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Re: Extinction



Paul Sparks more debate with:

> And then Mickey Rowe kicked in with the slow die off fossil record
> thing.

Sorry about the pun, but I couldn't help it.  I didn't say there was a
slow die off.  I quoted Michael Williams who concluded that there is
no evidence for a catastrophic die off.  It is a subtle but important
distinction.  

> I'm a bit confused but I thought that I read in Science a couple
> years ago that there was a definitive study done that in fact showed
> the opposite when one looks at all the record.  

It was four years ago.  Time flies :-)  The paper in question was
written by Peter Sheehan et al.  Peter is on this list.  I was sort of
hoping he would comment.  In any case, the work reported in that
_Science_ paper played a big role in the Williams paper.  Williams
quotes the paper (I'm quoting Williams):

     The analysis of 556 individuals (Sheehan et al., 1991 footnote 6)
     is said to "show no evidence (probability P <= 0.05) of a gradual
     decline of dinosaurs at the end of the Cretaceous."

Combine this conclusion with the previous one and you can conclude we
don't know anything :-)  It's a bit more complicated than that, of
course.  I recommend again that you find a copy of the paper and read
the whole thing:

Williams, M. (1994). "Catastrophic Versus Noncatastrophic Extinction
     of the Dinosaurs: Testing, Falsifiability, and the Burden of
     Proof", _J. Paleont._, 68(2):183-190.

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)