I understood that the early Earth atmosphere model now had less emphasis on
methane due to its vulnerability to solar photodissociation. Has this fallen
from favour and if so can anyone explain to me why?
Secondly, where bone is concerned, so far as we know this tissue type
appeared but once in evolutionary history and all animals which have it
derive from that common ancestor. ET life cannot be expected to 'invent'
bone but we can anticipate the emergence of structural materials of some
Finally I'm not so sure either that the 'rapid' three million year cycle of
drastic habitat changes would encourage evolution before the formation of
fully nucleated cells, eucaryotes. Recent research indicates that a long
period of of climatic stability, perhaps billions of years, was required for
their emergence as it required the gradual assimilation of symbiotic
lifeforms into a new lifeform
Bottom line - I agree smart techy ETs may be rare.
ET-Presence - http://www.et-presence.ndirect.co.uk
HOGMANAYCON - http://www.ndirect.co.uk/~cb/conpage.htm
From: Ron Blue <firstname.lastname@example.org>
To: email@example.com <firstname.lastname@example.org> Evolution <email@example.com>
Date: 05 September 1998 03:46
Subject: SETI Higher CO2 levels on earth type planets
>When the Mars sized object hit the Earth about 4.5 billion years ago and
>the moon it also blew away the CO2/methane atmosphere. Ultimately, the
>experienced by the earth, 90% of the time, may not have occurred if the
>atmosphere had remained. Rapid changes may be necessary for evolution
>and ultimately the development of intelligent life.
>Standard models of planet formation suggest that the average earth would be
>1.3 earth masses. Such earths would be very warm and have violent weather.
>A large moon is necessary to keep the north/south poles locked into
>for our traditional weather patterns. Planets without a large moon would
>rapid climate changes due to relativity space-time distortions from their
>This would randomly point the planet's north pole toward the star and its
>pole toward the star every 3 million years. This should speed up
>High CO2 levels, however, may result in a loss of bones and may block the
>emergence of animal life on planets. This could significantly reduce the
>technologically intelligent species in the universe.