Australopithecus and orangutans

[Ken Kinman]

Hi John,
     I must say that I do find the orangutan-human hypothesis more and more
intriguing, although I am still rather skeptical.
     The orientation of the zygomatic arch  reminds me (in a way) of the
struggle I have been having with the orientation of the shoulder joint in
coelurosaurian dinosaurs and birds, and whether such a character can ever be
used (in conjunction with others) to draw a more clear (abrupt) boundary
between dinosaurs and birds.
      I just wonder if more statistical analysis of such features will help
us or not (in either case).  Especially in the case of apes, I wonder what
factors (that we cannot yet understand) could affect the morphology of a
zygomatic arch-----its function in attracting the opposite sex (for example)
versus other functions that might be driving the orientation in the opposite
direction.  The most parsimonious answer in the end might elude us for years
or even decades, especially if it involves reversals of a reversal.
       And in the end it may very well depend on whose intuition is more
acute, even if it seems counter-intuitive in the early stages of debate.
But I guess that is the "grist that will feed the mills" of future
historians of science.   Will cladistics ever reach a stage where intuition
in character selection is no longer a major factor in the success of such
analyses?  Perhaps yes (eventually), but it will no doubt come
differentially in different taxa and at various taxonomic levels.  It's
really no easier to predict than in many other fields of human endeavor.
Hopefully it keeps us constantly alert without upsetting our equilibrium.
         ------- Cheers,
                    Ken Kinman
******************************************
>From: John Grehan <jgrehan at SCIENCEBUFF.ORG>
>Reply-To: John Grehan <jgrehan at SCIENCEBUFF.ORG>
>To: TAXACOM at USOBI.ORG
>Subject: Australopithecus and orangutans
>Date: Tue, 13 May 2003 12:01:32 -0400
>
>For those interested in the ongoing exploration of the orangutan hypothesis
>I recently found out that the lower zygomatic arch of the Australopithecus
>cheekbone is oriented the same way as the orangutan, and not the chimpanzee
>or gorilla, and not humans either for that matter. A forward facing lower
>zygomatic arch otherwise is well recognized as a synapomorphy for
>orangutans and their fossil relatives such as Sivapithecus. The arch of
>chimps and gorilla is mostly sideways facing.
>
>If one posited our evolution from an African ape the similarity of the arch
>between modern humans and African apes would be explained by common
>ancestry, but the Australopithicenes present something quite different. The
>alternative possibility is that Australopithecus is really an upright
>orangutan relative and its orangutan arch is secondarily lost in Humans as
>the facial skeleton was shorted so the resemblance to African apes is a
>superficial convergence.
>
>As an aside, the arm length of Australopithecus is much longer than it is
>often portrayed in artistic reconstructions where it appears to come down
>to the lower thigh as on humans. Its real reach appears to be at or lower
>than the knee. This is not necessarily pointing to orangutans more than
>other apes, but it shows a much different overall body structure to the
>popular form.
>
>John
>
>Dr. John Grehan
>Director of Science and Collections
>Buffalo Museum of Science
>1020 Humboldt Parkway
>Buffalo, New York 14211-1293
>Voice 716-896-5200 x372
>Fax 716-897-6723
>jgrehan at sciencebuff.org
>http://www.sciencebuff.org/biogeography/Panbiogeography/Panbiogeography-Gate.htm
>http://www.sciencebuff.org/HepialidaeGate.htm

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