"EKurtz"  wrote:-


> EK:-
> 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.

JE:-
This is the case for Neo Darwinian fitness
but it is *NOT* the case for Darwinian fitness.

Most agree that fitness is a reproductive
value, i.e. some sort of reproductive maximand.
The idea that fitness is just organism survival 
which was made popular by Herbert Spencer's "the 
survival of the fittest", can easily be refuted.

Gene centric thinking employs the term "survival" 
to now mean the phylogenetic survival of independent 
genes, i.e. genetic replication does not mean anymore,
the reproduction of genes. Survival has been
redefined to mean the "survival" of genes over 
many organism generations. This redefinition
just creates multi levels of mass confusion
because it deletes critical epistatic gene 
fitness information.


Darwinian fitness: 
This concept can be exactly defined, 
measured and tested to refutation because it's
a single level of fitness. The definition is: 
the total number of fertile forms reproduced 
by each parent into one population. This fitness 
constitutes a finite reproductive total per competing
selectee, per population. These must all be compared to 
each other by simple default. Here the largest 
total fitness is naturally selected for. At the 
gene level Darwinian fitness constitutes one epistatic 
fitness. 


Neo Darwinian fitness: 
This concept cannot be exactly defined,
measured and therefore tested to refutation because
it is too complex, i.e. involves multi levels 
of fitness the theory of which is _not_ understood. 
I have  attempted to make sense of it using the logic 
of nested sets. It just decays into a single level: the 
largest nested set. This is because all nested 
sets are selected as just the one, largest nested set. 
All that can be done with Neo Darwinian fitness 
multi levels is provide a so called  "expected 
fitness". Here you tend to get what you expect ;-)
 

> EK;-
> 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?

JE:-
The fact that "everything changes" in biological
nature is balanced by "most things stay the same".
The key to understanding fitness is understanding
how nature can provide stability with constant 
change. Most of this has to do with gene
fitness epistasis (multiplicative gene fitness
associations producing highly geared phenotypes,
via canalisation and assimilation). 

In your example asexual selection 
removes the 50% reproductive cost of sex at
a cost: reduced diversity. Selection
balances these two conflicting requirements
by selecting the parent that reproduces the
largest total of fertile forms within one
population. Even complex strategies that vary
between sexual and asexual reproduction can be 
selected for via a single Darwinian fitness 
maximand.

> EK:-
> 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. 

JE:-
The populational frequency of a mutated
gene is entirely dependent on the number
of fertile forms that have it unless you
are only referring to genes "in vitro". 
In turn, this depends on the total 
number of fertile forms reproduced by each 
parent within the one population in which
each parent must fitness compete because
infertile forms have zero fitness because
their genes are trapped. The
total fitness of each parent is a Darwinian 
maximand. It cannot be selected to be reduced. 
If it could be then a parent can be naturally 
selected to produce its own extinction. Such 
a supposed act is just biologically absurd.

> EK:-
> 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.

JE:-
The total fitness of a fertile form within one
population is not just a probability. Here,
no guesses are involved. The Darwinian view
provides an objective and testable to refutation
view of fitness but the gene centric Neo Darwinian
view only provides guesses of what it expects
and guess what, it always gets what it expects
(dear oh dear)....




Regards,

John Edser
Independent Researcher

PO Box 266
Church Pt
NSW 2105
Australia

edser{at}tpg.com.au


John Edser
Independent Researcher

PO Box 266
Church Pt
NSW 2105
Australia

edser{at}tpg.com.au
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