Excuse me for interrupting but you mention species...

Jim McGinn  wrote:

> Tim Tyler  wrote 
> 
> > > As far as I can see, there is nothing wrong with an
explanation that is
> > > "for the good of the species" (group, deme, etc.)
so long as it is not
> > > harmful to the individual. Individuals tend to compete with
conspecifics,
> > > and in the case of a fixed carrying capacity any trait that
benefits an
> > > individual will subtract from the fitness of the rest of the
population.
> > > But what if the trait increases the carrying capacity? In this case it
> > > will still benefit the individual, but it will also benefit
the species!
> > > In general such traits may face stiffer odds of spreading than traits
> > > that benefit just the individual, since the individual benefit is at
> > > first just a fraction of the overall benefit. But once established at
> > > even a relatively small frequency, they may survive better than traits
> > > that merely benefit the individual, since they reduce the
odds of loss by
> > > sampling error by increasing the population. 
> > 
> > This is all well put.  However at the moment species selection faces
> > the problem of not having any good examples of species-selected traits.
> 
> All traits are species selected traits.

Even those that are polytypic *within* the species?
> 
> > If trying to find evidence for species selection
> 
> How about the fact that species exist.  Is this not evidence?

Sand dunes exist - do they undergo selection? It is arguable that many
or even any species are the sorts of entities that are coherent enough
and reproduce in the right way to undergo selection.
> 
>  - to illustrate that
> > is isn't totally impotent as a force in nature - examples where
> > adaptations favour the species and the indiviual are not terribly
> > useful - since the simple hypothesis of individual selection
> 
> Individual selection is not a hypothesis.  Nor is it a force.  It's a
> perspective.

What does this mean? [I may agree if only it were clearer]
> 
>  only
> > explains their existence rather well - and quantitative arguments
> > in this area are harder to make convincingly.
> > 
> > It is cases where the trait is either neutral to the individual - or
> > slightly deleterious - that would represent the best evidence for
> > species selection.
> > 
> > This is why modern group selectionists have congregated around
> > phenomena such as programmed death.  Death looks as though it
> > offers little individual-level benefit - but arguments can
> > be made that it improves group-level dynamics - e.g. by
> > systematically removing organisms with high parasite loads
> > from the population and preventing them from infecting other,
> > unrelated members of the same population.
> > 
> > So far I'm not convinced that these folks have a case - but
> > in terms of getting some evidence for high level selection
> > goes, this is the right /sort/ of example.
> 
> I'd agree.  But I just think we need to be cognizant of the fact that
> the tendency of scientists to object to this notion of selection
> happening at levels of selection higher than the individual level of
> selection invariably hinge on conventions of semantics rather than the
> reality of the phenomena.  The classic mistake is that people think of
> levels of selection (or units of selection) as tangible phenomena when
> in actuality they are nothing but theoretical perspectives.  Natural
> selection doesn't happen at levels, on levels, or to levels.  It
> happens to biological phenomena.  And a change in biological phenomena
> at one level of selection (or unit of selection) also represents a
> simultaneous change in biological phenomena at all levels (or units of
> selection).
>
Selection does not occur on anything; it only occurs on reproducible
traits (acc. to Lewontin) or on replicated entities (acc. to
Hull-Dawkins). Not every case in which sorting occurs is even remotely
like selection, and to simply say that anything that is biased sampling
in biology is selection overlooks both the uniqueness of selection as an
explanation, and the individually interesting features of other dynamics
(such as drift and canalisation).
-- 
Dr John S. Wilkins, www.wilkins.id.au
"I never meet anyone who is not perplexed what to do with their
 children" --Charles Darwin to Syms Covington, February 22, 1857
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