I am resending this as it appears to not have been posted

in article cnjpem$2jco$1{at}darwin.ediacara.org, Perplexed in Peoria at
jimmenegay{at}sbcglobal.net wrote on 19/11/04 4:31 PM:

> 
> "phillip smith"  wrote in message
> news:cniip7$2676$1{at}darwin.ediacara.org...
>> in article cnhhln$1rrr$1{at}darwin.ediacara.org, Perplexed in Peoria at
>> jimmenegay{at}sbcglobal.net wrote on 18/11/04 8:06 PM:
>> 
>>> We all know that heritable variation in characters affecting fitness
>>> is a prerequisite for natural selection.  Metaphorically speaking,
>>> we can even say that heritable variation is the "driving
force"
>>> for NS.
>>> 
>>> This is a good metaphor because variation plays a force-like role.
>>> Assuming you quantify "variation" as the variance in
fitness, the
>>> infamous "Fisher's Fundamental Theorem" assures us that the
>>> magnitude of the response is proportional to the magnitude of the
>>> "force".  Furthermore - (correct me if I am wrong here!) - the
>>> direction of the response matches the direction of the
"force".
>>> If the total variance in fitness is divided among several
>>> characters, the characters that evolve fastest are those that make
>>> the largest contribution to the fitness variance.
>> 
>> I think you may be in error here. Standard darwinism is not directed by
>> variation, assuming variation is every direction. Heritable variation in
>> characters does not force evolution. The rate of evolution is proportional
>> to variation. The force is the strength of selection. You could have very
>> high variation and no change at all in under intense stabilising selection.
> 
> I may well be in error, but your response suggests that I was simply not
> precise enough.  My claim is (ie. was meant to be) that the total
"force"
> is the total variance in fitness attributable to heritable variation in
> characters, with the various orthogonal components of that total being the
> heritable variation in fitness due to each character.

It appears I misunderstood you. Server me right for reading to quickly. It
seems you are talking about the variance in the contribution of a character
to fitness rater than variation in the character. So are you talking about
phenotypic plasticity or error in natural selections ability to select. What
I and perhaps JE took this as was genetic variation. If there is no genetic
variation then selection has nothing to operate on where as if there is not
selection the population should just diffuse out from the mean.
> My understanding -
> again, please correct me - if that under stabilizing selection the variation
> in fitness due to a character is simply not heritable.
> 
> I do notice one difference between a real force vector and a variance
> "vector", which is that the variance components are always
positive.  The
> response vector, on the other hand, is truly vector-like.  That may be
> enough to destroy the metaphor.
> 
>> However Kimura and Ohta had other ideas. If you take evolution as the change
>> in gene frequecies then the rate of evolution is a function of the mutation
>> rate ie variation if accept the neutral theory.
> 
> Oh, I do subscribe to the neutral theory.  Again I was probably insufficiently
> precise.  If I said that my "force" was driving
"evolution", then I was wrong.
> I should have said that the "force" drives
"adaptation" or drives "natural
> selection".
> 
>> It is a bit like diffusion vs mass flow.
> 
> You lost me here!  Is Fisher like diffusion and Kimura like mass flow, or
> vise versa?
Lost myself as well;-)
>> 
>> Snip
>>> Of course, the true value of a metaphor lies in the follow-up
>>> questions that it suggests.  Is there a difference in the fuel
>>> efficiency of various evolutionary situations?  Does the combustion
>>> require two different fuel components (oxidizer and reductant)
>>> with either component potentially limiting?  Etc.
>>> 
>>> 
>> I think a trap you may be falling into here is believing that fitness is a
>> real property of individuals. Fitness can only be ascribed to alleles.
> 
> Actually, I'm pretty sure I was claiming that total fitness is modeled as
> a property of types, with the components of fitness being modeled as
> properties of alleles.
> 
>> We can measure the frequency of an allele at time x and x +1 and
see a change
>> frequencies and try and determine the probability the change happening by
>> chance. If chance seems unlikely then maybe it was selection.
>> Fitness is a very slippery concept ...
> 
> Gee.  I didn't realize that.  John and I seem to have no trouble understanding
> each other re "fitness".  ;-)
> 

I should have said I am working on a replacement for fitness( see reply to
JE). I think fitness has fatal errors. We keep using it because we have had
no choice. Not that I am sure I an do better.
>> ... and I personally feel it has been badly
>> formulated. I am working on an alternative formulation that I feel is
>> superior but requires a rethink of population genetics. Unfortunately I need
>> to publish first in scientific journals for all the reasons that have been
>> recently discussed so I can not reveal it to sbe. This has been the fruit of
>> some ten years work. I need to finish the phd I should have finished eight
>> years ago. I have recently returned to a lab part time about 8 hours a week
>> when I am not  working. So I hope to finish this soon. I look forward to
>> presenting my ideas to sbe at the appropriate time.
> 
> Sounds interesting.  I look forward to it.
> 
>
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