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Re: Thoughts on Systematics and IntraSpecific Variations -Reply

On the subject of characters & cladistics (and, incidently, of 
Australopithecenes), there is a new paper by Melanie McCollum in Science that 
would have knocked my socks off, had I been wearing any at the time.  She makes 
a pretty convincing case that all of the facial characters that have been used 
in cladistic analysis of the robust hominids are traceable to enlargement of 
the molars.  Given that single change, everything else falls into place as a 
matter of developmental necessity.  Thus (she concludes) the cladistic analysis 
proves nothing because the characters are not independent and the only real 
difference from the gracile form could quite easily have arisen independently 
any number of times.

Since our knowledge of dinosaur developmental biology is rudimentary to 
non-existent, this seems like a particularly easy trap to fall into.  In fact 
we invite error if we give equal statistical weight to, for example, multiple 
quantitative measures of the same bone or series of developmentally related (an 
admittedly fuzzy concept) bones.

  --Toby White