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Re: Refs, please... was... Re: AAT Theory
Paul Crowley (Paul@crowleyp.demon.co.uk)
Fri, 27 Oct 95 00:39:00 GMT
In article <Pine.OSF.3.91.951024151159.1930B-100000@curly.cc.utexas.edu>
eohippus@curly.cc.utexas.edu "David Froehlich" writes:
> > > On Sun, 22 Oct 1995, Paul Crowley wrote:
> >
> > I'll probably have to call in Jim Moore, cos I don't think you'll
> > take it from me. But the only thing a change in environment can
> > force is the extinction of a local species.
> Lots snipped
>
> I still think we are talking past each other. By my reading of what you
> have said, adaptation is impossible. Extinction is not the only response
> to change, take a look at the finches in the Galapagos. It has been
> demonstrated that changes in beak size mirror changes in the
> environment. If you were correct then any change in the environment is
> likely to make an organism go extinct. This doesn't happen.
When the Galapagos environment changed (i.e. new volcanic islands
emerged from the sea) some members of local individual species were
wiped out (i.e. some fish, etc.). They did not adapt. Some finches
got there and, very much in the long run, they adapted into a lot
of new species. They found a series of empty niches they could fill.
When the savannah/mosaic expanded to reduce the forest, the forest
species suffered. They did *not* adapt in consequence. To assert
that they did, or might have, is the "evolution forces" error. If
they were going to adapt they would have done it already. Adaption
happens; it is just never "forced". A species starts to exploit a
new environment, then maybe becomes a sub-species and then maybe a
full new species. An environment change *may* open up a new niche
which was not there before - but you have to say how. The
savannah/mosaic theory does not suggest any new niche. The AAT is
also a bit weak here too. Specifying the new (and empty) niche is
the vital bit.
Paul.
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