Re: Pollen From Permian/Triassic Extinction Show UV Induced Mutations

["David Marjanovic" <david.marjanovic@gmx.at>]

> > OK. But then we need at least 2 causes for the P-Tr mass extinctions.
>
> There is almost always more than one cause for ecological
> events.  That should be the starting point for any discussion on
> extinction.

As you say, "almost"... and why do you assume a priori that a mass
extinction must be an "ecological event", as opposed to caused by factors
outside of ecology?

> > And what could have killed off animals with small
> > adult size but not small juveniles of bigger species?
>
> Recent Nature paper notes that smaller (adult) animals are limited by
> predation, whereas larger animals are limited by food supply--and, there
> is little predation on their juveniles.  Reasons for this are that small
> adults spend more time in an age range that is targeted by more predators;
> juveniles of large animals are just passing through that age range.

When they grow as fast as most extant mammals and birds. Such growth speeds
are rather unexpected for end-Permian fauna. Besides, what could that
predator be that would have been capable of exterminating itself? (I'm
talking about the whole globe and not just California, pardon the pun. :-> )