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Re: of marbles and dinos (was extinction)



Stephen Throop writes that "...the easiest approach is to calculate the
chances that any red marble would be among the 25% that survive...", then, in
the sample of 175 marbles (taken from a population of 700 wherein 100, or
roughly 14.3%, are red) projects that the "...odds are 44 trillion to one
that you will have at least [I believe he means 'only' rather than 'at
least'] one red".

I think there is another variable to be considered here:  a population of
organisms need not be reduced to one in order to guarantee its elimination.
 For all such populations, there is a critical mass below which they will not
survive.  This population size will vary among species, and can be expressed
as a percentage of an existing population.  If there were a 75% elimination
rate among two populations, one which needs 30% of its members to survive a
catastrophe in order for the population to survive, and one which needs 20%
of its members to survive that catastrophe, then we have doomed the former,
but the latter will perpetuate itself, and possibly flourish past its former
levels due to the absence of a competitor; or, if it is dependent upon the
doomed group, it will die off anyway.

These different survival levels may be due to the relative numbers in the
species' population to begin with (which would seem to imply certain members
of the dinosaurs should have made it - and I'm referring to at least some in
non-avian form),  but it will also depend on many other factors, which may
have been the reason the non-avians didn't make it.

Now, as for purely random extinction, I think the marble scenario still works
well to demonstrate the unlikelihood.  We simply need to state the population
survival requirements.  Think of it this way; however many marbles we have in
a bucket, of however many different colours, a 75% extinction rate overall
means, in a random scenario, that in most of the species populations (colour
groups), 20% to 30% will survive.  Only 10% to 15% of the species will have
more extreme results than these.

Now look at the dino extinction.  Doesn't quite fit the random expectations,
does it, unless the dinosaur species all required extremely large individual
survival rates in order to guarantee population survival.  And even then, at
least a few would have been in the 7% or so at the high end of the bell
curve.

BTW:  I haven't computed exact math percentages here, so flame away if you
like, but my point stands: random behaviour, with so many different species
available, demands at least some survival of dinos, in dino form;
intuitively, then, there were non-random factors.

Marbles, anyone?

Wayne A. Bottlick.