Re: Extinction

[John Bois <jbois@umd5.umd.edu>]

On Wed, 22 Mar 2000, Stanley Friesen wrote:

> At 09:59 PM 3/21/00 -0500, John Bois wrote:
> > > 2) Nonetheless, if a bolide hit, and apparently one
> > > quite definitely did, there were a lot of unlucky
> > > frogs on that day.
> >
> >But there is _no_ evidence of this.  How can you say ot happened if you
> >have no evidence.
> 
> Actually, there is a *great* *deal* of evidence that a bolide struck the 
> Earth at about 64 MYBP.

Sorry, I meant no evidence of a bad frog day.

And death of frogs at the immediate crater is a trivial event--as
relevant, say, as a frog being crushed by a falling branch.  We are
talking about global effects.  Sorry for the confusion.

> The debatable issue is whether the impact was, by itself, a *sufficient* 
> cause for the total extinction of non-avian dinosaurs.  (For instance, I 
> suspect that the bolide was so effective only because the ecosystems of the 
> Earth were already stressed from other causes, and the same bolide striking 
> at, say, 34 MYBP would have had little long-term effect).

I agree with this.  And such an approach leaves the issue of real
causality open.  We, are, then, still in the hypothesis-forming stage.