[Taxacom] molecular nonsense?
jgrehan at sciencebuff.org
Thu Nov 6 08:49:10 CST 2008
Ebersberger et al (2007) Mapping human genetic ancestry. Mol. Biol.
Evol. 24: 2266-2276
I am grateful for one list member sending me the above work as "rather
relevant for your questioning of the (human, chimp) relationship"
It certainly is, and illustrates what I see as continuing illusion of
the putative chimpanzee-human clade. The paper uses a likelihood
approach (correct me if I am wrong, but I understand that this approach
sort of models what the true tree is supposed to be in the first place)
to "identify those sequence trees that significantly reject chimpanzees
as our closest relatives, that is, are incongruent with the species
tree". There you have it, anything that does not fit must be wrong. The
authors begin with the human-chimpanzee assumption and interpret
everything from there. This seems to me a continuance of the molecular
Cladistically the taxonomic sampling is nonsense. To evaluate
relationships of humans and great apes the outgroup is just one monkey
species! The authors also admit that they have no information on the
quality of the individual aligned sequence reads! Amazing! Is this the
standard of systematic quality for molecular analyses? Imagine the
response if a morphologists tries to say that they had no information on
the quality of morphological homologies! The authors then proceed to
invent the quality through a series of computational manipulations to
somehow make the data good. They end up with 30,112 multiple sequence
alignments that are available upon request (I will be requesting).
The authors "re-estimate the splitting times for the human and great ape
lineages." Hmmm - wonder why they have to do that. If molecules are
supposed to give the right answer, then why revisit what has already
been determined? On p. 2274 the authors node that "it is still unclear
when in our evolutionary history we split from the ancestral species
shared with the chimpanzees. Hmmm - maybe because the theory is wrong in
the first place!
"Particularly puzzling in this context is the apparent discrepancy
between the dating of this split based on genetic evidences and the age
of fossils." Well, their answer in short is that the fossil record is
wrong because morphology is wrong! They state "The unequivocal
assignment of fossil remains to a species more closely related to humans
than to chimpanzees based on the presence of certain human-specific
apomorphies should, therefore, be taken with a grain of salt"!!!!! This
authoritative statement mirrors what Jeff and I have been saying for
some time - if only DNA can be relied upon to give the right answer then
the entire fossil record is scientifically meaningless, and now some
molecular experts are saying the same thing! All you morphological
systematists - you are going to be out of job.
Anyway, they note that the "current interpretation of the fossil record
argues for the presence of hominids already at 5.8 MYBP" and possibly
earlier. The molecular study manages to come up with the 'right' answer
divergence estimate of 5.7 Ma (2270) Believe it or not.
There is more! P. 2274 there is a general denouncement of morphological
cladistics! "The problem with using apomorphies for the reconstruction
of phylogenetic relationships, however, extends beyond the
classification of fossils".
"Because gene products essentially defined the phenotype, we can expect
a certain proportion of derived morphological characters to support the
sister grouping of humans and gorillas, or chimpanzees and gorillas"
[but for some strange reason, not humans and orangutans!]
So here you have it, on the authority of these expert molecular
systematists, morphological cladistics is dead!!! (As I have said
before, it baffles the boffin in my to understand why morphologists are
so willing (desperate) to make themselves slaves to molecular
Am I the only one on this list that thinks this molecular stuff is
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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