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Re: Extinction



On Sat, 30 Nov 1996, Steve Jackson wrote:

> Interesting discussions about the "stochastic" mode of extinction, either
> species or mass 

This idea doesn't apply to dinosaurs at the K/T--at least no one here has 
yet explained how it applies.  Merely stating the idea doesn't make it 
fit.  For example, if I have a hundred green marbles representing mammal 
species at the K/T and a hundred red marbles representing dino species 
(arbitrary numbers), the probability of picking ALL red marbles at random 
is close to zero!!  And yet this is what happened at the K/T.  Some 
non-random causative force was at work. 

> the idea that eventually enough bad things happen at once
> that a species, or group, is pushed below the level at which it can
> maintain itself.

What bad things happened to do this?  And why did they do it more to 
dinos than other species?  If you shoot all but one deer in your 
forest--and this deer dies from an accidental fall--it is wrong to say 
the species became extinct randomly.

> And, of course, the disappearance (or near disappearance) of one species is
> usually a Bad Thing for some other inhabitants of its biome, often in
> unexpected ways. (Some butterflies get significant nutrients from carnivore
> droppings; thus, if big carnivores become rare, butterfly reproduction is
> threatened.)

This sort of complex species' interaction is exactly what I am arguing 
for.  And yet, even it argues for physical complexity as the cause 
for extinction, i.e., enough bad things happening (sea level cha., 
anoxia, bolide, vulcanism) the current paradigm _ignores_ biological 
complexity as a contributory factor.  Just because we don't know what was 
going on in the biotic realm, doesn't mean nothing was going on.  We 
can't, therefore, pretend we know what killed all the dinosaurs.
 
> Disease might be a good example here. Granted that a disease is very
> unlikely to kill off 100% of a species. 

An example of limited value.  What you are postulating is that a disease 
(or series of diseases) killed of not 95% 0f _a_ species, but 95% of 100% 
of all dino species.  This isn't likely.  And the idea ignores the 
ability of dinosaurs to recover rapidly from this sort of threat.