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Re: _Night Comes to the Cretaceous_

> Well, background extinctions have a multitude of contingent explanations, of
> course. Indeed, it is this fact that makes a mass extinction so strange: How
> could all those different extinctions, with all those different, complex
> causes, just happen to coincide and line up so that the whole shooting match,
> on all continents everywhere at once, vanishes? I think it's even more
> unlikely than that birds evolved flight from the ground up.

There is nothing all that strange about a mass extinction, if you understand
ecological dynamics.  It's entirely possible for one element to get out of
alignment and have a massive destabilizing effect.  An unstable ecosystem is a
vulnerable ecosystem, and it can fall apart in a shockingly short amount of
time.  If something wipes out the top predator, for example, unpreyed herbivores
can strip the land bare and eat themselves into starvation.  Or if a new type of
plant appears which spreads rapidly and which none of the big herbivores can eat
-- kudzu or spurge, for example. Or a fungus or microbe that parasitizes a large
array of species like _Pfiesteria_, the infamous "cell from hell" that has been
ravaging the fish populations along several parts of the East Coast every year
for several years now.

> Finally, where is it written that >all< extinctions must have a complicated
> explanation? Sometimes, I dare say, the explanation is >trivial<: the earth
> was smacked by a 15-mile-wide comet nucleus, and almost all the animals and
> plants were roasted. That's that. We're not explaining >all< extinctions via
> impacts, just one--the big one at the K-T boundary.

True.  Maybe the impact hypothesis is right.  It's attractive, it explains the
direct physical evidence, and it certainly satisfies the human desire for big
spectacular phenomena having big spectacular causes.  But it doesn't explain all
the evidence, and past experience shows that neat and simple explanations for
ecological breakdowns are more often wrong than right.

-- Jon W.