Re: K/T impact (was Re: [for some reason] Tim's theory)

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

On Wed, 16 May 2001, Tim Williams wrote:

> Are you saying that you can explain why certain groups were affected more 
> than others at the K/T boundary?
> 
> (Please tell me that this thread isn't going to lead to "the dinosaurs went 
> extinct because mammals ate all their eggs".)

No, I'm going to tell you that science progresses by rigorous examination
of alternate hypotheses; that the bolide hypothesis for marsupial
extinction is weaker on its face than competition with placentals because
1) replacement is a ubiquitous fact of the fossil record; 2) competition
and predation are phenomena which are observed and
demonstrable; 3) bolide-caused extinction of any organism has not been
observed and may be untestable (this doesn't mean it didn't happen--just
that obserable phenomena that can explain things are preferable to
unobservable phenomena than can explain things)--while lack of food has
been proposed for dino extinction (on account of their greater size)  no
one to my knowledge has proposed _any_ proximal mechanism
for marsupial extinction due to bolide.  

Then, if you subtract marsupials, and birds from the "mass" extinction,
you do not have such a massive extinction and you lose the kind of
umbrella explanation-for-everything provided by uncritical examination
of bolide theories.