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Several questions on evolution, and mutation (rate)

Doug Yanega dyanega at denr1.igis.uiuc.edu
Sun Sep 8 16:06:00 EST 1996


To try to finish this off...

In article <50t6e8$7lj at hecate.umd.edu>, me at ram.org wrote:

> Doug Yanega (dyanega at denr1.igis.uiuc.edu) wrote:
> 
> >> 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. 
> 
> That is correct.  As I said later in the post, I'd call it natural
> selection provided that was the mechanism.  If it was genetic drift,
> I'd call it genetic drift.  If it was magic, I'd call it magic.  But I
> would not call it evolution.

Natural selection is not a form of evolution? This view is not accepted by
evolutionary biologists. Evolution is a *process*, and it can take place
through several different *mechanisms*. You have been choosing ONE of
these mechanisms (the origin of new alleles) and calling *it* alone
evolution, thus implying that anything else - including natural selection
- is not evolution. That is precisely what I mean about calling a tusk an
elephant. Evolution is not *a* single phenomenon. It is ANY phenomenon by
which the frequency of alleles in apopulation changes between generations,
which means there are several different things which are "evolution", and
natural selection is one of these.

> >He calls it mutation, as most people do.
> 
> He calls the origin of a new trait mutation?  What happens if it
> didn't arise by mutation?

I would love to hear another way for a new allele to arise that does not
involve mutation. That is what one calls a change in the genome, after
all, and no new trait can arise without a change in the genome. Moreover,
a *trait* can be a feature at a higher level than a single allele.

>I don't believe we're
> communicating. 

Obviously.

> The spread of a gene through the population (low to
> high frequency) is what I call natural selection (IF IT HAPPENS BY THAT
> MECHANISM).  Evolution is simply the arising of the new function,
> whether it's through mutation or an act of god. 

Evolution is not simply the origin of a new function - in fact, it has
nothing necessarily to do with function whatsoever - merely ANY changes in
allelic frequencies over time, whether or not their function changes. You
CAN have different alleles with identical functions, and evolution can
still occur.

> >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.
> 
> Are you saying (in your first sentence) all these texts call natural
> selection "evolution"?  

Yes, they all consider natural selection to be one of the modes by which
allelic frequencies change over time, as well as mutation, and drift.

>I believe there is literature
> that calls origin of new function through mutation as evolution, and
> the spread of a gene through the population natural selection.  BUT,
> before you repeat your objection, I have NEVER SAID that it's "only",

Immediately above, you state EXPLICITLY that you do not call natural
selection a form of evolution, nor drift. In fact, you seem to refuse to
acknowledge that there *are* any _forms_ of evolution. Meaning the ONLY
phenomenon you consider to be evolution is mutation, from what I can see.

> Huh?  I don't see how you can get "only" from my posts, without
> overinterpreting what I wrote. 

Why do I feel like I'm in a Monty Python sketch? You said yourself above "But I
would not call it evolution." If you *exclude* everything else but
mutation, that IS the same as saying "only mutation".

>My "system" is a gene
> duplication with the two genes performing identical function, 

a gene duplication is a mutation...so far so good...

>one of
> the genes becoming inactive after acquiring mutations, then later
> gaining a new function (all of which I call evolution of the new
> function),

and this new function requires mutation as well - if nothing changes in
the genome, I can't imagine how any new function can spring into being -
still fine...

> and then this new gene is naturally selected for since it
> confers a selective advantage).  

Right - the point you seem unwilling to admit is that the *entire* process
is called evolution, NOT just the first phase.

> I believe it's important to make the sort of distinction I do, but in
> any case, the important thing is simply to make this distinction.

The distinction you are making is between mutation and selection, and as
long as you state it that way, there is no disagreement. But I know of no
definitions of evolution that would allow you to say "the first part of
this process is evolution, the second part is natural selection". That's
like saying "I will travel the first 50 miles of my trip in a motorized
vehicle, but the following 50 miles in a Chevy Belair". A Chevy Belair
*is* a type of motorized vehicle. The distinction you are drawing by using
the terms that way is effectively a non-distinction.

I'm leaving town tomorrow, and may not be back for a few months. I think
I've gone far enough with this.
Peace,

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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