Perplexed in Peoria  wrote or quoted:
> "Tim Tyler"  wrote in message
news:cfg2sf$nco$1{at}darwin.ediacara.org...

> > In my essay I suggest three factors that have been rather neglected
> > by group selection's critics that may assist group selection's operation:
> >
> > * Habitat-specific selection;
> > * Xenophobia;
> > * Divergent selection;
> >
> > http://alife.co.uk/essays/reviving_group_selection/
> 
> And I continue to doubt that any of these things has anything to do with
> group selection, pro-or-con.  Group selection and spatial variation resulting
> from viscosity and individual selection are completely different things.
> Variation between groups caused by individual selection does not provide
> any kind of raw material for the operation of group selection - at least if
> you accept G. C. Williams' "parsimony" principle.

In case I have not made this abundantly clear in the past (in my 
discussions with John Wilkins) I most certainly do not accept
G.C. Williams "parsimony" principle.

I assume this is a reference to the bit in "Adaptation and Natural 
Selection" where Williams gives the examples of a deer outrunning a bear.

Williams says a slow herd of deer will become extinct, while faster ones
will survive.

He distinguishes between an adaptive herd of deer and a herd of 
adaptive deer - and that this is thus an example of individual
selection - and not group selection - on the grounds that in
science one generally prefers explanations on the lowest possible
level.

I disagree completely.  Group selection is (or at least should be!)
differential reproductive success of groups on the basis of group 
traits.  Consititing of fleet deer /is/ a trait of a herd of deer.

It is also clearly a heritable trait - groups of fleet deer will tend
to give rise to other groups of fleet deer when they divide into other 
groups.

Therefore this qualifies as an example of differential reproductive 
success of groups on the basis of group traits - and thus of group
selection.

Parsimony is an irrelevance.  Nobody has to choose between group
selection and individual selection in the first place.  If (in a 
particular case) the two theories happen to be the same theory
(i.e. they make all the same predictions), then that represents good 
grounds for *not* choosing between them - and instead regarding them
as equivalent descriptions of exactly the same phenomenon.

I note that (in practice) the two theories will normally /not/
be exactly equivalent.  A population being divided into groups
will normally affect who breeds with whom - and will introduce 
quantisaton effects involving inbreeding and difficulty in finding
mates if the group sizes ever become small.

Last time the whole subject came up I gave the example of planets
being attracted to the sun by gravity.

Nobody claims planets are not /really/ attracted to the sun by gravity - 
and that what is /really/ going on is that individual atoms are being 
attracted to each other; that nobody should speak of gravitational 
attraction between planets and their star - since lower-level explanations 
are preferred in science, and the parsimony priniciple dictates that it 
is not /really/ planets and suns that are attracted to one another,
but rather their individual atoms.

If someone /were/ to argue that planets were not /really/ attracted to
the sun by gravity - due to the parsimony principle - everyone would think 
that they were talking confusing nonsense - and the criticism would be 
spot on.
-- 
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 |im |yler  http://timtyler.org/  tim{at}tt1lock.org  Remove lock to reply.
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