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Re: Extinction



Interesting discussions about the "stochastic" mode of extinction, either
species or mass - the idea that eventually enough bad things happen at once
that a species, or group, is pushed below the level at which it can
maintain itself.

This works for unrelated groups as well. The more bad things happen at
once, the more likely it is that a given group will be affected by ENOUGH
of them. Then you get a "mass" extinction.

And, of course, the disappearance (or near disappearance) of one species is
usually a Bad Thing for some other inhabitants of its biome, often in
unexpected ways. (Some butterflies get significant nutrients from carnivore
droppings; thus, if big carnivores become rare, butterfly reproduction is
threatened.)

Furthermore, we are seeing more and more evidence that adaptive radiation
can take place very quickly when a niche is vacant. And a species knocked
down to a few percent of normal levels leaves, effectively, a vacant niche.
So, if a species is in trouble, it might be prevented from recovering, and
eventually driven to the wall, by a newly evolved competitor not subject to
the same stresses!

Disease might be a good example here. Granted that a disease is very
unlikely to kill off 100% of a species. But if it kills 95%, and if it
keeps the species at 5% of normal levels for a few hundred generations,
something else just might radiate into that niche before genes for immunity
can spread through the injured species. Or the genes for immunity might be
linked to other characteristics, creating a quick genetic drift and
producing a daughter species, different in other ways, which outcompetes
the remnants of the parent species.


 Steve Jackson - yes, of SJ Games - yes, we won the Secret Service case
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