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Re: OCCAM'S RAZOR & THERIZINOSAURS



>Oh yes, some theories predicting feathered dinos have appeared in print -
>but that wasn't the question.  The issue is when we are going to see
>anything about secondary flightlessness (or indeed any theories espoused by
>George) in respectable scientific journals - or especially in summaries of
>the field by "accepted experts"?
>


A good paper to read in reference to this discussion - albeit not from a
dinosaurian perspective - came out last year:

Langdon, J.H.  1997.  Umbrella hypotheses and parsimony in human evolution:
a critique of the aquatic ape hypothesis.  Journal of Human Evolution,
33:479-494.

To be sure, there are some real differences between AAS and BCF:  nearly
*every* "line of evidence" in support of AAS has been refuted, and the
political/social overtones are much starker in the former than the latter.
AAS is scientifically dead, whereas while BCF is nothing more than
speculation, it is still viable speculation.  But I do think there are some
similarities, especially with respect to the charges that it hasn't
received a fair hearing.


Basically, the reason you don't hear more about secondary flightlessness in
nonavian dinosaurs has more to do with the way we approach patterns in
nature and our interest in recovering the simplest explanation for that
pattern.  And I'm not just talking cladistics here - parsimony is
ubiquitous in the scientific community.

At present, the phylogenetic pattern recovered by multiple independent
analyses over the past decade does not support secondary flightlessness.
Secondary flightlessness is an additional assumption placed on the pattern
a posteriori.  Is it a bad assumption?  Not necessarily - but it is
secondary, and hence not parsimonious.

The reason I like the Langdon paper is the fact that Langdon addresses the
popularity of "umbrella explanations" among nonspecialists.  If there's any
hole at all in a given hypothesis, there's some human need to plug it
instantly - hence the rise of umbrella explanations that attempt to explain
everything, sacrificing simplicity for the sake of totality.  Sagan's
*Broca's Brain* makes the same point, albeit not as directly, with a
wonderful discusion/decapitation of Velikovsky's ideas.  AAS tried to
explain purported "holes" in standard models of human evolution, such as
hairlessness and the "breathing reflex."  It turns out that not one of
these "holes" is a hole at all - but if they were, we would be faced with a
choice between a parsimonious hypothesis in accord with the data at hand,
and one that may explain a few additional issues, but requires a much more
complicated pattern not readily apparent from the data.  Guess which one
science goes with.



chris


-=--=--=--=--=--=--=--=--=--=
Christopher Brochu

Postdoctoral Research Scientist
Department of Geology
Field Museum of Natural History
Lake Shore Drive at Roosevelt Road
Chicago, IL  60605  USA

phone:  312-922-9410, ext. 469
fax:  312-922-9566

cbrochu@fmppr.fmnh.org