EKurtz wrote:
> "phillip smith"  wrote >
> 
> How can we know this. Presumably we can only know this when the individual
> 
>>is dead. As they may other wise have more offspring in the future. Also do
>>you count the fertile offspring if they all fail to reproduce even if 
>>though
>>are fertile. They may be fertile but have a mutated mate recognition 
>>system
>>or perhaps they breed  but the next generation dies.
>>Mutations like grandchild less
>>
>>http://www.ucalgary.ca/UofC/eduweb/virtualembryo/mago.html
>>
>>Would up set your case. If you parents produced offspring with the
>>grandchildless phenotype would be fertile but would have no grandchildren
> 
> 
> Looking at this issue from the point of view of an outsider, I get the 
> feeling that "fitness", which is essentially a statement
about probability 
> of survival (of something) over time, has been reified into an attribute of 
> an organism, similar to objective characteristics such as weight and color. 
> As a result, we are eternally immersed in pointless theological disputes 
> about its meaning and relevance.
> Consider the case of a sexual species into which a parthenogenic female is 
> introduced by mutation. Assuming that she and her immediate offspring 
> survive, and that the population size is constant, her offspring will 
> effectively displace the sexual type in a few dozen generations. But 
> ultimately the population will likely succumb to disease as a result of lack 
> of genetic diversity. So what is the "fitness" of the
mutation that caused 
> the transformation?  A meaningless question, in my view. The only thing that 
> matters is the probability at any time after the mutation is introduced that 
> its populational frequency has a given value. Without the introduction of 
> time and probability, no understanding of fitness is possible.
> When we say that a novel variation confers "fitness", we are
merely guessing 
> about its effect on the population in the near future.
> 
One thing that is stressed to students (and then, no doubt, subsequently 
forgotten) is that fitness is defined with respect to a particular 
environment.  Change the environment, change the fitness.  In that 
sense, it is a property of an individual: in environment X, individual Y 
will have fitness Z.

Of course, from an instrumentalist perspective, you're right that it's 
the frequency in a population that is ultimately important, but fitness 
is a major determinant of that.  Hence its importance.

Bob

-- 
Bob O'Hara
Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax:  +358-9-191 51400
WWW:  http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: www.jnr-eeb.org
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