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Re: body size ad nauseum



In a message dated 98-05-15 08:17:55 EDT, cadams@hh.gpz.org writes:

<< Why did hadrosaurs and ceratopsians evolve from smaller dinosaurs?  There
 were big sauropods around in the Cretaceous.  Why didn't they evolve into
 other herbivorous dinosaurs?  Because large size slows down evolution,
 while at the same time making you vulnerable to extinction.  For the same
 reason, elephants are never likely to evolve into anything dramatically
 different.  But mice?  Just give them a few million years. >>

Just so. I noted this back in Mesozoic Meanderings #2 first printing (1991),
but I'm sure this is commonly known among evolutionary theorists. Smaller
animals tend to be more fecund and to have much smaller territories than
larger animals, both tendencies leading to increased species diversity in the
smaller animals. Increased species diversity in turn begets a faster
evolutionary rate, since there are more distinct populations within which
mutations can become established.