[Taxacom] real molecular data

John Grehan jgrehan at sciencebuff.org
Thu Nov 13 11:39:16 CST 2008

OK - just to prove I am nuts, I scanned every one of 21,507 sequence
positions for coding data in the Prasad et al 2008 study (Confirming the
phylogeny of mammals by use of large comparative sequence data sets Mol.
Biol. Evol. 25: 1795-1808). The coding sequences produced (by parsimony
analysis) a human-chimpanzee clade followed by gorilla and orangutan.


I found the following (although I admit in advance I may have missed
some. I had a twitch in one eye for a while)


Human-chimp - 2 apomorphic bases

Human gorilla - 1 apomorphic base

Human-African ape -  20 apomorphic bases

Chimp-gorilla - 1 apomorphic base


These apomorphies were defined as being absent from all other primates -
in this case only 12 species. In morphology this limited sampling would
be usually recognized cladistically as an absurdly small outgroup
representation. The outgroup taxa in this case were:


1 gibbon

1 colobus monkey

1 vervet monkey

1 baboon

1 macaque

1 duski titi

1 owl monkey

1 squirrel monkey

1 marmoset

1 galago

1 mouse lemur 

1 lemur.


The best I think that may be said of the molecular evidence supporting
the human-chimpanzee relationship is that it is 'overwhelming' if one
ignores the non-cladistic nature of alignment, and the small outgroup
sampling that create apomorphies as an artifact of small outgroup sample
size. For example, at site 14,466 there humans and African apes share A
and that would have been an apomorphy if it were not for the inclusion
of that one gibbon where it also turned up.


So my conclusion is that the molecular claims of proving the
human-chimpanzee relationship is more propaganda than science, and more
phenetics than cladistics.


I rest my case (for now).


John Grehan


Dr. John R. Grehan

Director of Science

Buffalo Museum of Science1020 Humboldt Parkway

Buffalo, NY 14211-1193

email: jgrehan at sciencebuff.org

Phone: (716) 896-5200 ext 372




Ghost moth research


Human evolution and the great apes




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