Several questions on evolution, and mutation (rate)

Ram Samudrala ram at mbisgi.umd.edu
Fri Sep 6 20:04:06 EST 1996

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.  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.

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.

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

>From this and your other postings, and as Jim Foster pointed out, you
>seem to be trying to make the term "evolution" *synonymous* with
>"mutation", when mutation is simply one of the modes by which
>evolution occurs, as is natural selection,

Not at all, as demonstrated above.  Mutation is just one way for new
function to evolve.


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