Text 94, 183 rader
Skriven 2004-09-18 16:52:00 av John Edser (1:278/230)
Ärende: Testing Evolution Via Gen
=================================




Tim Tyler <tim@tt1lock.org> wrote:

> > > > I have described an experiment that can eliminate all
> > > > natural selection within an _expanding_ population 
> > > > only allowing genetic drift as causative to allele
> > > > freq. changes. All you have to do is artificially
> > > > force all members of one population to raise the
> > > > exactly the same number of fertile forms to adulthood
> > > > where this number is larger than just a parental
> > > > replacement value.  The prediction is: all natural 
> > > > selection must be halted within this experiment while 
> > > > Darwinian fitness equality can remain enforced. Thus only 
> > > > genetic drift (which cannot be eliminated) is now left 
> > > > to cause "evolution".

> > > TT:-
> > > It won't work: 
> > > Organisms with fatal or severely deleterious mutations will
> > > still be selected against - as will organisms who don't
> > > manage to produce any fertile offspring - despite the
> > > best efforts of the managers of the experiment.

> > JE:-
> > I agree that eventually selection must end the
> > experiment for the reason you describe. I did
> > mention that eventually this would happen.
> > However, this fact underscores rather then 
> > undermines what I am suggesting. My main point 
> > was that my definition of Darwinian fitness can
> > suspend Darwinian natural selection for 
> > enough time to allow a test of random
> > drift as evolution within an expanding
> > population. [...]

> TT:_ 
> You could certainly magnify the effects of drift. 
> A small population size helps with that as well.

JE:-
If the species has a high fecundity
(can reproduce a large number of immature
forms via each reproductive act) then drift
will be even greater.

An experimental test is _required_ for the Neo 
Darwinian assertion that drift can produce evolution
without selection. Only this experiment provides
such a test.

> > > TT:-
> > > You can't eliminate selection - all you can do is
> > > change the selection criteria.

> > JE:-
> > I am arguing you can suspend Darwinian
> > natural selection for a considerable period
> > within a natural population allowing a test
> > to refutation of the my definition of
> > Darwinian fitness.

> TT:-
> In practice, you'd have a *very* hard time dealing with any
> severely deleterious mutations that popped up.  You would
> likely find you had a few sickly individuals on your hands -
> and making them have 2.4 kids (or whatever) would be challenging -
> and so fitness equality would not be preserved.
> This would most likely happen immediately - not after
> a long wait for drift-induced genetic rot to set in.

JE:-
I don't think that "this would most likely happen immediately"
because of genetic canalisation. C.H. Waddington's experiments
of over 50 years ago did indicate (using fruit flies) that the 
effects of most mutations are canalised, i.e. a more or less standard
phenotype is still produced. The opposing effect, assimilation, allows
for a non standard phenotype via just a small/no mutation.

> > > > JE:-
> > > > The population will deteriorate to such an
> > > > extent that it will become impossible to enforce
> > > > Darwinian fitness equality and Darwinian selection
> > > > will force its way into that population to
> > > > correct the dissolution caused by drift acting
> > > > alone.

> > > TT:-
> > > Yes - that sounds about right
> > > In practice, you can't eliminate selection.

> > JE:-
> > You can, for a finite period of time.
> > This is enough to test to refutation
> > my definition of Darwinian fitness.
> > Also, I argue, it will be enough to
> > refute the evolution by drift hypothesis
> > which entirely dominates evolutionary theory 
> > turning it into an irrefutable iron man
> > theory on a par with creationism.

> TT:_
> It sounds as though we all agree that drift has specific
> effects on the population.  

JE:-
I entirely disagree with the Neo 
Darwinian classification of these 
effects. Neo Darwinians classify drift 
effects as "evolution" but I classify them 
as _strictly_: random variation". Since nobody
is suggesting that variation alone can evolve
man and an ape from a common ancestor
then it does not matter if any form
of variation can or cannot be tested
to refutation. What is being suggested
is that man and ape can evolve
from a common ancestor via the Darwinian
process of evolution by natural selection
where random processes like sampling error
only constitute either random or non random 
variation. It does not matter to the Darwinian
argument if what is defined as variation 
can or cannot be refuted but it matters
enormously if selection cannot be refuted 
simply because selection and not variation is 
the defined cause within the Darwinian argument. 
Since drift is ubiquitous and cannot be eliminated
for any significant period of time but selection 
can be, arguing that drift alone can cause evolution 
reduces the theory of evolution to just a non testable
"iron man" theory on par with creationism.

> TT:-
> It acts to cause undirected -
> and most likely in the long term deleterious - changes in
> the population.

JE:-
Therefore, I  see no _rational_ argument that
can allow drift, which can only "cause undirected -
and most likely in the long term deleterious - 
changes in the population" to cause evolution, yet
this remains the Neo Darwinistic position in 2004.

> TT:-
> This seems to be much the same position as those arguing
> that genetic drift causes significant changes in natural
> populations, though.  How would observing the effects of
> genetic drift (by magnifying it) refute their position?

JE:-
No, my Darwinian position and the Neo Darwinistic
position remain opposed because Neo Darwinians
continue to argue that drift without selection can cause
evolutionary change whereas I argue Darwinism
insists that it cannot. Only the Darwinian argument
meets a minimal Popperian standard (provides a
point of refutation) because only Darwinian selection
and not Neo Darwinian genetic drift can be halted
for any _significant_ period of time via the experiment
provided.

Regards,

John Edser
Independent Researcher

PO Box 266
Church Pt
NSW 2105
Australia

edser@tpg.com.au
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