[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: The extinction of small dinosaurs (long again)



Don't worry, I'll shut up on this thread at least until Thursday.

Original Message by John Bois
Friday, 13 December 2002 14:49

> A sobering fact is that there is no direct evidence for _any_ extinctions
> except those recorded by humans--

None of them remotely comparable with the K-T, including the plankton 
extinction.

> A strange science it is that rejects _known_ extinction causes

The present is not the key to the past. The past is the key to the present, 
and to the future. Only because we've never seen it doesn't mean...

> (perhaps because they are less
> spectacular and are going on, as you say, all the time)

Over here a whole generation of scientists (well, almost...) regards 
"science" and "spectacular" as opposites. Peculiar accusation, therefore. :-)

> I'm not saying catastrophies don't cause
> catastrophic extinctions; I am saying that specific direct causes
> involving competing and preying species cannot be ruled out without good
> reason.

The good reason is that a) there is no evidence of competition; b) we have a 
catastrophe, so we _have to expect_ a catastrophic mass extinction _a priori_.

> I don't see the distinction: if a new behavior evolves that results in a
> competitive advantage, that species' range will increase at the expense of
> others'.

If their ranges don't already overlap. Border wars between species are AFAIK 
very rare.

> Some species go out quickly, some slowly.

If you leave them, instead of burning down their habitats with an impact.

> Only the most radical of proponents of punctuated
> equilibrium would suggest that _all_ speciation involves catastrophy.

Actually AFAIK nobody does, because punctuated equilibrium is not about 
catastrophes, it's about evolutionary stasis and allopatric speciation.

> If it is true that speciation may be slow or fast--depending on the
> individual circumstances, my feeling is that as species develop new, more
> complex, strategies and behaviors,

Why "more complex"?

> The great changes in
> utilization of ecospace through geological time

What do you mean?

> And yet, we see a disappearance of smaller pterosaurs without a major
> shift in _physical_ conditions.

Actually, we don't see much in the first place. Who says the 
Cenomanian-Turonian mass extinction didn't do it, for example? We have far 
too few fossils to tell. Any opinions by our pterosaur experts?

> There may well have been a major shift in
> biological conditions: competition/predation of birds.

*Boluochia*, for example, is at least as old as even the disappearance of 
anurognathids alone.