Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!ll-xn!husc6!husc4!chiaraviglio From: chiaraviglio@husc4.HARVARD.EDU (lucius) Newsgroups: sci.bio Subject: Re: Non-carbon based life Message-ID: <2638@husc6.UUCP> Date: Mon, 3-Aug-87 13:19:45 EDT Article-I.D.: husc6.2638 Posted: Mon Aug 3 13:19:45 1987 Date-Received: Tue, 4-Aug-87 04:00:13 EDT References: <265@askja.UUCP> Sender: news@husc6.UUCP Reply-To: lucius%tardis.harvard.edu@harvard.harvard.edu (lucius) Distribution: world Organization: Harvard Graduate Lines: 50 Keywords: Crystalloform life Summary: Check out by A. G. Cairns-Smith In article <265@askja.UUCP> frisk@askja.UUCP (Fridrik Skulason) writes: >As everybody knows, all life - as we know it - is carbon based. Now, what >I would like to ask is: > > Is non-carbon based life possible? > >In other words - is it possible that life could evolve on a planet where no >carbon existed ? Actually, the first question is the more general one. A. G. Cairn-Smith's intellectual exercise (in the book listed in the summary field of this article) suggests very strongly that the answer is yes. He postulates that life on Earth actually began as inorganic crystalline life which evolved to use organic molecules. Gradually the organic molecules began to store information, and eventually the original crystal structure became superfluous and was discarded. His argument is that such thing as self-replicating RNA molecules are too complicated *and* require too much energy to make (so that they are too unstable) for them to be formed without pre-existing life, whereas this limitation does not apply to self-replicating crystals. Crystals are capable of preserving and replicating information under the appropiate conditions (which are not as stringent, and closer to the conditions thought to exist on the primordial Earth), and can catalyze reactions; both features are needed for chemical life. >Silicon-based creatures appear in quite a few SF stories, but is it really >possible to obtain the necessary complexity without carbon ? Most people talking of silicon life (including in SF) make the mistake of simply substituting silicon for carbon. This doesn't work very well, because polysilanes are much less stable than hydrocarbons, and therefore silicon analogs of many carbon compounds could not exist or would be too unstable to use as structural compounds of life. However, life based on polysilicates (an entirely different kind of molecule) might be possible. . . This is the kind of material (actually things like silicoaluminates and other such minerals) that A. G. Cairns-Smith suggests might have made up the first life. >I am not sure if this question can be answered at all, or if one first has >to answer the following question: > > What is life? I would answer this, but the fact that I can post this message even is probably a fluke, and I had better finish up before this bad ARPAnet connection flakes out and loses all of it. Maybe in a later message. -- Lucius Chiaraviglio lucius%tardis@harvard.harvard.edu seismo!tardis.harvard.edu!lucius