Humans and apes

[John grehan]

Jason de Koning wrote

>No.  In my view, not if you represent each hypothesis fairly with respect to
>the supporting and contradictory evidence.

I will do my best on this, and will welcome critique from professionals
that happen to view the product.


>John:
> >The only major objection so far has been the molecular data
>
>While I disagree with this, I think we can agree that if one throws out the
>molecular evidence, there IS more uncertainty.  But why do this?  In the
>field, molecular data gets high precedence on the question because it is
>highly consistent on hominoid phylogeny, not for some automatic reason.

As a phenetic enterprise it happens to be consistent with itself

>Your claim that molecular data is problematic 'if it is phenetic' is
>puzzling to me.  Molecular data is often analysed 'cladistically' by maximum
>parsimony.

The data may be analyzed using cladistic algorithms, but the data (the
characters) themselves are not identified as cladistic in the first place
(i.e. the sequences are not sorted into hypothesized synapomorphies that
can be tested against each other - at least that is my current
understanding. If I am wrong I welcome correction.


> > 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.
>
>Perhaps we don't understand each other here.  Morphology and phenotypic data
>CAN be misleading.  So can genotypic data.  But since phenotypic traits are
>moulded more directly and (probably) frequently by natural selection, they
>become more rapidly skewed away from the underlying historical signal.

This is just a theoretical proposition. Whether it is true is another matter.

>  That doesn't mean that phylogenetic information is unrecoverable.  In
> any case,
>we have no a priori way to identify misleading characters, except by
>comparing them to other characters.

At least in morphology one has an a priori way of distinguishing apomorphic
and plesiomorphic characters.

>Hence, if different characters conflict
>in their phylogenetic signal, we hope that by looking at more characters, we
>can find the 'uncorrupted' historical signal by consensus.  Yes?

In morphology I cans see how different hypothesized derived characters may
come into conflict with each other. I am not sure I can see consensus being
informative other than to draw attention to those areas in conflict.

>Since the hard-tissue evidence is a source of disagreement, have you
>considered the soft-tissue data?  Gibbs, Collard, and Wood (2002; J. Anat
>200: 3-49) analysed data on 171 soft tissues in the hominioids, and
>performed resampling statistics to measure confidence.  Their result was:
>Homo, Pan = 95%; Gorilla, Pan, Homo = 96%.

Not yet. If they have carried out a cladistic analysis of soft tissue
characters it will be very interesting. I know of a blood vessel study that
gives a synapomorphy for Homo-Pongo.

>Interestingly on re-reading this
>paper, they claimed that a statistical analysis of Shoshani's data indicates
>that it does not produce a robust resolution (!)

That would not surprise me.

>Incidentally, would you kindly post the full references to the more recent
>of Schwartz's papers that you've cited in this thread?

Yes, tomorrow where I can pull them out at work.

>There have been
>claims in the literature that Schwartz himself has abandoned the human-orang
>idea (e.g., Begun, 1999 in Parker, Mitchell, and Miles), though I haven't
>seen hard corraboration of this.

It shows that one cannot believe everything one reads in journals or
newspapers. The claim by Begun is not substantiated by the papers he quoted
or ones that he had in mind. Begun admitted to me that he made a mistake
(perhaps an indication of how one's view of a subject can influence one's
interpretation of the literature - a caution for myself as well as anyone).

>If he is still promoting the idea, that does indeed seem pretty unfair...

It seems to be a genuine mistake.

>Best wishes, and good luck with your exhibit.
>- Jason

Thanks. Wherever this leads its interesting and I will learn from the exercise.

John