Human-orangutan phylogeny

[John Grehan]

At 06:00 PM 4/10/2003 +0000, Ken Kinman wrote:

>     Anyway, I heard from Gary Schwartz about the thick enamel supposedly
>shared by humans and orangutans, and they develop it by two different
>development pathways, so it is almost certainly a convergent character.

Here is what J. Schwartz (2001) had to say on molar enamel:

Martin's (1985) claim that thick molar enamel is primitive for large-bodied
hominids and that thin molar enamel is thus synapomorphically secondarily
derived for the African apes, was based on the application of his data to
an arrangement of taxa wherein humans and the African apes constituted a
clade to which the orangutan was more distantly related.

Most recently, G. Schwartz (2000), although presenting detailed data on
enamel deposition and thickness within the crow and between different
teeth, did the same as Martin: interpret the phylogenetic 'history' of
hominoid enamel thickness in the context of an assumed closer relationship
between humans and the African apes than between Homo and Pongo.

His claim that thick molar enamel is intrinsically different in the latter
hominoids is further confounded by incorporating theories of function and
adaptation first into his phylogenetic assessment, rather than, more
neutrally, the other way around.

On the basis of his data, humans and orangutans are delineated by thicker
molar enamel than the African apes, and humans are distinguished from the
orangutan in having even thicker enamel in some regions of the crown. The
phylogenetic conclusion from the data would be that Homo and Pongo are
synapomorphic for thick molar enamel, and Homo autapomorphic in its
differences.

John Grehan

>As
>for the "long hair" character, I strongly suspect it should be thrown out as
>a synapomorphy as well.
>         ------ Gotta run,
>                     Ken
>****************************************
>>From: John Grehan <jgrehan at SCIENCEBUFF.ORG>
>>Reply-To: John Grehan <jgrehan at SCIENCEBUFF.ORG>
>>To: TAXACOM at USOBI.ORG
>>Subject: Human-orangutan phylogeny
>>Date: Thu, 10 Apr 2003 12:25:40 -0400
>>
>>Some TAXACOM respondents earlier comments on the plethora of morphological
>>'evidence' for the human-chimp clade in terms of number of characters or
>>number of papers. I am continuing to examine such papers and I am beginning
>>to wonder whether the numbers will really add up to anything.
>>
>>Right now I am reading through a paper by Collar dand Wood (2000) How
>>reliable are human phylogenetic hypotheses? (PNAS 97: 5003-5006). This
>>might be cited as another paper providing additional support of the
>>human-chimp connection, but the majority of characters are extracted from
>>Shoshani et al who extract many if not most of theres from Groves (1986 and
>>modified 1995). So one gets a layering of character sources, apparently
>>without any direct individual observation of said characters.
>>
>>Further Collard and Wood extract out only 96 craniodental characters for
>>Gorilla, Homo, Hylobates, Pan, Pongo and an outgroup (Colobus). This seems
>>to result in some strange characters. For example their character 8 is
>>presented as autapomorphic for Pongo so its totally uninformative!  Same
>>for character 24! (which in Shoshani et al is also recorded in several
>>monkeys so its effectively a plesiomorphic character and probably should
>>not have been included at all). There are other autapomorphies (which are
>>probably plesiomorphies in Shoshani et al) as well.
>>
>>They even include characters that are declared to be in the out group. For
>>example, character 26 is in Gorilla and the outgroup! Perhaps I have missed
>>something about cladistic characters, but my understanding was that a
>>character present in the outgroup suggests it is a plesiomorphy within the
>>group analyzed.
>>
>>Character 28 has two states - not developed (0) and developed (1). My
>>understanding of a binary state synapomorphy is for (1) to represent the
>>derived state (which is how the distribution goes most of the time in this
>>paper, but for 28 their distribution is as follows:
>>
>>Homo 0, Pan 1, Gorilla 1, Pongo 1, Hylobates 0, Colobus 1.
>>
>>But the most interesting part of this paper was the tallies for particular
>>clades. There were 11 for Human/chimp/gorilla, 5 for human/chimp, and 10
>>(!!!) for human/orang (despite not taking all the potential human-orang
>>synapomorphies.
>>
>>So on the face of it, 35 characters have been proposed for human-orangs
>>(for which so far I have not seen any clear-cut refutation of any)
>>outnumbers the five proposed by Collard and Wood for chimps, and even far
>>outnumbers their human-chimp-gorilla clade.
>>
>>Collard and wood prejudice their analysis by stating (p. 5004) to support
>>the hypothesis that craniodental characters are reliable for reconstructing
>>the phylogenetic relationships of fossil primate species and genera, the
>>resulting cladogram matched the molecular cladogram, or a partially
>>resolved cladogram comprised only molecular clades or the strict consensus
>>comprised only clades compatible with the molecular cladogram. So here it
>>is clear that the authors do not view morphology as independent evidence of
>>phylogeny!
>>
>>Their parsimony analysis of two quantitative data sets resulted in Homo
>>being the sister taxon of Gorilla-Pan-Pongo (although I found only three
>>characters giving this direct support. There are a lot of mutistate
>>characters and quite a few are confusion in their polarity (eg absent or
>>not known in outgroup, derived state in Hylobates).
>>
>>Their parsimony analysis of a qualitative matrix resulted in a Homo-Pongo
>>in one clade (based on straight numbers for their data this is of no
>>surprise) and a Pan-Gorilla clade.
>>
>>Of course nether of these hypotheses are 'supported' because they do not
>>agree with the TRUE molecular tree.
>>
>>I could add more, but unless I am missing something fundamental (and I may
>>have made some mistakes in what is admittedly a quick reading) it seems
>>that this paper is problematic, not only for its choices and assertion of
>>putative synapomorphies, but also for its prejudice in favor of molecular
>>trees as the truth and arbiter of phylogeny
>>
>>Since there were some very strong orangutan critics posting on TAXACOM I am
>>sure they will be able to demonstrate how Collard and Wood actually do have
>>a robust morphological character set, and also demonstrate that any
>>morphological character not in harmony with phenetic molecular characters
>>should be discarded - and while we are at it throw out all systematists
>>working on morphology since genetics is at the truth of the matter anyway
>>(has anyone yet made this sort of proposal to NSF (or other funding
>>organizations in other countries) to eliminate funding for morphological
>>systematics?).
>>
>>John Grehan
>>
>>
>>
>>
>>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
>
>
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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