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Re: Looking for patterns in extinctions.



> 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.

     I'm leaving it alone.

> > Mammals had achieved that zenith in reproductive security -
> > placental birth.

     This reproductive method might pamper the offspring, but it does
not neccessarily mean greater reproductive success.  Keep in mind that
if something happens to the mother, either during pregnancy or before
the newborn becomes fully independant, the babies are screwed anyway.
It also may be a mistake to assume that placentals have a superior
reproductive strategy just because they are more succesful than
marsupials nowadays.  Marsupials held thier own against placentals
through most of the Cenozoic.
     I've also heared the argument stated that mammalian reproductive
strategy beat out the dinosaurs.  However, although you do see some
big (Mesozoically speaking) mammals toward the end of the Cretaceous,
saying they could have been in direct competition with any but the
smallest dinosaurs is absurd.  The mammals didn't drive the dinosaurs
to extinction, they just picked up the ball afterwards.

> 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.  It is a well-known ecological principle that
> predators do not consume their entire food supply.
                      
     Is this an evolutionary tactic of the carnivore or the prey?  A
predator eating up all the prey animals, or a egg eater eating up all
the eggs may be bad in the long term for the eater, but it has more
immediate repercussions for the eaten.  I think well hidden nests,
defense of nests, and the evolution of defensive tactics by prey
animals is a more likely deterrent for overkill than consumptive
abstinance on the part of the carnivore.  When varanids raid a
crocodile's nest, they eat until there are no eggs left or mom chases
them away.  I for one think Red Queen makes perfect sense.  Besides,
it seems to me that predators or egg eaters muching too many prey
animals or eggs during poor reproductive seasons could be a cause of
extiction.  I also just made up the term "consumptive abstinance" on
the spot and am very proud.
 
LN Jeff 0-
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"People say I'm tough, and I am tough.  People say I'm a bastard, and I'll 
tell you what...I AM a bastard.  A tough hard bastard with a pumpkin for a 
head."