On Sep 26, 2005, at 5:51 PM, Alberto Monteiro wrote:
Warren Ockrassa wrote:
This raises the question of why it was that life seemed to sit and do
nothing for a very long time — nearly 3 billion years — before
exploding into the pre-Cambrian diversity that it held. Mats of algae
and stews of bacteria seemed to be all that was possible for quite a
long time indeed.
The secret ingredient appears to have been sex. Asexual reproduction,
in addition to being rather boring, doesn't introduce anywhere
near the
possibility for diversification of a genome like sex does. So
somewhere
around 700 to 1000 million years ago, life discovered this new way to
do things, and that seems to have been the real turning point.
David Brin on 1999-05-24 said:
Evidence from meteorites is strong that there was a
differentiated body that got broken up ~600 million years ago,
and that that's what many asteroids may be from. If so, you
don't have to drill at all: you just find the right asteroid and
harvest the whole thing.*
* Some suggest this was one of 3 bits of evidence that the
solar system was visited in that time frame. The other two were
the Cambrian "explosion" of life ("somebody flushed a toilet"),
and the claim that the age-distribution of ore-bodies of certain
minerals that might be of interest to advanced civilizations
shows a distinct drop for ages >600 million years.
Of course, the "somebody flushed a toilet" idea is ludicrous.
Somebody made a deposit is more like it... Some exceedingly patient
interstellar race, hoping to get a jump on the whole uplift thing that
was just getting started, visited an off-short bank (Earth) and
deposited a whole lot of genetic material, knowing that it would accrue
interest over the eons. In 1947, passbook in hand, ready to make a
withdrawal. There was some kind of accident in the parking lot, and the
rest, as we know, is history.
Dave
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