know something about the cause of evolution (natural selection,
random genetic drift, etc..) and those explanations form the core
of evolutionary theory. It would be wrong and silly to *define* 
evolution in terms of one of its causes. We don't do this for other
phenomena in science (e.g. gravity, chemical reaction, earthquake,
etc.) so why should we do it with the word "evolution."




Larry Moran
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