"Guy Hoelzer"  wrote in message
news:c9389m$e25$1{at}darwin.ediacara.org...
> in article c92cvt$3s4$1{at}darwin.ediacara.org, John Wilkins at
> john_SPAM{at}wilkins.id.au wrote on 5/26/04 8:26 AM:
> > I have already delivered myself of my dismissal of emergence as a
> > metaphysically interesting feature of physical systems, so I won't
> > rehearse it here. Flocking behavior, though, is a property of individual
> > birds (or boids) and their genetic and developmental programs, not of
> > flocks...
>
> I'm afraid that I don't understand your objection to my example.  I agree
> that flocking behavior is a property of individual birds, and not of
flocks.
> Similarly, flocks are a property of a species, not of individual birds.
> Therefore, a single genetic mutation can lead to heritability of flocking
> behavior at the individual level, and flocks at the species level; so
> changes in the frequency of this mutation can potentially be influenced by
> selection at both the individual and species levels.  Do you agree?

I have already delivered myself of my middle-ground position
between Guy and John, but, what the hell, I will repeat it here.

If a deme of swallows does well because it flocks, then the
individual swallows also do well.  If the flocking behavior
is due to individuals heading toward concentrations of
other birds sighted visually, then individual selection
seems to be the explanation of choice.

If a deme of peacocks does poorly because runaway sexual
selection has caused the males to carry outlandish tails,
then the individual peacocks also do poorly.  But an
individual peacock has no opportunity to do well in this
situation.  If it doesn't grow a tail, it can't reproduce.
If it does grow a tail, it cannot survive predation.  The
tail is a deme-level property, and deme-level selection
is the explanation of choice.

Notice that this is just the opposite of what intuition
would say about where the property resides.  A flock
seems to be collective, whereas a tail seems to be
individual.  Ignore the guidance of intuition!  Instead,
pay attention to whether an individual can do better
than the deme as a whole by bucking the system.  If
he can, then blame the individuals.  If not, then
blame the system.

Another example:  If the swallows flock because of sound
signals emitted expressly for the purpose of attracting
birds to the flock, then we have a borderline case.
An individual has no particular reason to signal, if
it lives in a deme of birds that ignore the signal.

Whenever you see frequency-dependent selection at the
individual level, there is the possibility that the
trait is maintained by feedback loops at the demic
level, and demic-level selection may be the best
explanation for what is happening.
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