[Taxacom] hominid challenge and Pavetta challenge
jgrehan at sciencebuff.org
Thu Sep 24 07:48:30 CDT 2009
The description given below by Barry is EXACTLY the situation presented by molecular supporters working with the fossil record. In a sort of Janus-like manner, from one mouth morphology is said to be completely misleading and only molecular evidence gives the truth for living taxa, out of the other mouth morphology is said to be totally reliable that we can scientifically recognize the phylogenetic position of a fossil and connect it with the living.
A classic example is represented by the paleoanthropologist David Pilbeam who views morphology as unreliable while at the same time pushing morphology to the limits of credibility in arguing for the hominid status of fossils such as Sahelanthropus.
On the basis of morphology Pilbeam once staked his reputation on the fact (note that emphasis as it is now used for the chimpanzee theory) that the fossil Ramapithecus was a hominid, or at the very least a close hominid relative. Then it was found to have orangutan affinities, and since orangutans were, by definition, not as close to us as African apes, Ramapithecus was disowned. The case was then sealed by the molecular evidence. Never mind that the orangutan evidence actually supports, at least in part, Pilbeam's initial argument. Pilbeam once said he would "never again cling quite so firmly to one particular evolutionary scheme", but then he found.....
> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> bounces at mailman.nhm.ku.edu] On Behalf Of Barry Roth
> Sent: Wednesday, September 23, 2009 7:31 PM
> To: Taxacom
> Subject: Re: [Taxacom] hominid challenge and Pavetta challenge
> It's not up to me to answer on behalf of John, but I take his question as
> a serious methodological one: if we accept, on the basis of molecular
> results, that morphological evidence is unreliable, how can we turn around
> and, in a case where molecular data are unavailable, accept the available
> morphological evidence as trustworthy?
> I suppose this could be justified as "you work with what you've got," and
> that is of course a familiar situation for paleontologists. But if a
> whole modality of data is dismissed as unreliable, then you shouldn't be
> able to cherry-pick the situations where you accept and trust it. At
> least not if consistency -- rather than special pleading -- is considered
> a virtue in phylogenetic analysis.
> Barry Roth
> --- On Wed, 9/23/09, Stephen Thorpe <s.thorpe at auckland.ac.nz> wrote:
> We have already been over this ground, John:
> There is less reliable evidence for establishing relationships of fossil
> taxa (cf. extant taxa), both because no molecular evidence is available,
> and also because less morphological evidence is available anyway! Tell us
> something we don't know! It doesn't make it completely unreliable ...
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