Several questions on evolution, and mutation (rate)

Ram Samudrala ram at mbisgi.umd.edu
Sat Sep 7 20:10:32 EST 1996


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.

>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?

>> 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.

I agree, but that's not what I am doing.  I don't believe we're
communicating.  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.  All my examples of
evolution and spread of a gene have involved mutation and natural
selection, which I believe is where the source of confusion is.  But
they are just examples.

>> 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.

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

>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.

This is not been my claim at any point.  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",
and in both these cases, the mechanisms are the right ones.  I will try
to find this when I go into CARB, but when I publish my paper on this
topic (if I do), it'll be sure to have this distinction. 

>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.

Huh?  I don't see how you can get "only" from my posts, without
overinterpreting what I wrote.  The reason you seem to say "only" is
because I use mutation and natural selection, but that's the only
mechanism in my system.  I submit that there could be other
mechamisms, but for now they're irrelevant.  My "system" is a gene
duplication with the two genes performing identical function, 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 then this new gene is naturally selected for since it
confers a selective advantage).  

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.
When you say you study evolution, you don't say whether you study the
origin of new function, or its spread, or both.  Most people only
study the spread.

--Ram

me at ram.org  ||  http://www.ram.org  ||  http://www.twisted-helices.com/th
   TOTAL CRIMIMALIZATION was the greatest idea of its time and was vastly 
popular except with those people who didn't want to be crooks or outlaws.
     So, of course, they had to be TRICKED INTO IT... which is one of the
 reasons why MUSIC was eventually made ILLEGAL.            ---Frank Zappa



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