Humans and apes

[B.J.Tindall]

There is an article in PNAS:
Rate heterogeneity among lineages of tracheophytes: Integration of
molecular and fossil data and evidence for molecular living fossils
Pamela S. Soltis , Douglas E. Soltis, Vincent Savolainen, Peter R. Crane,
and Timothy G. Barraclough
PNAS 99(7):4430 2002

I am not in a position to judge the accuracy of the data, but it indicates
that one may not be able to apply a "constant" substitution rate.

Michael S.Y. Lee Molecular Clock Calibrations and Metazoan Divergence Dates
J Mol Evol 49:385-391 (1999)
has also pointed out that molecular substitution rates appear to be
calibrated against the fossil record.
Brian

At 17:32 11.3.2003 -0500, john Grehan wrote:
> My main interest here was to find out about whether we might be the first
>institution to present to the an exhibit that the existence of two
>alternative phylogenetic models for apes and humans currently being
>contested by primate systematists. However, a couple of responses about the
>phylogenetic situation invite further comment.
>
> Agnes Dettai wrote
>
> The hypothesis of a closer relationship between man and orang-utan than
>between man and chimp has indeed been dropped entirely to my knowledge.
>
> This is incorrect. The human-orangutan hypothesis is still being promoted
>within primate systematics.
>
>    on our closest relative, then the race is between gorillas and chimps,
>both african apes. (Gibbon(Orang-utan(Gorilla((Chimp,Bonobo),Man))))
>
> This might be the only race in molecular systematics, but not in
>morphological systematics.
>
> Jason de Koning wrote:
>
> There is little doubt left by a wide array of consistent molecular data
>that bonobo and chimpanzee are sister species, separated by only a few
>million years, and that the chimpanzee lineage (including both Pan spp.) is
>the sister group to humans.
>
> While may be little doubt left if one accepts the molecular data as having
>the last word, the orangutan hypothesis presents an alternative that might
>suggest the molecular data is, in this case, incorrect about the nearest
>living relative to humans.
>
> The human-chimp-gorilla trichotomy problem has been resolved molecularly,
>with high statistical support for a number of years (e.g., see papers by
>Mary-Ellen Ruvolo or Morris Goodman for reviews), and is no longer really
>considered a problem.
>
> It remains a problem in the sense that it is incongruent with the set of
>morphological synapomorphies that have been proposed to support a
>human-orangutan clade.
>
> Molecular clock estimates generally place the human-chimp split at about 6
>million years, the gorilla-(human-chimp) split around 7 million years, and
>the orang-(human-chimp-gorilla) split around 14 million years. These
>results are consistent, and the dates are pretty robust to statistical
>methodology and calibration details.
>
> If the orangutan is the sister group then this clock might be wrong. It
>might be that the orang-human split occurred around 14 million years and
>the chimp-gorilla even earlier.
>
> There is not any molecular evidence that suggests that orangutan and human
>could be sister species, to the exclusion of chimps and gorillas. To the
>contrary, all available data strongly excludes that hypothesis.
>
> This is what makes the incongruence of molecular evidence with
>morphological synapomorphies proposed in the orangutan hypothesis so
>interesting.
>
> 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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