[Taxacom] hominid evidence

[John Grehan]

Highly autapomorphic conditions have sometimes distracted systematists
(e.g. tarsius), but they are intrinsically uninformative about
relationships and are not a problem for phylogenetic analysis.

I am not sure that there is any evidence that our body plans are
modified for upright bipedal locomotion. We can certainly walk bipedally
as a preferred locomotion as a result of the body structure that we have
(plan is also teleological so I prefer not to use it).

I cannot comment on a 'shortage' of synapomorphies in general, but for
the human orangutan clade what is quite amazing is that there is almost
a super abundance, with 28 features well corroboraetd, and perhaps
another dozen that have yet to be properly investigated. I am tempted to
characterize the morphological evidence for the human-orangutan clade as
'extraordinary'.

We used parsimony analysis because that is what the chimpanzee
supporters have used. The only polytomies arose when comparing all
fossil taxa considered, and this was due to the large number of missing
characters in various fossils that were often known only from partial
fragments. And some more fragile features such as the incisive foramen
tend to break up before or during fossilization.

John Grehan

> -----Original Message-----
> From: Dr. David Campbell [mailto:amblema at bama.ua.edu]
> Sent: Wednesday, July 01, 2009 12:30 PM
> To: John Grehan
> Cc: taxacom at mailman.nhm.ku.edu
> Subject: RE: [Taxacom] hominid evidence
> 
> On the specific example of human-ape comparisons, a significant
> difficulty is that humans are morphologically highly apomorphic.  Our
> body plans are significantly modified for upright bipedal locomotion,
> whereas the apes retain a primarily climbing and knuckle-walking
> build.  Some help for this issue comes from a study of fossil
> hominids.  Exactly what to do with highly apomorphic taxa is a more
> general problem in phylogenetics, both in terms of the cladistic
> aversion to autapomorphies in classification and in terms of how to
> deal with a shortage of synapomorphies.
> 
> Conversely, having only a few characters also gives little resolution.
> In particular, parsimony produces soft polytomies when presented with
> either identical data or a set of similar taxa differing only
> autapomorphically.
> 
> --
> Dr. David Campbell
> 425 Scientific Collections Building
> Department of Biological Sciences
> Biodiversity and Systematics
> University of Alabama, Box 870345
> Tuscaloosa AL 35487-0345  USA