Re: The "fuel" of evolution

From: Anon. (bob.ohara_at_NOSPAM.helsinki.fi)
Date: 11/25/04 

Date: Thu, 25 Nov 2004 19:48:22 +0000 (UTC)

EKurtz wrote:
> "phillip smith" <deletethis-phills@ihug.co.nz> 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
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Relevant Pages

  • Re: Bet Hedging, Risk Aversion, Sex, and the Unit of Selection
    ... > behave as if they were risk averse maximizers of fitness (i.e. ... > On Population Growth in a Randomly Varying Environment ... > environment and other offspring adapted to different environments. ... An organism only HAS a few offspring. ...
    (sci.bio.evolution)
  • Re: Hamilton meets Matata
    ... >> that includes parental investment in offspring). ... >> animals having identical genomes and living in the same environment may ... > There's expected fitness at birth - which is not affected by having ... Kin selection in, for instance, insects, does not translate to kin selection ...
    (sci.bio.evolution)
  • Re: The "fuel" of evolution
    ... As they may other wise have more offspring in the future. ... > are fertile. ... So what is the "fitness" of the mutation that caused ...
    (sci.bio.evolution)
  • Re: Absolute or just relative fitness?
    ... > A measure of absolute fitness would be more acceptable to me. ... > 3) Darwinian fitness cannot be selected ... > Number of fertile offspring is not enough. ... How can you tell whether a particular offspring is ...
    (sci.bio.evolution)
  • Re: NS and AaD curves
    ... If the environment changes, so does ... >> passed on from a parent to an offspring. ... fitness is the expected odds of an offspring with a given gene ... a different sequence each time a finite series of "runs" transpires). ...
    (sci.bio.evolution)
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