Re: What is the concept of fitness ?

In article <mo-dnWBXO944LeXVnZ2dnUVZ_ofinZ2d@xxxxxxx>, Cj <Cj@xxxxxxxx>
wrote:

John Wilkins wrote:
William Morse <wdNOSPAmorse@xxxxxxxxxxxxxxxx> wrote:

John Wilkins wrote:
William Morse <wdNOSPAmorse@xxxxxxxxxxxxxxxx> wrote:

Both these examples would let one gauge a fitness by a metric that is
true by definition, albeit limited to the domain involved - animals that
need to overcome fluid friction in the first case, terrestrial animals
that are toxic in the second.

Which gives room for selectionist explanations that do not rely on an
instantaneous rate of reproduction (the usual definition of fitness) but
instead rely on a selection matrix, as it were: given conditions a, b,
and c, we can expect that an increase in d will increase fitness, at
least if that increase can be achieved at a reasonable cost.
Expectation of a rate of increase *is* instantaneous increase (because
fitness can change if the environment does), and all you have done is
make the epistemology dependent upon some set of knowledge based on the
past. Sure, if you have the priors to make the rate of expectation
reasonable, then you can say fitness is what will happen in the future
(this is called the propensity conception of fitness), but right now all
you have is the instantaneous rate of increase as is or will be
observed.
While I normally advocate snippage, we might have lost something in
translation on this one.

I think snippage is the least of our problems. There's my brain to take
into account too...
Working with what is left, your response has me confused. My follow did
not discuss an expectation of a rate of increase, only of a direction of
increase. And fitness is not normally discussed as a rate, only as an
increase. We would have to take the second derivative to get a rate of
increase, and I have not seen this discussed in the literature,
although your use of it probably means that some of your references are
discussing a rate concept.

Not necessarily. The rate of increase notion is mine own (which I will
one day publish when I care enough). If an allele increases over time,
the fitness is the rate at the time in a given environment at which it
increases its frequency in the population. If the environment is stable,
then the rate will remain constant (well, actually as it approaches
equilibrium or fixation, then it will slow, but that's a matter of
derivatives anyway).

But what I was talking about above is what we can know about such rates.
We cannot *know* what the propensity is at a time t, only after t. So to
define fitness as what will happen in the future is a mistake. We only
*know* what happened in the past, and we are projecting that knowledge.
Furthermore, the set of knowledge I am using may be based in the past,
but that is irrelevant to the argument unless you think that the physics
of viscosity or the chemistry of toxicity is likely to change in the
future That was my point - that while fitness changes if the
environment does, certain aspects of the environment (e.g. the viscosity
of fluids) are fixed. I think this does lead to an expectation (not a
rate of expectation) as to characteristics that will be conserved or
enhanced in future organisms.

But fitness is not absolute to the (in this case, liquid) environment.
It is a matter of comparative rate of increase (or comparative increase
if you dislike the rate definition) of that allele *with all other
alleles in the population* or deme. So while the Reynolds number may not
change, the ways in which competitors get around or employ it will,
changing the fitnesses of *all* alleles relative to that "problem".


The liquid concept is interesting but what changes if the liquid is
non-Newtonian? e.g. ketchup?.
Cj

*
.....or blood, another non-Newtonian fluid.

earle
*

.

Relevant Pages

  • 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 ... rather the maximization of the expectation of the logarithm of ... An organism only HAS a few offspring. ...
    (sci.bio.evolution)
  • Re: What is the concept of fitness ?
    ... need to overcome fluid friction in the first case, terrestrial animals ... and c, we can expect that an increase in d will increase fitness, at ... the fitness is the rate at the time in a given environment at which it ... ....or blood, another non-Newtonian fluid. ...
    (talk.origins)
  • Re: Felsenstein and reproductive excess
    ... >conspecifics constitutes a deterioration in the environment for you. ... >model which would allow fitness to "increase" over time without population ... we have to distinguish between mutations that make an individual ...
    (sci.bio.evolution)
  • Re: DNA carries information
    ... The Fitness Value of Information ... on a detail (DNA), it took me some time to develop a coherent ... the germ of a distinction between significant ... tasting, making any measurement on the environment, nothing at all ...
    (talk.origins)
  • Re: Heritability of fitness
    ... >> the rate at which information 'about the environment' is accumulated ... >> in the genome and the heritability of total fitness. ... >> should be very close to zero. ...
    (sci.bio.evolution)
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