Several questions on evolution, and mutation (rate)

Don Cates cates at cc.umanitoba.ca
Sat Sep 7 18:36:04 EST 1996


ram at mbisgi.umd.edu (Ram Samudrala) wrote:

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

[snip]

(Ram Samudrala)
>>> 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). 

(Doug Yanega)
>>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.

[snip]

Let's see if I understand what you mean.  I will give some examples and
my understanding of what your interpretation woiuld be.  Then I will
explain why I think you would be wrong. If I am wrong about your
interpretation I am sorry but it is an honest (possibly  flawed) reading
of your post.

There is some change in function of a gene. You call this evolution. It
is beneficial and spreads through the population by natural selection.
You call this natural selection. What if the individual who aquired this
new function failed to have offspring. According to you, evolution took
place but natural selection failed. I would think that the spread of the
innovation must take place before one can say that evolution took place.
What if the change was not beneficial, but neutral? Would you say that
evolution took place? For me, it's only evolution if the change gets
passed on to a new generation.
What if the change was lethal? A literal reading of your definition
would still call this evolution. I  don't *think* that you mean this. I
certainly don't know anyone who *would* call this evolution.
But then what of the beneficial or neutral change that fails to spread
because of chance? Do you call *this* 'evolution'. If so, I don't agree
and do not believe that many would agree. 
But if you agree that the change must be established in at least a small
population before it can be called evolution, what was the mechanism by
which this group aquired the change? Certainly not by the same mechanism
that created the change. So by my reconning, 'evolution' requires both
the change and the spread and your definition won't  do.


The best thing about mistakes is the joy they bring others.




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