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Re: Looking for patterns in extinctions.



On Sat, 13 Apr 1996, John Bois wrote:

> In addition, when one considers
> that the overwhelming number of creatures over 25kg. _were_ the
> dinosaurs, the claim becomes tautological.  

How about when one also considers the extinctions of plesiosaurs, 
mosasaurs, pterosaurs, and very large crocodiles--all of which had many
members over 25 kg.

> Why did the dinosaurs succumb taxon-wide
> to these pressures when other taxons didn't?  

As I probably need not point out, dinosaurs did not succumb taxon-wide.  
True, all ornithischians and sauropodomorphs died, but only some of the 
theropods did.

BTW, I'm not picking on you in particular, but I see this a lot:  the 
singular for the word that means a group of related species is "taxon," 
and the plural is "taxa."  Know your Greek!

> Maybe we'll never know what incredibly complex series
> of interconnected factors did them in.  

Probably not.

>      Laying eggs out in the open, in light of the ever-increasing
> egg-predation ambience of the Cretaceous, was a defunct strategy.
> For the dinosaurs, genetically malleable as they were, this was a
> fixed liability.  

I find this difficult to believe.  How, then, did concealed nests ever 
develop in birds?  I think it's probably just that the only nests we've 
been able to find so far are ones made out in the open.  There were 
egg-eaters all throughout the Mesozoic (in fact, there have probably been 
egg-eaters since animals first began laying eggs!), so that does not 
explain why they finally suddenly wiped out the dinosaurs, all over the 
world, at the time of the K/T.

BTW, don't ostriches and other large birds nest in the open to this day?

> I'm talking about the mammals and the birds, both of whose
> diversification was perhaps coming to a sort of functional
> branch-point at the end of the Cretaceous.

I was not aware of this.

> Birds were essentially modern in their flying ability.

What does this have to do with your argument?  Besides, there aren't a 
lot of bird species that eat eggs.
  
> Mammals had achieved that zenith in reproductive security -
> placental birth.

Security for the offspring, yes, but greatly increased danger to the mother.

> It is a theory which explains a lot.  But it has one problem: no
> evidence!

That is a big enough problem in itself, but the theory has other problems, 
too, the utmost of which is this:  it is highly unlikely that egg-eaters 
will eat all the eggs, and it would be (ecologically speaking) stupid of 
them to do so.  They would be cutting off their own food supply.  Nature 
has feedback systems to prevent this sort of phenomenon.

> The iridium layer is merely phenomenon.  

Huh?  What in the world do you mean by this?

> Even if it indicates an extra-terrestrial visitation, this is not a
> cause, only an event!

True enough, but it is an event which might be expected to have some 
pretty serious repurcussions on the environment!

> The scientific literature is full of instances where hard physical
> evidence is misinterpreted and extrapolated out of reason.

Extrapolated out of reason?  Like extrapolating that the mammals and 
birds would eat every last non-avian dinosaur egg?

> We do _not_ know what killed the dinosaurs.  

I agree with you here.

> The non-stealthy egg theory is parsimonious in that it depends on
> well known ecological principles.

It is a well-known ecological principle that predators do not consume 
their entire food supply.

> The pattern makes sense.  It is, in fact, the _only_ comprehendible
> pattern to be observed in the extinctions around the K/T.

I disagree.  What, for instance, happened to the pterosaurs, plesiosaurs, 
and mosasaurs??

Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(206)535-8206
PharriNJ@PLU.edu