Guy Hoelzer  wrote in
news:c545ol$2v1u$1{at}darwin.ediacara.org: 

> in article c52l5k$2fr8$1{at}darwin.ediacara.org, William Morse at
> wdmorse{at}twcny.rr.com wrote on 4/7/04 9:41 PM:
> 
>> Guy Hoelzer  wrote in
>> news:c51ar3$20pm$1{at}darwin.ediacara.org:
>> 
>>> in article c501hh$1kai$1{at}darwin.ediacara.org, William Morse at
>>> wdmorse{at}twcny.rr.com wrote on 4/6/04 9:54 PM:

>> Bob also noted that heritable variation is necessary, but I believe
>> that the actual mechanisms involved in reproduction do make heritable
>> variation inevitable. To be more precise, the mechanisms guarantee
>> that variation exists and is heritable (let me just note that if this
>> were not true drift as we know it would not occur). Perhaps the
>> mechanisms don't _guarantee_ that the variation affects fitness. But
>> for the variation not to affect fitness would require the walking of
>> a "neutral tightrope" - variation could only affect
non-coding DNA,
>> amino acid sequences away from the binding site, etc. Obviously much
>> variation is in fact neutral, but certainly not all. So your argument
>> appears to be not that selection won't occur, but that it will not
>> result in evolution, because it will only diminish variation for
>> fitness. 
 
> No.  This is not my argument at all.  I do think that natural
> selection is a real process and that it is an important path to
> biological adaptation. However, I am trying to make the argument that
> drift happens continuously and always, selection happens only
> sporadically and under special conditions.  Fisher's fundamental
> theorem makes the point that selection is self-extinguishing even
> under the conditions that induce this process. 

And my point is that selection doesn't stop, it is only that under some 
(perhaps many) circumstances it  keeps selecting the same thing. That may 
mean that you will only _see_ it sporadically, but it doesn't mean it is 
not occurring. If you offer me a choice between a and b over and over, 
and I choose b over and over without fail, does that mean no choice is 
being made?

  
> Speaking of maximization, I don't follow your reasoning in asserting
> that there must exist a maximum fitness value if selection is to
> generically diminish heritable variation for fitness.  I don't think
> that Fisher made this assumption.
 
I may well be wrong, but my intuition is that if you have a range of 
values in a population (fitness) x1..xn, and you have a function 
(selection) about which the only thing you know is that it will increase 
the value, i.e. f(x) > x, you cannot state that the range f(x1).. f(xn) 
will be less than the range   x1..xn unless there is an upper bound on f
(xn). 


Yours,

Bill Morse
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