Re: paleontolgist, dinosaur

[John Bois <jbois@umd5.umd.edu>]

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.

I said:

>  > 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 
cause.

        Now, I'm not saying this _is_ what happened, only that claiming 
environmental stress--events--as ultimate causes does not have sufficient 
explaining power.