Human and ape phylogeny

John grehan jgrehan at TPBMAIL.NET
Sun Apr 6 10:27:01 CDT 2003


At 03:55 AM 4/5/2003 +0000, Ken Kinman wrote:

>      As for the orangutan-human data you have presented to some "pro-chimp"
>systematists, it would be interesting to see how such data would hold up
>presented to a wider audience (such as TAXACOM as a whole).

I thought I did earlier, but evidently I did not. I will re-post tomorrow.
I may at some point post the human chimp/African ape characters with
commentary. In that respect I find it interesting that for some papers
there are a wealth of human-African ape synapomorphies, but very few by
comparison for either human-chimp or human-gorilla. The chimp-human
connection seems to be substantiated in large part (from morphology) by
nesting within the human-African ape node rather than by its own merits.
The list of human-orangutan characters does not have this situation.

An additional point of interest (please note that I say of 'interest'
rather than any necessary significance) are some comments emerging that the
early hominids (such as australopithicenes and Orrorin) are not looking as
chimp like as expected for such a short interval from the presumed
chimp-human split. Some australopithicene skulls, however, do have a rather
orangutan-like profile (see Extinct Humans by Tattersall and Schwartz).

>     And as for having investigated soft-tissue characters outside of the
>great apes, the paper you cited DID analyze these characters with respect to
>the lesser apes (Hylobates) as an outgroup.

Perhaps this is the case. It was not apparent to me by the way that they
appeared to indicate that they rooted the tree after the characters were
denoted. Several characters had a more derived state in the outgroup and
yet they were still included.

>And I would reiterate that there is no strong reason to expect that a more
>distant outgroup (Old World
>monkeys) would change the results (although as I stated before, one never
>knows).

The results may change if a character absent in the gibbon (implying a
derived state within the remaining ape taxa) was widespread or throughout a
more distant outgroup. A case in point is the shared presence of thick
dental enamel in the human and orangutan. The generally primitive state is
thin enamel found in chimps, gorilla, gibbons, and all other primates
except for one Old World and one New World monkey. One may decide that the
human-orangutan situation represents a synapomorphy for their relationship
independent of the monkeys, or it is just a primitive retention lost in all
the other taxa. My preference is for the former - but it is just a
preference. Of course the chimp model would also suggest that thick enamel
comes and goes all over the place (although so far the thick enamel pattern
appears to be correlated with other features such as the presence of a
single palatine foramen in fossil and living taxa).

>      If so, perhaps the potential misrooting of molluscs might be a better
>choice for your attempt to show science as a process in action.

The human-ape connection is a better choice from my point of view due to
(a) my own interest and (b) greater public recognition of the taxa involved
(no one has to have an explanation of what a chimp is for example).

>We shallsee.  If the orangutan-human hypothesis really has some strong
>support, I
>would be the first to admit it, and change sides in the debate.  But I still
>haven't seen anything convincing up to this point.

I would not expect anyone on this list being convinced of anything based
upon a scattering of postings. It took me quite a bit of reading to be
'convinced' that there was something in the orangutan hypothesis and even
now I hold my breath on it.

John Grehan

>       ------- Cheers,
>                   Ken Kinman
>*****************************************
>>From: John grehan <jgrehan at TPBMAIL.NET>
>>Reply-To: John grehan <jgrehan at TPBMAIL.NET>
>>To: TAXACOM at USOBI.ORG
>>Subject: Human and ape phylogeny
>>Date: Fri, 4 Apr 2003 19:21:07 -03-30
>>
>>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
>
>
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