Guy Hoelzer  wrote:

> in article c7778e$a1v$1{at}darwin.ediacara.org, John Wilkins at
> john_SPAM{at}wilkins.id.au wrote on 5/3/04 9:47 PM:
> 
> > Jim McGinn  wrote:
> > 
> [snip]
> 
> >> All traits are species selected traits.
> > 
> > Even those that are polytypic *within* the species?
> 
> Perhaps ESPECIALLY those traits that are polytypic *within* the species.  I
> think that it is fair to say that selection at one level tends to coordinate
> the interactions among the parts that constitute that level, including the
> specialization of diverse roles.  For example, selection at the level of the
> individual organism seems likely to have guided the proliferation of tissue,
> organ, and organ system diversity within individuals, and engineered
> functionally effective paths of interaction among these parts.  I would
> similarly expect selection at the species level to engineer within species
> polymorphism.
> 
> Guy

This is what I don't get about species selection theory. If we moved the
level of selection down to the organism, you have just said that
intrasomatic genetic variation is maintained by selection upon
organisms. In effect, you are claiming the equivalent or analogue of
maintenance of chimerism by selection. How can selection on species
cause the maintenance or evolution of intrapsecific variation, and why
should we prefer that account to the more likely and efficacious account
of selection and drift of individual traits at the organism level?

What selection on organisms does is not to maintain intraspecific
variation of *genes* except the production of immunological antibodies
(which are not preselected), and every cell in that body shares the same
genome, suitably expressed or repressed, at some point in the
proliferation and potentiation of itself or its precursors.

This overall developmental cycle is maintained by selection on organisms
according to the properties of these traits. But there is nothing
analogous in species selection. There are no developmental cycles in a
species. Population structure is largely contingent - there is no
mechanism for dividing demes, or structuring them, or modifying that
structure, apart from individual selection and drift, or in short
ordinary population genetics.

So how is the downward arrow of causation applicable in this case? In a
homeostatic system like an organism, the state of the system can affect
the satte of the parts, but species are barely if at all homeostatic,
gene flow accounts (which apply at the individual level)
notwithstanding.

I would appreciate your views on this Guy. Larry Moran has tried to
explain it to me, but I just don't "get" it. And I am afraid I find
Gould's views incoherent.
-- 
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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