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RE: Steadman's review of Mesozoic Birds






From: "Tim Williams" <twilliams_alpha@hotmail.com>
Reply-To: twilliams_alpha@hotmail.com
To: dinosaur@usc.edu
Subject: RE: Steadman's review of Mesozoic Birds
Date: Fri, 30 Jan 2004 11:17:21 -0600

John Pourtless wrote:

I have watched and participated in this fracas for about a decade now. And in that time I have abandoned the thecodont hypothesis to which I previously held, but I remain deeply troubled by the tone of the debate amongst professionals and spectators such as myself.

I have to say (and it saddens me to say this) that this is part-and-parcel of scientific debate. Every field of science has its topics that generate a surprising amount of acrimony. To give another example... If you've tuned in to the life-on-Mars debate, you'll know that central to this debate is a certain Martian meteorite (ALH84001) found on Antarctica. This meteorite, which is of undoubted Martian origin, contains microscopic crystals of magnetite that are of a shape and size uncannily similar to those produced biogenically by certain bacteria on Earth. The debate over whether the magnetite contained in the Martian meteorite is indeed biogenic (and therefore indicative of past or present life on the Red Planet) is one of the most heated debates I have seen. (I have heard that some scientists are no longer on speaking terms.)


Vitriolic debate also occurs in other areas of paleontology - as anybody who is familiar with the opposing theories on the origin of _Carcharodon_ (the great white shark) will attest to.

As for the birds-are-dinosaurs debate, this has to be one of the most lopsided debates in the history of science. The notion that birds and maniraptorans are not really theropods, but a separate lineage that evolved independently from other theropods, is utterly bewildering. Mickey is right: this does have an air of desperation to it.

It is nothing of the sort. I merley wish to indicate that cladistics, much like molecular systematics, is not the universal panacea for ornithological systematics.

Molecular systematics actually employ cladistic methodology. Nucleotides (for genes or RNA) and amino acids (for proteins) are the characters that are used. But I would agree wholeheartedly that molecular analyses are not the panacea for resolving phylogenies (for birds or anything else).



Tim


Oh I realize that science contains some of the most passionate blood of all, that is spilled over a multitude of topics. That so much is not what disturbs me, it is the tone of the debate, the accusations and counter-accusations that both sides have made. For instance, it is astounding to see Feduccia on the one hand with a straight face propose that there is some sort of shadowy cladistics conspiracy to pull the wool over ornithology's eyes, but it is equally astonishing to see the very idea that the theropod hypothesis is incorrect, relegated to the realm of quasi-creationist pseudoscience, and with it the denigration of an entire discipline (ornithological systematics). From all I have seen the data which has been presented by the thecodont camp, though incorrect and framed in shoddy and at times outrightly specious contexts, is nonetheless there. The data on the possible lack of homology between the theropod manus and bird manus (which I do not think is the case), 'is' real and valid, even if it has been employed by a questionable and dubious methodology and philosophy of how to represent phylogeny. And that is another thing which troubles me, as I have said before, I am by no means anti-cladistics, but Feduccia and his colleagues 'are' right when they comment on the sheer zeal of some cladists, which they are not alone in noting. Cladistics is but a tool for the resolution of phylogenies, it is not as some people seem to think, the end in and of itself. For instance, to dismiss an analysis for the solitary reason that it does not produce a PAUP generated cladogram, makes no sense to me. Systematists these days seem to forget that much good science was done prior to the advent of the Hennigian system, and the production of valuable and incisive research is not contingent upon a cladistic approach, however useful that approach may be.

And as for molecular systematics for resolving the evolution of birds...we who find it to be anything but the universal panacea for that riddle are, it seems, in the minority.

JGK

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