Human and ape phylogeny

[John Grehan]

Here's a question for all the cladistic experts on this list. I admit to
having a relatively superficial expertise with cladistics so I want to
measure my current perceptions against any responses on this list. My
question concerns the 'cladistic' quality of an article cited on this list
as increasing the support for a human-chimp/african ape clade vs human
orangutan by S. Gibbs, M. Collard, and B. Wood (2002) Soft-tissue anatomy
of the extant hominids: a review and phylogenetic analysis. Journal of
Anatomy 200: 3-49.

At first glance the paper seemed very impressive. The authors utilized 171
characters and a cladistic analysis. The number of taxa was limited to
humans and extant apes only which did make me wonder if some of their
characters might not qualify as synapomorphies with further comparison
including at least the old world monkeys. Then I read that "No a priori
judgements were made as to the primitive or derived condition of
characters". My reading of that statement is that the characters were not
'cladistic' in the sense of each standing as proposed synapomorphies.
Instead they were phenetic.

The authors then state that "Hylobates was assumed to be the basal hominoid
genus and the cladograms were rooted accordingly". Since the characters
were not defined as synapomorphies with respect to an outgroup, making one
of the taxa the basal lineage seems to be an externally imposed criterion
rather than being generated from the characters themselves. With this root
the characters were subject to 'cladistic' analysis.

Am I correct to view this paper as a 'cladistic' analysis of phenetic
characters with an arbitrary rooting of one of the taxa being analyzed. If
I am then this paper hardly seems to me to stand up as a reliable support
for the human-chimp clade. I am getting old and perhaps my understanding of
cladistics based on what I read by Hennig, Nelson where cladistics was all
about the analysis of proposed synaomorphies is now out of date and I
missed the boat where cladistics is now all about the analysis of phenetic
characters.

John

Dr. John Grehan
Director of Science and Collections
Buffalo Museum of Science
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