Re: impacts are cool!

[Dann Pigdon <dannj@alphalink.com.au>]

Michael wrote:

> 
> I can't answer why some things lived and others didn't.  Maybe some
> frogs either burrowed or already were or survived for other reasons.  If
> you kill 99.9% of all living creatures you still have considerable
> biomass hanging around to procreate.  And I don't deny that there were
> other global changes occuring.
> 
        Perhaps inbreeding was a problem after the event (whatever
that was). Small creatures in general tend to suffer less from the
effects of inbreeding. Perhaps dinosaurs had become so highly
specialised that they required considerable populations to provide
a large enough gene pool. If 99.9% (wherever that figure came from)
of all creatures, including dinos, were killed off, perhaps the
0.1% of remaining dinos was not a large enough gene pool. Birds
could have flown large distances to find enough breeding partners
(or perhaps survived on small offshore islands which tend to be
stressed environments at the best of times). Frogs, reptiles, and
small mammals may have been able to continue on through the genetic
bottleneck. Certainly small mammals today seem to be able to inbreed
with few problems (mice for example).
        The bird/pterosaur distinction has always bothered me. Both
could fly, and both were presumably good at it. Most pterosaur
remains seem to be of marine species so I'm not sure we will ever
have a really good fossil sample of their populations. Can we be sure
they were on the decline anyway?

-- 
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        Dann Pigdon
        Melbourne, Australia

        Dinosaur Reconstructions:
        http://www.geocities.com/capecanaveral/4459/
        Australian Dinosaurs:
        http://www.alphalink.com.au/~dannj
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