Several questions on evolution, and mutation (rate)

Doug Yanega dyanega at denr1.igis.uiuc.edu
Sat Sep 7 13:28:47 EST 1996


In article <50qhm6$tj2 at hecate.umd.edu>, me at ram.org wrote:

> Doug Yanega (dyanega at denr1.igis.uiuc.edu) wrote:
> 
> >pleiotropy are very important. The terminology "to observe new function
> >evolve" is a sloppy use of the word "evolve". What you APPEAR to mean is
> >"to observe the origin of a new function" whereas the more literal
> >interpretation is that you're talking about the *spread* of the new
> >function throughout the population. Both events - the origin of a new
> >trait (frequency from zero to non-zero) and its spread (low to high
> >frequency) are parts of the evolutionary process, but the phenomena
> >controlling them are different. 
> 
> Yes.  And I'm attempting to differentiate the two.  The spread of new
> function throughout the population is by natural selection. 

NO! Please think this through - this is EXACTLY why your use of the terms
is unacceptable. The change in gene frquencies across the population can
be accomplished by gene flow, drift, *OR* natural selection. You are
overlooking sveral important evolutionary phenomena. That is why the
overall process is called evolution, not the very narrow subset (i.e.,
only mutation) that YOU are attempting to restrict the term to.

> The
> origin of a new trait, which could happen over generations, is what I
> refer to as evolution.  In the Origin of Species book by Darwin, he is
> careful to make this distinction (though he doesn't refer to the
> latter as evolution), if I recall right.

He calls it mutation, as most people do.

> As I said, I think that the whole thing together (origin of new
> traits, and their selection) is commonly referred to as evolution.  I
> find this confuses the issues at hand.

Calling a tusk an elephant is a lot more confusing, in my opinion.

> >No, no, no. In BOTH cases resistance has evolved. In one case it evolved
> >from zero to non-zero frequency VIA MUTATION, in the other it evolved from
> >a very low frequency to very high VIA NATURAL SELECTION. 
> 
> Well, it's one use of the word.  I'd call the entire process, of a new
> trait arising from zero to non-zero frequency (via mutation,
> crossovers, magic, whatever) as evolution of that trait.  I'd call the
> spread of it through the population natural selection (if that was the
> mechanism of the spread). 

I have several texts on evolutionary genetics, not ONE does not call the
latter process evolution. Natural selection is a *subset* of the possible
modes of evolution.

> There are other papers in the literature
> which I believe make this sort of distinction. 

I'd certainly like to see ONE paper that says that natural selection and
drift are not modes of evolution, and that ONLY mutation is. Produce
*one*, please.

> Still, it's simply a
> matter of making sure the difference between the two is clear (and
> your language above is clear as well).  The point I am trying to make
> is that going from zero to non-zero frequency is not well understood
> (how do you even observe this?), whereas going from very low to very
> high frequency by means of natural selection is fairly well understood
> (I've observed this in the lab).

Then all you have to do is specify that you're talking about the origin of
new genes, but trying to redefine the word evolution to refer only to
those phenomena is not going to sit well with folks like myself who study
evolution and have to communicate clearly about it.

Sincerely,

Doug Yanega     (dyanega at mail.inhs.uiuc.edu)
Illinois Natural History Survey, 607 E. Peabody Dr. 
Champaign, IL 61820  USA  (217) 244-6817 fax:(217) 333-4949
affiliate, University of Illinois Dept. of Entomology
  http://www.inhs.uiuc.edu:80/~dyanega/my_home.html
"There are some enterprises in which a careful disorderliness is
    the true method" - Herman Melville, Moby Dick



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