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Re: paleontolgist, dinosaur
On Mon, 11 Nov 1996, Stan Friesen wrote:
> ...there is precious little evidence that the extinctions
> did target the dinosaurs specifically.
Since we are talking about terrestrial creatures I beg to differ. The
non-avian dinosaurs were the ONLY group to be entirely wiped out. This
is specific targeting worthy of a smart bomb.
> > Loss of habitat variety affects _all_ creatures.
> Only those that are restricted in habitat. Widespread species
> would be less affected.
Even by the end of the Cretaceous the dinosaurs were a robust group
exploiting many niches. They were widespread not only with regard to
niches within a locality, they were also distributed globally. So I'm
not sure what you mean here.
> That is why I go with a multi-causal model. No *one* cause is sufficient
> in itself to explain the full pattern of extinctions (note, the full
> pattern is critical - not just the dinosaur extinctions).
I agree that it _might_ have happened as you say. But my initial qualm
remains: matching _any_ pattern of events to the pattern of victims and
survivors is speculative at best.
> So now we not only have the suspects present at one crime scene, but
> the *same* suspects present repeatedly at other crimes of the same type.
This is not the exact science that you suggest. Dating of long
gone events is sometimes questionable. Over the expanse of
geological time, poor resolution can make unconnected events seem
synchronous. Claims of periodicity are humbug. The causal
connections between environmental events and mass extinctions are usually
unspecified, yet over-stated anyway.
I believe this is a proximate/ultimate cause issue. I think I
might have gone down this path before (I promise I wasn't planning to),
but bear with me. In the following scenario, which is the ultimate
cause, dino reproductive strategy _or_ environmental stress?
Due to habitat loss, vulcanism, ocean anoxia, and a recent
photosynthesis-slowing bolide strike, plant production is down.
Herbivores, which must eat constantly to stay nourished are in
trouble--it is egg-laying season. There are many hungry predators around
desperate to eat anything, including delicious eggs. This makes
nest-guarding imperative. Usually, one parent leaves the nest, eats a
while and returns to relieve the guard. But now, since they have eaten
down all the nearby vegetation, the parent must travel further. The
guard gets too hungry to stay and leaves the nest. Predators help
themselves to the next generation. On the other hand, mammals feed with
their young sakely tucked iside their abdomens, turtles lay and forget,
birds put their eggs in out-of-the-way places and forage broadly.
For argument's sake, assuming for a moment this is what happened,
the ultimate cause of dino extinction, since only they became extinct, is
the non-stealthy egg! The environmental effects were only the proximate
Now, I'm not saying this _is_ what happened, only that claiming
environmental stress--events--as ultimate causes does not have sufficient