Re: Holloway's question

7 Aug 1995 15:09:35 GMT

alex duncan ( wrote:
: In article
: <> Ralph L
: Holloway, writes:

: >A question for Alex and Harry: What happens when you confine your
: >cladistic analyses for Siva, Pongo, Giganto, etc., to purely mandibular
: >characters? Isolated teeth and mandibles are ALL that is known to exist
: >for Giganto.

: That is what I've been encouraging Harry to do.

Done. See separate report.

: While the data base is
: impressive, it does include characters that in general are not used in
: cladistic analysis, as well as characters that are unknown in
: Gigantopithecus. I've already posted about the second category. In the
: first category are features such as body size (too difficult to determine
: polarity, and obviously a very labile character), geographic and temporal
: position,

Geography is turned off. Temporal position is handled as a stratigraphic
variable, with a low weight. These two factors do need to be addressed.

: diet (can we really KNOW this for a fossil species, or are we
: extrapolating from dental and masticatory anatomy, in which case the data
: should already been in there?).

Extrapolating from detailed dental/masticatory anatomy. In most cases, I
used the author's summary assessment.

: Until good cranial material was discovered for Ouranopithecus, it was
: often included in a clade with the sivapithecines, and was even placed in
: the same genus (I think) by Simons & Pilbeam (1967?). The mandibles and
: mandibular dentition are very similar to Siva, and I think many of the
: other character states were assumed to be similar or identical to those
: seen in Siva & Pongo.

I've seen authors disagree specifically on the valuation of O. character
states based specifically on the same remains (references at home). The
differences of opinion seem to revolve around allometry.

: A similar state of affairs exists today for Gigantopithecus. I suspect
: that the evidence for Giganto belonging to the Siva/Pongo clade is better
: than it was for Ouranopithecus. Kelley suggests that S. parvada is a
: reasonable precursor for Gigantopithecus. But, given the general
: similarity of the mandibles of the thick-enamelled hominoids, is it
: really outrageous to suggest that Giganto might have evolved from
: Ouranopithecus? I don't think that is the case, but if we begin our
: exercise by assuming Giganto IS a member of the Siva/Pongo clade, and go
: ahead and put characters in the database that are unknown -- but are
: similar to what we see in Siva/Pongo -- then we'll never prove anything
: about Giganto other than what we already "know."

I experimentally moved Gig. to the base of the clade, so that it could
access Ouranopithecus as well. It popped back up. I'm in the middle of a
thorough scrub of the database...

Harry Erwin
Home Page: (try a couple of times)
PhD student in comp neurosci: "Glitches happen" & "Meaning is emotional"