Re: Theories on the extinction of dinosaurs

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

On Fri, 19 Nov 1999 Dinogeorge@aol.com wrote:

> the impact not happened. Perhaps there would have been a general decline in 
> dinosaur diversity through the Cenozoic paralleling a general rise in small 
> mammal diversity.

Why?


> Perhaps a few new dinosaur groups would have evolved, and 
> there might have been a greater diversity of large flightless predatory birds 
> (the "new theropods").

Then you need an explanation why for this didn't happen.  In
almost every case of extant large flightless birds, predation by
_much_ smaller mammals appears the principal limiting factor.  Competition
with mammals is seldom observed.  My question is: Why would this not
happen in any case to limit the "new theropods"?

> Doubt that anything like humans would have appeared 
> among the mammals.

Well, humans are so far down stream of 65 mya, such speculation is
meaningless.  A more useful statement might be: Primates would not have
evolved were it not for the extinction of non-avian dinosaurs.  But this
would be hard to justify sincethe two groups may never have come into
contact with each other.