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Re: Pleistocene & K/T extinctions
Response to John Alroy's posting:
First, I hope you review papers with a bit more consideration of to
differing opinions than your posting on extinction models suggests.
I'm not a particularly avid supporter of the traditional changing-
climate arguments for Pleistocene extinctions, but there are logical
reasons to reserve judgment. Consider, if in N.A. humans extinguished all
that megafauna, who did the same in Europe? Mammoths, mastodons,
wooly rhinos, cave bears, large felids, and Irish Elk (to mention
the noteworthy taxa) all going extinct roughly coincident with the
North Amercican fauna. In Europe, of course, there was no
directed human invasion as there was in North America.
On the K/T boundary, your comment on "needless" debate suggests
that you really are unaware of a great deal of valid counterpoint to
the impact hypothesis. Let me guess: you are a recent graduate or
a graduate student at U. Chicago and the product of an advisor
who is a rabid punctuationist? Not all paleontologists are as sure as you
seem to be that "gradualists" are practicing an obsolete science. Unless
I misjudge your experience, let me suggest you shop around for
differeing ideas than your local orthodoxy.
There is viable, healthy debate about the validity of the Chicxulub
crater as the K/T bolide site (see Meyerhoff, et al., Geology, Jan. '94,
and the flood of papers by Gerta Keller and Charles Officer). If Meyerhoff's
group is correct, there is Cretaceous rock _inside_ Chicxulub, disqualifing
the structure as the terminal Cretaceous phenomenon.
Either way, one need not be a fool or ignorant, as you imply, to find
the evidence for an impact-driven extinction at the K/T boundary
unsupported or weak. My observations of K/T boundary terrestrial
and nearshore marine strata suggests that the general fauna was stressed
well below the boundary horizon, which tends to support a gradualistic model
for the mass extinction.
The most important element in scholarly analysis is an open mind, followed by
good data, and judgement, third. Its called the "Scientific Method." Try it.