offtopic: Fermi Paradox, evolutionary filters, and life on Mars

From: Mitchell Porter (
Date: Sun Mar 25 2001 - 05:55:46 MST

--- Brian Atkins <> wrote:
> If there is no detectable intelligent life besides
> us in this galaxy, and
> apparently no where it could have gone (other
> universes, etc.), that makes
> me strongly believe we are in a simulation. But on
> the other hand the
> increasing evidence of dead life on Mars would seem
> to point the other
> way... in which case- where the heck are they?

Remember the concept that technological intelligence
requires passage through a number of evolutionary
filters. First you have to have life, then
intelligent life, then starfaring life, and only
in the last case is the Fermi Paradox a problem;
and if only one planet in a million makes it through
each of those filters, then there could be 10^18
planets in Earth's past light-cone, without it
being unlikely that we're the first spacefaring
intelligent species in this part of the universe.

Now you might say that if Mars had life, that's
evidence against the idea that biogenesis is a
1-in-a-million filter - since here's another
planet that made it through, right next door!
But Earth and Mars are similar enough in
composition, history, and astrophysical environment
that if one has the ingredients for life right,
the other can't be too far away; and it's also
very possible that life on one originated on
the other. Paul Davies has a scenario in which
the first lifeforms are nanobacteria which evolved
in the Martian crust, were brought to Earth by
ejecta from early-solar-system meteoritic
bombardment of Mars, and which evolved on Earth
into thermophile archaebacteria, which molecular
phylogeny places at the bottom of our tree of life.

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