From: Robert J. Bradbury (bradbury@www.aeiveos.com)
Date: Sat Sep 11 1999 - 10:39:15 MDT
On Sat, 11 Sep 1999 hal@finney.org wrote:
>
> But actually assembling some kind of self-replicating
> system or cycle is still not well understood.
Given that we get a stable crust ~4 billion years ago and life seems
to appear at 3.86 billion years ago, that says that (a) it either
came from space (panspermia); or (b) it is easy.
>
> There is still a very hard step here, going from the building blocks
> to self-replication.
If it came from space, then it is (a) ubiquitous; or (b) we are a
very special case.
> Until we have come up with some convincing way to bridge this gap
> I don't think we can say that scientific evidence suggests that
> life is likely to be common.
>
What we really need to know is the relative sizes of the
life "phase space" and the non-life "phase space". It would
appear, given the millions of compounds that can be made
out of C/H/N/O (some of the most aboundant elements), that
the phase space for fundamental building blocks (amino
acids, RNA, etc.) is large. Since scientists have come
up with scenarios for other information carriers (I think
for example peptide nucleic acids), we may be based on
a "difficult" to evolve information carrier, but that
doesn't imply that other life forms must be.
You may want to look up: "The orgin of life--a review of
facts and speculations", by L. E. Orgel, Trends Biochem Sci.
Dec 1998 23(12):491-5.
Robert
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