Guy Hoelzer  wrote or quoted:
> > "Tim Tyler"  wrote in message

> >> I wrote an essay about group selection recently.
> >> It can be found at:
> >>   http://alife.co.uk/essays/reviving_group_selection/

[...]

> Stirring would seem to always result in mixing, but this is not the case.
> Stirring sometimes causes segregation and possibly even increased
> divergence.  For example, if you stir a well-mixed volume of sand with
> particles of varying size you will find that the larger particles become
> aggregated at the surface.  In a biological context, imagine that you have
> conditions favoring character displacement in parapatrically distributed
> subspecies.  Geographical stirring in this case will intensify the selection
> process and drive divergence, and perhaps speciation, faster.
> 
> My general point is simply that you can energize a system by stirring it,
> and the outcome will not necessarily be homogenization.

What a fine analogy ;-)

As an aside I notice that I have so-far failed to mention Guy in my essay.

I'm sorry about that.

I should perhaps add at this point that the elements of the essay that 
deal with "habitat-specific selection" basically consist of me presenting
ideas that I acquired primarily during past discussions with Guy Hoelzer.
-- 
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