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Re: "Cope's Rule" Put to the Test



At 04:57 AM 1/23/97 -0500, George Olshevsky wrote:
>>What I'm saying is that a population of small animals will
>evolve from significantly larger animals only under some pretty exceptional
>circumstances, whereas such exceptional circumstances are not required for
>the evolution of larger animals from smaller ones.

Again I dispute this.  As Jonathan Wagner has pointed out, it won't fit
hummingbirds - in fact the majority of perching birds (Passeriformes),
generally accepted to be the most recently evolved (and certainly the most
diverse) bird lineage, are on the small side - certainly smaller than
Archaeopteryx and I suspect smaller than their ancestors somewhere down the
line.  There are many extremely tiny bony fishes that may well have evolved
from larger ancestors.  I suspect the same may be true for dendrobatid
frogs, microchiropteran bats, murid rodents, the smaller shrews, perhaps
the smaller possums, dwarf lemurs etc.  Dwarfism is not at all uncommon on
islands.  Is it necessarily true (I don't know) that the smaller gazelles,
duikers, dikdiks etc did not evolve from larger early bovids?  The living
hyraxes are also considerably smaller than fossil forms (etc).  Not all of
these may represent ancestor-descendant relationships but I think such
cases should be checked out before we subscribe to George's proposition.

>
>
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net