Australopithecus and orangutans

[John Grehan]

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