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"