> > For example, the issue of the unit of selection is
> > under debate (although it doesn't seem to be as public or
> > ego-driven).
>
> I'm not convinced that there is a single "unit of
> selection". There is a *minimum* unit of selection, the
> gene. But depending on the circumstances, multiple genes, an
> organism or a population can a ct as a "unit of selection".
That's the debate--gene-unit backers say that more complex
organizations *don't* act as units of selection--they only
influence the true units: the genes. Or at least that's
what I understand.
> > ["non neo-Darwinian mechanisms"]
> >
> > [stasis]
> > [habitat tracking]
> > [drift]
> >
> > Again, this seems like a particular slant on the theory to
> > exclude these.
>
> Yes, the neo-Darwinian slant - as opposed to the Punctuated
> Equilibria (PE) slant.
OK. I fear we've perhaps only added to the confusion about these
terms. My understanding is that people with a selectionist slant
and with a non-selectionist slant (and all kinds of hybrid
pluralist slants) all fall into 'neo-Darwinism', although they
argue about details. That is, the research project as a whole is
"neo-Darwinism" and there are various groups within that umbrella.
> > For one thing, selection may be just as
> > much responsible for stasis and habitat tracking as it
> > is for speciations.
>
> If the scalar rate of genetic variation is relatively
> constant over time (as observation and experiment appears to
> strongly indicate), it can only be selection that keeps the
> population as a whole in phenotypic stasis.
Correct. That's what I was trying to point to--since selection
is responsible for statis and for speciation (along with other
mechanisms), it seems to me that it is necessary to include
statis and tracking with speciation as a 'neo-Darwinian process'.
> The point I was making is that, while stasis certainly
> affects the process of evolution, I see stasis as something
> that occurs under the appropriate environmental
> circumstances *instead* of evolution, rather than being a
> mechanism of evolution. Again, this issue may be more
> semantics than substance.
I think its more substantial--it is an interesting question
where, how, and why populations remain in stasis vs. speciate.
This discussion is hard to carry out if you don't include
stasis as part of the vocabulary. It is a discussion that seems
well-placed inside the neo-Darwinist program, and one that is
interesting and important in figuring out the importance of,
for instance, the rate of ecological change as related to
speciations.
> To clarify my understanding: neo-Darwinian processes only
> cause evolution (change in the relative frequency of alleles
> in a population) under the appropriate environmental
> circumstances; under other circumstances the same processes
> inhibit evolution.
Right, but I'd say that the whole field of processes and
mechanisms of evolution, whether caused or inhibited, is one
that neo-Darwinism is interested in exploring.
[selectionists uninterested in drift, tracking]
> Probably for the same reasons that "aimless wandering" and
> "running on the spot" are unlikely to ever make big bucks as
> spectator sports. :-)
LOL! I'll have to remember that.
> > "Selectionism vs. pluralism"
> > is the way self-described 'pluralists' refer to this
> > particular
> > debate. I'm not sure what would rule them out as
> > neo-Darwinists,
> > though.
>
> My reading of the debate, as it has been documented in the
> popular science works of Dawkins, Gould and Eldredge, is
> that it is frequently the proponents of PE that distance
> *themselves* from the "gene-centric" and "selection-centric"
> claims of neo-Darwinism. I have little difficulty
> understanding the observations emphasised by proponents of
> PE as a reasonable outcome of neo-Dawinian processes.
That's my understanding of the argument, too, but, as you
point out, it seems (at least to us), that PE theories (and
neutralism, and drift, and so forth) are within the neo-Darwinian
program.
> The other point is that much of the "neo-Darwinian vs.PE"
> controversy is generated by creationists who hope thereby to
> discredit evolutionary theory. This is curious, because they
> generally cry "foul" when I use "Christianity vs. Judaism
> vs. Islam" to discredit theism.
You think? That isn't my impression. I think the NYRB articles,
the various books, articles, and so forth come from a genuine
disagreement between selectionist forces and non-selectionist
forces. While it seems to me that both are "neo-Darwinist"
(indeed, that what makes the debate as strong as it is--both
sides care about the same program and their roles in it), they
definitely have differing ideas about where that program should
be headed. My understanding is that, while some Creationists
may recycle this argument into the tired, old 'evolutionary-theory-
is-almost-dead' cry that's been around for decades, they haven't
done anything to help or hinder the argument.
-Greg