Human and ape phylogeny

[John grehan]

My thanks for the various feedback.

My use of phenetic characters referred only to those characters that are
not separated out into apomorphic and plesiomorphic states. Phenetic in my
direct experience was never used to refer to phenotype. The term
fphenotypic was used for that. But others obviously have a different
experience.

I seem to have some agreement that where in individual characters are not
selected for analysis on the basis of their being already hypothesized
apomorphies then the characters are phenetic. Some seem to indicate that if
these phenetic characters are subjected to 'cladistic' analysis techniques,
then the analysis is cladistic in these sense even though the characters
are not. This seems to be the case for molecular phylogenies that are
'cladistic' renditions of non-cladistic characters. In morphology the
question is to what degree various characters used in cladistic analysis
are themselves cladistic in being hypothesized apomorphies.

When it comes to human-ape affinities there is no doubt that in terms of
overall similarity of characters (not distinguishing between apomorphic and
plesiomorphic states) humans have share the greatest similarity with chimps
and gorilla. The same applies to the sequence data and perhaps the
congruence of phenetic morphology and phenetic genetic sequences is not
surprising.

With respect to the conflicting sets of cladistic characters (orangutan vs
chimp) the situation appears to be one of conflicting views about either
the character itself (whether it stands up as a valid distinction), or
whether the character is truly cladistic (i.e. is in actual fact unique to
the taxa concerned). I have presented the orangutan data to a couple of the
pro-chimp systematists and so far the orangutan data have held up. The main
differences are either in one's personal opinion as to whether a character
is realistic, or whether it is correctly interpreted. In the converse there
appear to be some differences in whether many of the purported
human-African characters are confined to those taxa. For these arrangements
the strongest support has been for the human-chimp/gorilla node whereas the
number of synapomorphies for either chimp or gorilla are comparatively weak.

The paper on soft-tissue characters is problematic in that much of the
information is distilled over a huge range of literature involving sources
that are sometimes decades apart. Unless I missed something, the authors
have not directly verified many if not most of the characters - but I could
be wrong about that and will have to check. It is also uncertain to what
extent the characters were investigated outside the great apes. More
enquiries to be made.

As this issue continues to unfold I will likely make further postings. My
current feeling about this is that it might be premature to accept the
human-chimp as an unproblematic given just because a majority say it is so.

John Grehan