Several questions on evolution, and mutation (rate)

Ram Samudrala ram at mbisgi.umd.edu
Sun Sep 8 18:33:07 EST 1996


Doug Yanega (dyanega at denr1.igis.uiuc.edu) wrote:

>Natural selection is not a form of evolution? 

No.  Because natural selection does not explain how you can get from
zero frequency to low frequency.  This is what I call evolution.
Natural selection has nothing to do with origin of a new trait, which
I call evolution.  Call natural selection a form of evolution is
confusing and misleading.

>Evolution is a *process*, and it can take place through several
>different *mechanisms*.

Yes.

>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.

Yes to the origin of new function (i.e, the new function has
evolved).  How can you call, a protein that remains the same, that
simply increases its prescence in the population, evolution? What is
evolving?  The protein?  The protein has stopped changing---it's just
being spread through the population.

>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,

That's your definition, which I obviously disagree with.  You're wrong
when you claim I say evolution is a single phenomenon. It is ANY
phenomenon by which the frequency changes from zero to non-zero.  I
think you are mixing two separate issues (zero to non-zero, and low to
high, which occur via a different set of processes) which I have
always found confusing, misleading, and non-illuminating (which was my
original point).  I don't care what you call you it, personally,  as
long as this distinction is made (which you are making).  If you wish
to argue about definitions, fine.  But it's purely a pedantic issue
as far I'm concerned.

>> 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 doesn't answer my first question.  Are you still claiming Darwin
called the origin of a new trait mutation?  Here's a scenario: there's
a gene duplication, one of the genes becomes inactive (due to
mutations), one of the genes keeps mutating for a while, and finally
the protein it produces gains new function.  Would you call this
entire process "mutation"?  How about: a foreign piece of DNA is
incorporated into the chromosome, mutates, and the resulting protein
gains a new function.  Would you call this entire process "mutation"?
I think that's misleading too!  It's clearly a lot more than
mutation.

>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.

Not true again.  Evolution could be through magic, an act of god, or
mutation (which I don't view as generally as you do, anyways).   All I
am saying is that evolution is where a gene goes from zero frequency
to non-zero frequency.

>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".

I don't exclude everything else but mutation, and besides as I
illustrate above, you canhave a variety of mechanisms by which a gene
goes from zero to non-zero frequency.  I call all of this evolution.

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

It is called that by some people, but I think they are wrong,
confusing, and misleading.  Evolution is only the first part---you
want to generalise mutation so much that you hide the terms "gene
duplication", "crossover", etc., all into mutation.  This is as
misleading as calling something like natural selection evolution. The
point is that natural selection by itself doesn't change the nature
of the gene/protein being selected.  It spreads that SAME gene/protein
through the population.  Evolution is the origin of NEW genes/proteins.

>the terms that way is effectively a non-distinction.

I clearly disagree, as I say above, there is no change occuring during
natural selection in that gene (this is not necessarily true, but if
it does it's evolving and being natually selected at the same time).

--Ram

me at ram.org  ||  http://www.ram.org  ||  http://www.twisted-helices.com/th
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