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RE: Species & Giraffe necks

Noting first the determinations of species based on phenotypes
is not easy even for species having living representatives to
analyze and is often made on the basis of additional information
such as geographical distribution or behavior, Paleontology is 
severely crippled by the fact that most of the phenotype is
gone by the time you get it. This would imply that some amount
of doubt must enter even the most secure determination of 
species (even genus) in paleontology.

I have read, but do not know it to be true, that even specialists
cannot tell a lion from a tiger on the basis of the skeleton alone.
Can anyone comment on this?

G. Derkits

> ----------
> From:         smithjb@sas.upenn.edu[SMTP:smithjb@sas.upenn.edu]
> Reply To:     smithjb@sas.upenn.edu
> Sent:         Monday, April 12, 1999 11:29 AM
> To:   dinosaur@usc.edu
> Subject:      RE: Species & Giraffe necks
> Derkits, Gustav E, JR wrote:
> > 
> >     I'm glad to see someone on the professional side recognize the
> > undefinability of species. The Grants' work on finches shows the
> > problem in action - species can define and undefine themselves
> > by hybridization. 
> >     A mathematical note: If the definition of a species 
> > requires that a surface be drawn in either sequence space or 
> > design space that separates two species, then Turing's theorem 
> > and the Blum-Shub-Smale theorem on recursive systems both
> > show that "species" is, in general, undefinable. 
> >     That doesn't mean the concept isn't useful.
> > G. Derkits
>       I think a rather lot of us on the professional end of things feel 
> this way.  It is one area that is just as cloudy in neontology as in 
> paleontology.  However, it is acute in paleontology when the system 
> rewards the naming of new taxa.  I think this list is an excellent place 
> to cite examples of that process in effect...
> It is difficult to devote energy to it, but some of us are trying...
> -- 
> __________________________
> Josh Smith
> University of Pennsylvania
> Department of Earth and Environmental Science
> 471 Hayden Hall
> 240 South 33rd Street
> Philadelphia, PA  19104-6316
> (215) 898-5630 (Office)
> (215) 898-0964 (FAX)
> smithjb@sas.upenn.edu