Humans and apes

[john Grehan]

Jason de Koning wrote

At 03:50 PM 3/15/2003 -0500, you wrote:
>>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.

I realize that there is probably no absolute agnosticism in presentation of
data to the public. Their conclusions can always be affected by the style
of presentation. I will endeavor to open a wide window such as reference to
web sites dealing with the subject.

>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,

Probably true of any science

>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".

Agreed. The latter qualification is often not mentioned in exhibits - or
that a consensus view has no necessary correlation with being the view
being more correct than any that are not part of that consensus view.

>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.

I've appear to have lost the thread of this. I take it I am disingenuous or
misleading in presenting the public with a scientific debate with
information on how the different views are each supported.

>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.

Some of these 'data' have proved to be problematic. The Shoshani et al
paper refers to an earlier work by Groves (1986). In the list by Groves
(1986) gave, Schwartz found only a few that stood up as synapomorphic, and
most of these were in favor of the orangutan relationship. Shoshani et al
also refer to Groves (1995) which is an unpublished document that modifies
the 1986 data and incorporates somehow the critique by Schwartz, so its
difficult to tease out what is going on. Further investigation may clarify
the matter. I'm in the midst of trying to tease out the characters. As
mentioned earlier, some morphological papers purporting support for a
Homo-African ape clade actually interpreted their characters on the basis
of this being the correct clade in the first place (see papers by Schwartz).

>There are many other types of
>data that reject human-orang, and support human-chimp as have been
>mentioned in this thread.

The only major objection so far has been the molecular data

>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?

If this stands up I would certainly have to reconsider my current
preference. Of course maybe I am obstinate. I continue to support
panbiogeography despite resounding rejection by the majority of
biogeographers (who follow Darwin's method).

>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:

The DNA sequence data appears to be phenetic so I do see how it can
automatically subsume morphology. Schwartz includes some genetic characters
that appear to provide synapomophries and that do support the orangutan
connection


>also demonstrates a misunderstanding of the existing data, and of
>opinion in the field.  No one has ignored the orang hypothesis.

Not true. There are papers that omit any mention of the hypothesis

>Thesimple matter is that it is strongly excluded by the vast majority of
>existing data.

Part of that majority (molecular data) is problematic if it is phenetic.
Another part (morphology) is problematic if the data is not cladistic.

>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?

Not all data is equal - so looking at ALL equally might be misleading.

>Selectively ignoring the majority of evidence in favor of a hypothesis
>that you prefer is simply dangerous:

Well I intend to be selective only in an informed way - i.e I am looking
with great interest to the details of the Homo-African apes papers.

>I also renew my claim that neutrally evolving characters should be
>preferred to those susceptible to corruption by selection.  I

In which case morphology is meaningless, and molecular papers that
originally substantiated molecular trees by their correlation with
morphological trees are also meaningless.

>f 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.

If they are phenetic characters they remain problematic.

>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.

Maybe


>>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.)

I guess I am lost at sea with this. If morphology is misleading and
genetics is not, morphology remains uninformative about phylogeny. Weighing
misleading evidence seems problematic.

John

Dr. John Grehan
Director of Science and Collections
Buffalo Museum of Science
1020 Humboldt Parkway
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jgrehan at sciencebuff.org