Humans and orangutans

[STEPHEN MANNING]

At 02:31 PM 6/17/03 -0400, John Grehan wrote:
>Just an update on the orangutan-human front. I have heard from one
>molecular geneticist informing me that it has been scientifically proven
>that chimpanzees are human's closest living relatives and that it is highly
>irresponsible for me to convey to the public information which is known to
>be incorrect and that I will look like a laughing-stock among my peers.
>
>Be that as it may, this geneticist raises the same point I have mentioned
>earlier. If only molecular genetics scientifically proves phylogeny then
>all morphological contributions to phylogeny are rendered science fiction.
>All morphological studies, including those of fossil taxa, are unreliable
>to the point that they should no longer be funded. This seems to be the
>inevitable conclusion one would reach if molecular phylogeny were the only
>reliable way to reconstruct phylogeny and have automatic precedence over
>morphology. This is the view taken by most primate systematists working
>with human origins - even by those who study morphology, and including
>those who study fossil hominid taxa!
>
>Are there any morphological systematists on this list who view molecular
>genetics as the last word on reconstructing phylogeny? (i.e. view their own
>morphological work as phylogenetically uninformative).

Don't knock phenotypes - they reflect BOTH the molecular and environmental
(including developmental) influences that shape an organism and thus are
more potentially informative.  It's just that at this point in time it is
harder to evaluate the environmental influences because there are not
enough data on them.

I believe morphological and molecular data are complementary.  When and if
they conflict my hypothesis would usually be that the molecular genetics is
more reliable, statistically, unless there is some particular factor that
would tend to negate this.  For example, if there is good enough reason to
believe that a particular morphological trait is highly selected for or
against in the context of the particular environment or biological
community in which the organism bearing the trait probably existed, that
should lead to less reliance on the morphology than one might otherwise
accord it.

Also I would think that some of what appear to be rather drastic
morphological divergences may sometimes be not much more than one or a few
genes being left on for longer during development than in an ancestor.  If
this were to lead to a fossil having, just for example, many more segments
than other organisms of the same phylum in the fossil record, there might
be a temptation to accord that fossil a new genus or higher status despite
it being the product of only a single gene mutation.  So at least
superficially the morphological record would be misleading compared to the
molecular one that showed only one or two mutations separated the taxa.  Etc...

I really think in the future, when people are not only able to recognize
base sequences but also identify the functions, if any, of the particular
genes being sequenced, we will be in a much better position to evaluate
reliably how accurate phylogenetic conclusions from morphology are in the
absence of supporting molecular data; or whether conclusions based on
molecular data are more accurate than those based on morphological data
when the two conflict.  That may not be in our lifetimes.

Cheers,
Steve Manning

>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
>http://www.sciencebuff.org/biogeography/Panbiogeography/Panbiogeography-Gate.htm
>http://www.sciencebuff.org/HepialidaeGate.htm

Stephen D. Manning, Ph.D.
Professor of Biology
Mathematics and Science Division
Arkansas State University - Beebe
P. O. Box 1000
Beebe, Arkansas 72012-1000
USA
Tel: 501-882-7162