Jim Menegay  wrote:

> Tim Tyler  wrote :
> 
> > I hope the fact that several people are raising objections will draw
> > John's attention to the fact that his terminology - involving species
> > properties not being inherited - is counter-intuitive; and is not part of
> > conventional or orthodox usage of the term "species".
> 
> As one of the people who has "chimed in", let me dissociate myself
> from the bandwagon that you seem to think is forming.  I agree with
> John that for "species-level selection" to be accepted as a causal
> explanation of anything, there have to be "heritable"
"species-level
> traits" that natural selection examines in its sorting operations.

At least *one* person agrees then. Whew...
> 
> To my mind, a species-level trait must be "emergent" in some sense.
> In this, I seem to clearly be in disagreement with Tim.  My disagreement
> with John seems to be more subtle.  He seems to wish to use the
> word "emergent" a little more strictly than me, and he may also be
> more dubious than I am that emergent traits exist, however one defines
> "emergent".  He also seems to want to assign some traits that I would
> call species-level traits to lower levels, i.e. groups or populations.
> I think that he will come around when he realizes that these traits
> are not heritable at the lower levels due to gene flow, whereas they
> are (or can be) heritable at the species level.

If that could be demonstrated, I suppose so. I am not denying the
theoretical possibility of species selection. Instead I am saying that
what people usually mean by that is not, in fact, *species* selection. A
greater part of the time it seems to be a fallacious attribution to
species of properties and processes very much within the species.
> 
> "Heritable" is another word that deserves some explanation.  Part of
> the concept of heritability at the individual level is that the 
> genome of an individual does not change (except for rare mutations)
> as the individual matures.  Similarly, the concept of heritability
> at the species level also has to include the immutability of the
> species "genetic elements" during the species lifetime.  The only
> difference is that since species are potentially immortal, the limit
> on the mutation rate for calling a trait "heritable" can no longer
> be stated in terms of the number of mutations per generation.  You
> need to use the number of mutations per million years, or something.

I don't quite get this. So far as I can tell, there *are* no "genetic
elements" of species (but of course there are of traits, and organisms).
> 
> And, finally, we come to the "sorting" itself.  Again, an analogy
> with individual-level selection may be helpful.  Fisher's notion of
> "reproductive value" gives a sense in which the fitness of an
> individual changes over its lifetime - growing as it survives infant
> mortality and then falling as it approaches senescence.  I think that
> we can also define a species fitness that changes over time.  But,
> instead of a life cycle, species seem to have much less predictable
> ups and downs.  A "down", to my mind, is a drop in population.  That
> is, I am suggesting that the count of individuals in a species is a
> good measure of its success.  So, I am not so insistent that species
> sorting be distinguished from individual sorting as some people might
> be.  The difference between species-level selection and 
> individual-level selection resides in the traits that Nature examines
> rather than in the sorting that takes place as a result.

Sorting is sorting no matter what it happens upon. Selection, though, is
a very special kind of sorting, one that relies crucially on the
transmission of hereditable traits that correlate with economic success.
A fall in population size would not necessarily correlate with a
lowering of reproductive value (a term I *much* prefer over "fitness")
if in so doing it actually *increased* the RV of whatever it is that is
hereditable.
-- 
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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