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Re: paleontolgist, dinosaur



[This might get a bit confusing; I didn't distribute the message to
 which Stan is responding (too much quoted material), but I did
 distribute an ammended version.  The version I distributed already
 addressed some of what Stan writes below even though John hadn't seen
 *this* message yet.  Fortunately (for me) I'm going out of town soon,
 so Nedin will have to straighten out anything that's still crooked.
 -- MR ]

From: John Bois <jbois@umd5.umd.edu>
 
> > True, but there is precious little evidence that the extinctions
> > did target the dinosaurs specifically.
>
> Since we are talking about terrestrial animals I beg to differ.  
> Non-avian dinosaurs were the _only_ group to be completely wiped out.  
> This is specific targetting worthy of a smart bomb.

 From a stitistical point of view there is not really that much
difference between 80% extinction and 100% extinction. And there
*were* several other terrestrial groups that showed 75-90% extinction.
It may well have been essentially accidental that non-avian dinosaurs
suffered 100% extinction instead of 90%.

(Also, since birds are so closely related to the maniraptors, I do not
think we can really call the dinosaur extinction 100% - here, at least,
I think the cladists have a valid point)

 > This might be true.  But I return to my original qualm: relating the 
 > events to the pattern of victims and survivors has not yet been done 
 > effectively.
 > ...
 > > When there is evidence that no one suspect could have done the job
 > > alone
 > 
 > ...this sounds like famous last words!  What evidence exists that rules 
 > out a suspect who is not yet a suspect.  ...

Are you suggesting thast NONE of the suggested causes was involved?

I am skeptical of this as at this point almost all imaginable causes
have been considered (even highly unlikely ones), and, as you say,
none. by themselves, really matches to the pattern of victims and
survivors.  This is why I say that none alone can do the job - no
one factor would produce the observed pattern.

 > , as Greg Paul points out, and when there is substantial evidence
 > > for the presence of ALL suspects at the scene of the crime, it is
 > > reasonable conclude that there was a conspiracy.
 > 
 > Fine.  A conspiracy if you can explain it.  No one has yet done this

Simple, each factor produces its own set of stresses on the various
species. Each, alone, would cause a few extinctions, and also shuffle
the ranges of the remainder. Together there is a synergistic effect
that amplifies the individual effects.

This sort of synergy is often involved in natural extinctions anyway,
even outside of mass extinction periods.  Not too long ago Stephen
Jay Gould wrote a short essay on the recent exctinction of a snail
that used to live in the sea grass beds off the Atlantic coast.  As
he tells it the extinction was to to the confluence of two or three
factors, none of which alone would have caused the extinction. (And
in fact the snail had almost certainly previously survived each alone).
[I do not remember what the factors were, but I believe an unusually
extreme seasonal temperature was one factor].

 > > So now we not only have the suspects present at one crime scene, but
 > > the *same* suspects present repeatedly at other crimes of the same
 > > type.
 > 
 > But, again, nothing relating any of this to the fossil record of victims and 
 > survivors.  If indeed these events did stress out the dinosaurs, why did 
 > they.  I argue they were widespread and resilient. ...

They were resilient to each type of stress *alone*, but they were unable
to *simultaneously* cope with all of them. (Perhaps, for the dinsoaur
physiology and ecological range the required coping strategies were
mutually exclusive, for instance).

In fact this may be the usual mode of extinction at any time.

swf@elsegundoca.ncr.com         sarima@ix.netcom.com

The peace of God be with you.