Path: utzoo!attcan!uunet!peregrine!ccicpg!felix!dhw68k!feedme!doug
From: doug@feedme.UUCP (Doug Salot)
Newsgroups: sci.bio
Subject: Re: Evolution
Summary: the eight steps to life?
Keywords: evolution
Message-ID: <114@feedme.UUCP>
Date: 4 Jul 88 21:33:44 GMT
References: <5944@bloom-beacon.MIT.EDU> <112@feedme.UUCP> <5334@ecsvax.uncecs.edu>
Reply-To: doug@feedme.UUCP (Doug Salot)
Distribution: sci.bio
Organization: Feedme Microsystems, Orange County, CA
Lines: 59

Thanks to all who threw books at me for my question on what
selective forces may have contributed to prebiotic cellular
formation.  I was hoping for a quick summary of current
theory such as what I was able to generate from chapter 1 of
Molecular Biology of the Cell (1983, Alberts, Bray, Lewis, Raff,
Roberts and Watson):

1)	assume the ready availability of CO2, CH4, NH3 and H2
2)	amino acids, nucleotides, sugars, and fatty acids will
	be produced in aqueous solution when energy is supplied
	in the form of heat or u.v.
3)	polynucleotides and polypeptides will be formed by heating
	the dry organics or in the presence of polyphosphate catalysts
4)	polynucleotides "reproduce" by acting as templates for the
	polymerization reactions of their complements.  poly-
	merization can be sped up by the presence of minerals and
	metal ions (clay?)
5)	errors in replication will lead to new sequences

Enter selection:

6)	for suitably long polynucleotides, bases will be paired with
	with other bases within the polymer itself forming various
	folds and 3-d conformations
7)	some 3-d conformations will be unstable or lead to replication
	difficulties.  these will not survive (ie, reproduce)
8)	when the raw materials become limited, the nucleotide sequences
	which can be replicated with the greatest speed and accuracy
	will dominate

That's about as far as you can go with linear complexity.  After
this, you have to think about interactions within pools of polynucleotides,
polypeptides and other molecules big and small.  For products
formed by multiple-step processes to benefit the originating structures
by selection would require localization of everything involved along
all of the paths leading to the beneficial products.  Cell membranes
provide one level of localization and are formed pretty much spontaneously
from lipids in aqueous sol'n.

It seems clear to me that for evolution to continue on this scale
would require increasing orders of exponential time for each new
improvement.  I find it fascinating that "modules" with varying
degrees of functional independence evolved from these relatively
simple systems and that the modules can then compete on a new
level.  I wonder what the next level of organization beyond societies
will be.

Thinking about self-similarity and parallels between different
levels of evolution makes me wonder if anyone has proposed war-like
mechanisms at the sub-cellular scale.  If you consider the
development of certain protein-RNA complexes used for reproduction
catalysis as analogous to the development of tools for human
survival, is it likely that certain cells won primordial wars
by producing nucleases and proteases which digested competitors
much as humans use their tools to hunt other species?

-- 
Doug Salot || doug@feedme.UUCP || ...{trwrb,hplabs}!felix!dhw68k!feedme!doug
                    "Thinking: The Thinking Man's Sport"