"Tim Tyler"  wrote in message
news:cfql3m$129r$1{at}darwin.ediacara.org...
>
> [What does it mean to say that fitness increases in evolution]
>
> However - there *is* a sense in which progress could be painted as an
> increase in absolute fitness.
>
> To give a specific (if somewhat hypothetical) example:
>
> Recreate a number of historical time periods, millions of years apart.
>
> Take a sample (using some sort of random sampling process) of organsms
> from each time period - and test their survival in each of the other ones.
>
> The hypothesis that evoultion is progressive in character in the way
> I suggest would strongly suggest that the later organisms would exhibit
> better survival (over all the environments) than the earlier organisms
> would.
>
> Such an experiment avoids the criticism that fitness must be evaluated
> in the same environment before comparisons can be made - by evaluating
> each organism in each environment.
>
> I note that any such criticism isn't really valid in the first place:
> in fact it is quite acceptable to ask whether modern organisms/ecosystems
> exhibit better survival when transplanted into ancient environments than
> ancient organisms/ecosystems do after transplantation into modern ones.

I think that you have sketched the correct thought experiment.

Though I am not sure that it is best to take the samples millions of
years apart.  I suspect that this is something like defining Newtonian
velocity - you get the best results in the limit as the delta-t becomes
smaller.  A single generation is the best, or perhaps a small number
of generations if you wish to smooth fluctuations.

It may also be useful to break down into components the change of the
environment between the two time frames.  These environmental include:
- Physical environment
- Population count changes of other species
- Evolution (change in gene frequencies) of other species.
- Population count changes in our species.
- Evolution (change in gene frequencies) of our species:
  - as manifested socially and ecologically.
  - as manifested in epistatic genetic interactions when mating takes place.

Fisher's claim that fitness monotonically increases assumes that none
of the above environmental changes are occurring - which is extremely
unlikely for the first four items above, and self contradictory for the
evolution of conspecifics.  Nonetheless, a careful thought experiment
such as the one you sketched above can clarify the meaning of Fisher's
claim, and show that it is not purely meaningless hot air.
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