On Tuesday, March 21, 2000 9:11 AM Billy Brown bbrown@transcient.com wrote:
> I don't doubt that complex organisms capable of surviving such
environments
> are possible, but I have some reservations about the idea that they could
> evolve locally. Before you can have organisms with lots of elaborate
> adaptations for surviving extreme environmental swings, you have to have
> simple organisms that don't have such adaptations. You need an
environment
> in which life can arise, solve the basic survival problems like energy
> production and reproduction, and reach a level of complexity that allows
> complex adaptations to evolve. That implies that a world that has a
stable
> period followed by wild climate swings may support interesting life, but
one
> that has always had extreme shifts may not evolve life in the first place.
While I agree with what Billy is saying here for the most part, Earth is not
as tame as some might think. Even now, some climatists have proposed that
the Earth has completely frozen over several times in its history and that
rapid climate change followed by stable periods might be the rule. (See
"Snowball Earth" by Paul F. Hoffman and Daniel P. Schrag in _Scientific
American_ 2000 Jan for the former (now at
http://www.sciam.com/2000/0100issue/0100hoffman.html) and "Rapid Climate
Change" by Kendrick Taylor in _American Scientist_ 1999 July-August.) This
is by no means like a highly elliptical orbiting planet scenario, say, of
Poul Anderson's _A Circus of Hells_, or the OnOff Star scenario in Vernor
Vinge's _A Deepness in the Sky_, but it should give one pause.
My two cents!
Daniel Ust
See my Updates at:
http://mars.superlink.net/neptune/
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