Humans and apes

[Jason de Koning]

> John Grehan:
> From a science education point of view the number supporting a
> particular view being contested in the literature has no bearing on
> the matter.

That depends strongly on "the matter".  If the matter is to
agnostically present data to the public in order to allow them to draw
their own conclusions, than perhaps you are correct.  But given that
the tools of inference, hypothesis testing, and deduction are quite
complex in evolutionary biology, and  frequently require some
specialized training to wield effectively, I have my doubts that this
is "the matter".  If, alternatively, the matter is to present popular
hypotheses, and the evidence supporting them, I think you must be dead
wrong.

It is not a fallacious "appeal to authority" to represent a consensus
view among experts as the "scientific truth", if one qualifies that
truth here means "the best supported hypothesis given available
evidence".  There is always debate, whether for good reason or not.  To
be egalitarian about presenting hypotheses to the public is
disingenuous and misleading, as Brian suggested earlier.

This particular issue of the closest living relative to humans is not
an issue of molecular versus morphological perspective, as you seem to
want to dogmatize it.  The vast majority of morphological data give
(((human, chimp) gorilla) orang).  The Shoshani et al. paper I referred
you to earlier presented 267 characters that resolve this relationship,
to the dramatic exclusion of human-orang. There are many other types of
data that reject human-orang, and support human-chimp as have been
mentioned in this thread.  Why do you think that Jeff Schultz's 35
synapomorphies should be preferred to the hundreds of morphological,
behavioral, and cytological characters that are all consistent in
supporting H-C and rejecting H-O?  How can you explain that the
hypothesis most supported by morphological data (HC) is also supported
by millions of molecular characters.  It is not just DNA sequence data
that is consistent with the majority of the morphological data, but
also transposable element data, protein sequence, even gene expression
data (see Enard et al., from Science last year on gene expression
evolution in primate brain).  Your statement:

> John Grehan:
> ...that the chimps are our nearest living relatives is simply not
> true. It would be true with the
> caveat that the great majority of primate systematists accept the
> chimps
> (plus or minus gorilla) as our nearest living relatives. However, the
> orangutan hypothesis is not ignored by all those in the discipline of
> primate systematics who oppose it.

also demonstrates a misunderstanding of the existing data, and of
opinion in the field.  No one has ignored the orang hypothesis.  The
simple matter is that it is strongly excluded by the vast majority of
existing data.  Therefore it is not considered a viable hypothesis.
Hence my peanut-butter sandwich analogy from before: you can find
characters to support all kinds of otherwise implausible relationships.
  The real question is one of balance:  what do ALL the data suggest?
Selectively ignoring the majority of evidence in favor of a hypothesis
that you prefer is simply dangerous:

> John Grehan:
> That is certainly a major part of it. However, I do admit I have a
> current
> bias towards the orangutan hypothesis. It was my personal reaction to
> the
> hypothesis that it made coherent sense out of a number of hominid
> characteristics that were otherwise problematic - such basic and rather

I also renew my claim that neutrally evolving characters should be
preferred to those susceptible to corruption by selection.  If we are
interested in extracting historical signal from traits that change
through time, the ones that evolve on neutral trajectories have the
lowest probability of being misleading.  Another advantage of using
molecular characters (apart from their abundance, and their relative
selective neutrality) is that we know a lot about their rates of
evolution, and have realistic models to aid in phylogenetic inference.
We also have models that can account for variable selection pressure
along lineages.  The models are not perfect, but it is true that we
have a much more comprehensive understanding of the strengths and
limitations of molecular data, than we currently have for morphological.

> John:
> If that is to be the case, it would seem that there is no point in
> doing any morphologically based systematics, no point in making
> comparisons between neutral gene trees and morphological trees, and no
> point in comparing molecular trees with morphological trees

I don't agree.  There is a point, and the point is to weigh all
evidence when it can be obtained, in order to do our work with
integrity.  (Also, of course, to learn about the continuity of
phenotypic transitions, and the rates of morphological and molecular
evolution, which are interesting for non-systematics reasons.)

Cheers,
- Jason


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   A.P. Jason de Koning, Doctoral student        Email: apjdk at albany.edu
     Department of Biological Sciences             Lab:  (518) 442-4347
     University at Albany, SUNY                    FAX:  (518) 442-4767
     1400 Washington Ave., Albany NY 12222, USA  Mobil:  (518) 210-4504
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