Re: Dwarfism in Dinos

[JWagner@snlnet.com]

     I recently sent Dinogeorge a long and rather rambling account of why I 
     think Cope's Rule is not supported by evolutionary theory, and why it 
     is possible that dwarfism is a major component of evolution, and 
     indistinguishable from speciation.  I do not have the time to go into 
     it further, and I'd rather not forward the letter to the group, 
     although he is welcome to.  A brief summary goes like this:
     1)  Many of the factors which contribute to dwarfism are the same 
     factors which we believe are involved in speciation.
     2)  It is probable that, for various reasons which cladistic analysis 
     is intended to overcome, that the descendants of dwarves are not 
     always recognized as being related to the original, larger species.
     3)  It is possible that paedomorphosis (which I assume is often 
     involved in dwarfism), may "turn back the clock" on derived 
     characteristics, disguising the close relationship of a dwarf and it's 
     parent.
     4)  Any species which, at some stage in it's life, is a certain mass, 
     may evolve into a a new species of that mass, even if that mass is 
     considerably less than the mass of the parent species.
     
     The argument goes on, but that's the upshot.  Note that I have not 
     gone into the evolutionary pressures for dwarfism, I believe they 
     ought to be clear (niche partitioning was just mentioned, for 
     example).
     
     Jonathan. R. Wagner
     
     P.S.  Is it possible that, in common parlance, these "dwarf" species, 
     such as the mammoths, might be better termed "midgets (a midget being 
     a stunted, but proportional human, as opposed to a disproportionate 
     dwarf), while the dinosaurs mentioned, which have probably gone on in 
     evolution beyond being a miniature of another species, should be 
     considered proper "dwarves" of a larger phenotype?