Date: Thu, 23 May 1996 18:24:30 -0600
Subject: Re: pigs could fly -Reply -Reply


Paul, Seilacher's work sounds interesting, but I wish you would tell
me how differential equations "explain" the range of molluscan shell
forms.  I don't know what that could mean.

And doesn't "function" include more than constraints?  Doesn't it
imply the accomplishment of certain tasks, i.e. life and reproduction
promoting tasks, solving the problems of food, shelter, predators,
mates, etc?

I'm happy to hear that Seilacher includes adaptation among
contributions to morphology.  Phylogeny and other constraints alone
are not likely to produce any evolutionary change at all.  Those
things work against any change, don't they?  And when some trait
seems to fit its circumstances, to solve a particular problem, then
it seems unlikely to be due to random change or sampling error.  And
since it has not existed for ever...

Nobody wants to be a vulgar "adaptationist", but I wouldn't want to
see the natural selection baby go out with the bathwater either.

To imagine some benefit to every trait of everything is silly, of
course.  I've seen some of that in "explanations" of societies and
cultural traits, usually in terms of benefitting the group of people
or the disembodied culture itself in some way.

Lisa


>>> Paul Gallagher <pcg-AT-panix.com>  5/23/96, 05:19pm >>>
Seilacher's "construction morphology" emphasizes how phylogeny,
function, and adaptation contribute to morphology: [snip]  For
example, many of the forms of molluscan shells have been 
explained as the result of various adaptations, but Raup (if I
remember right) showed how differential equations explain the narrow
range of forms the shells can take [snip]

In general, I'm inclined to think of macroevolution and population
genetics as separate issues.  The idea of species selection is one
possible way they are decoupled.  As a result, I'm inclined not to
attribute any evolutionary change to adaptation  without a lot of 
evidence.

Paul


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