genetic tress and human evolution

John Grehan jgrehan at SCIENCEBUFF.ORG
Thu Aug 5 09:24:59 CDT 2004

In reference to earlier observations about genetics as the reliable and
necessary indicator of primate (or any) phylogeny I found the paper by
Ruvolo and Koh (1996: Proceedings of the National Academy of Sciences,
USA: 5(2):439-440) to be rather interesting. They re-ran a data set for
the dompanmine D4 receptor gene from other authors and get the same
result which is two most parsimonious trees - one involving a
Pan-Gorilla clade sister group to baboons and Rhesus, in turn sister
group to orangutan and then human - the other with the Pan-Gorilla clade
in an unresolved trichotomy with orangutan and Old World monkeys (the
position of humans was not mentioned). 

The authors dismiss the trichotomy because it conflicts with long
accepted arrangements supported by molecular and non-molecular evidence
and orangutans comprise the "well-accepted sister group to the African
hominoids) on the basis of morphological and molecular studies". Of
course there the published orangutan evidence is conveniently left out
of the picture. They conclude that the consensus tree violates commonly
held, noncontroversial hypotheses about primate evolution which are
based on a large body or morphological and molecular data. 


The other tree is dismissed as "phylogenetically meaningless because
"accepting it is equivalent to accepting a radical revision of primate
phylogenetics, one which flies in the face of all other data". 


The authors end by explaining away the results as errors resulting from
the use of genes containing tandemly duplicated repeats. It is quite
possible that they are right, but what interests me most is that it is
possible for molecular geneticists to find genetic arguments dismissed
genetic results that one does not like. Interestingly, they point to
another study involving tandemly duplicated repeats (involucrin) also
supports a Pan-Gorrilla clade. Errors aside, the indication of a
Pan-Gorilla clade may actually be phylogenetically informative as there
is considerable morphological cladistic evidence of such a relationship.


John Grehan



John R. Grehan
Director of Science and Collections

Buffalo Museum of Science

1020 Humboldt Parkway

Buffalo, NY 14211-1193

email: jgrehan at

Phone: (716) 896-5200 ext 372


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