[Taxacom] voodoo molecualr systematics

John Grehan jgrehan at sciencebuff.org
Mon Nov 3 14:49:39 CST 2008

I'm probably going to drive some people nuts but posting ongoing
comments, but someone may be interested, and at worst all I do is show
my ignorance. I am investigating this widespread notion of the "wealth"
of molecular support for the human-chimpanzee relationships to see if it
is real or imagined. Much of the purported evidence has since been
identified as overall similarity (such as with DNA hybridization), but
sequence data are supposed to be cladistic. I've become even more
skeptical since I analyzed a paper on the molecular systematics of
lemurs and lorises which where half of all sites had the ingroup DNA
base present in one or more members of the outgroup, despite the
outgroup being restricted to a few species. As mentioned before, I bet
if more taxa were used the same would apply to all sites (and hence
showing that the DNA data does not conform to the cladistic requirement
of being unique to the ingroup, or at least very rare in the outgroup).


I started looking at a paper by Saitou (1991) on the molecular phylogeny
of extant hominoids from DNA sequence data. This paper used the neighbor
joining method (which I understand to be phenetic (overall similarity)
rather than cladistic - am I correct?). The data was taken from an
earlier paper by Hayasaka et al (1988) which looked at 12 primate taxa
using NJ method (maximum parsimony being rejected because
distance-matrix methods are "generally superior". The analysis appears
to have had no outgroup. The phylogeny produced the typical
human-chimp-gorilla-orangutan-gibbon-monkey sequence, although it also
produced a tarsier-lemur sequence.


As I started teasing through each column of the data (not easy with such
small print - need a microscope) it seems that there may be no bases
unique to any of the large-bodied hominoids that might provide a
cladistic basis for grouping humans closer to chimps/gorillas than
orangutans. If this is how the "wealth" of DNA data has been explored
then it is possible that the DNA evidence will go up in a non-cladistic
puff of smoke - and I haven't even brought up the alignment farce. More
to come no doubt.


John Grehan


Hayaska et al (1988) Mol Biol Evol 5: 626-644

Saitou (1991) am j phys anthro 84: 75-85


Dr. John R. Grehan

Director of Science

Buffalo Museum of Science
1020 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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