Re: GEOLOGY/SETI: The moon and plate tectonics

From: Robert J. Bradbury (
Date: Thu Jul 12 2001 - 23:33:10 MDT

Mike wrote:
> Very interesting, and corroborating my earlier statements about large
> moons being necessary for intelligent civilizations.

Mike, I believe you are making at least one unsubstantiated leap.
The development of "intelligent civilizations" would appear to
depend in large part to the "rate" of evolution from simple
organisms to higher organisms. The existence or lack of existence
of large moons may effect the geology and length of the liquid
water period of a planet, but there is very little evidence
(since we only have 1 data point) regarding the relation between
those phenomena and the evolution of intelligence. We know for certain
that the mutation rate for an organism can vary over a wide range
(contrast HIV with Deinococcus radiodurans). Constraints on mutation
rates for higher level organisms are far from certain. The most
recent evidence from comparisons between the Mouse & Human genomes
suggests that factors that influence gene duplication and successive
adaptations may play a key role in the rate of evolution. So
the development of intelligence may depend on two quite different
genetic mechanisms (gene duplication & gene mutation rates) which
may be independent of each other and have a very wide range of
possible values.

Geologists & astronomers can make all the arguments they want to
about "Rare Earth's" and while those arguments will be interesting
they are not "trump cards" because biology can compensate for
a very wide range of environmental variables.


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