Tim Tyler  wrote:

> John Wilkins  wrote or quoted:
> > Tim Tyler  wrote:
....
> > > New siblings are often forced into competition with their parents -
> > > resulting in "divergent selection".
> > 
> > And none of this seems to me to have any connection with the idea that
> > species have a "life cycle" or "duration"
programmed into their
> > structure.
> 
> It does suggest that young species are systematically different from old
> species.  However, it leaves open the question of whether the reasons for
> those differences arising are "programmed into their structure".

The only way in which new species can be *systematically* different -
that is, different for all new species - is that they must have no more
variation in their gene pool than their parental form, and most likely
less (since they are a sampling of the parental species), until they
have had time to accrue mutations. However, they will have differing
amounts of viable recombination to see them through. If that is not
enough, they will go extinct under conditions that require more
variation than they presently have.

Diverging selection occurs only when the new species are in symaptry
with their ancestral species. Since the majority of species most likely
form in allopatry, whatever causes them to diverge cannot be due to
competitive selection, and so it is probably either drift, or a
side-effect of selection for local conditions. In either case, it is not
selection itself.

Sympatric speciation is now on the board again, and in that case the
very *fact* of speciation is due to (individual) selection. Again, this
is not deep. There is no "program" here - just the process of sympatric
selection. On individual varieties within species.
> 
> > > Species senescence, species infant mortality, and systematically
> > > different selection pressures on young species - isn't this all
> > > indicative of the existence of developmental cycles in species?
> > 
> > It would be if they were real effects or processes.
> 
> Which it seems highly plausible that they are - at least in the
> case of divergent selection and high species infant mortality.

Neither of which strike me as species-level properties or processes.
> 
> Of course there are more difficulties than normal in establishing
> the existence of such effects empirically - due to the difficulties
> in identifying most branching events.
> 
> However a fairly cursory look at (e.g.) our own family tree shows
> a number of what appear to be very young infant deaths (e.g. the 
> Neanderthals).
> 
> IMO, there's more than enough information out there to establish
> high species infant mortality as a real phenomenon.

The infant mortality here is of individuals. Neandertals had a long
duration (one exceeding that of our own species to date, I recall) as a
species.
> 
> > > What grounds are there to assert that there are no species 
> > > developmental cycles?
> > 
> > On the grounds that, unlike a multicellular organism that is neither
> > colonial nor a biofilm, species do not share mechanisms among their
> > members that go to directly form larger than organismic structures.
> 
> Cities?  Flocks?  ***Species***?

There is a city-causing developmental program in Homo sapiens (and not
an aggregate outcome of many individual activities)? The species has a
flocking algorithm or developmental pathway? As for species, what do you
mean? That a species has a species-forming program?
> 
> ISTM that species do exactly what you say they do not here.
> 
> > There is no *development* in a species, nor any credible mechanism for
> > it.
> 
> I see nothing incredible about the mechanism I described for
> high species infant mortality.  Most incipient species fail
> when their island (or lake) is invaded by descendants of their parent
> species, when it sinks into the ocean - or when a land bridge
> to it forms.
> 
> The existence of divergent selection on young species is equally
> uncontroversial.
> 
> It's possible to argue that different characters in youth and old age no
> more indicate a developmental program than the melting of a snowman 
> indicates it has one.  I wonder if that's your position on this issue.

I believe you are shifting ground between the properties of memebers of
a species, shared by perhaps all members (such as a reproductive
strategy or adaptation), and properties of the species as a whole. All
that a species (qua species) has as a property is the property of not
recombining when in sympatry with related species. All else is a
property of components.

This is why I mentioned the fallacies of composition and division
before. If a deer is fleet, to use Williams' famous example, that does
not mean the species of deer is fleet (in fact the species' range may
remain static for thousands of generations, ceteris paribus). If a
species increases its range rapidly (in geological terms) that does not
mean the individuals of that species move rapidly in geological terms
(each individual may be sessile and move no more than the rocks it sits
on). And so on.

Likewise, if physical forces sculpt the state of the species
(mountain-building dividing a range, or climatic change driving it to
revenant populations) these are not properties *of the species*, and so
they do not count as a lifecycle.
-- 
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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