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Re: "Random selection": an oxymoron.



In a message dated 1/24/99 3:13:07 PM EST, jbois@umd5.umd.edu writes:

<< Of the roughly 10,000 bird species, most 
 are small and are staying that way.  Why? Because, as Collias says, being
 small and flying allows them to conceal their nests.  This is a valuable
 rule.>>

This "rule" can apply only to certain small birds. It has no applicability
outside this narrow set of organisms. It is like calling the statement
"nearsighted people wear glasses to see better" a "rule." Besides, tomorrow
someone else will come up with a different reason that some bird species
remain small. Then what will happen to this so-called "rule"?

 << Well, let's see what happens if we relax the predation pressure by
 putting a small species on a predator-less island.  Pressure keeping them
 small disappears making other selection processes more important.  Another
 rule says: Due to Size/Metabolism economy of scale, it pays species to be
 bigger (until pathologies of size or some other competing force kicks in).
 These rules (and I am really not saying they are true--but they do deserve
 attention to figure out if they are true) are much more useful and
 predictable than the simplistic: Species grow bigger. >>

What you are calling "rules" are not rules, if there is a different "rule" for
practically every different species. There is no generalization, if every
"rule" is specific. We try to look for general rules, but the "rules" that you
are displaying are limited in their applicability practically to the species
for which they are created. They are not rules but characteristics of species,
like "blue feathers" or "jugal expanded." There is no point to creating a
welter of thousands of different rules whose applicability is so limited. You
are just adding to the chaos.

Cope's "rule" doesn't say "species grow bigger." It only notes a tendency.
There are lots of reasons that species can grow bigger, there are lots of
reasons species can stay the same size, there as lots of reasons species can
grow smaller. None of these reasons amounts to a rule. There are no such rules
in evolution; everything is contingent.