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Politics : Should God be replaced? -- Ignore unavailable to you. Want to Upgrade?

To: TigerPaw who wrote (17602)	6/2/2004 11:37:06 AM
From: Solon	Read Replies (1) \| Respond to of 28931

There is endless speculation as to how it started and what it is! But most of us just need to figure what to do with it! "...A radical view has been advanced by Cairns-Smith and more recently by Greg Retallack in which clays are more than sites of concentration of organic molecules but are, in fact, the basis of original life (though no as we knowit, being Si rather than C based). According to these writers, protein rich C based life is a recent innovation and that prior to the carbon tale over life was mineral-based. These notions are based on a definition of "life" which stresses reproducibility and a capacity to evolve, both of which are exhibited to some degree by clay particles. Clays are capable of catalysing complex reactions, can be templates for the assembly of molecules, concentrate organic molecules and compartmentalise reactions. All of theses properties, as noted by the less radical "mineral life" faction can improve the probability that organic molecules will combine in novel ways and become "living" things. Implications Whatever the origin of the first living things, they were most certainly scavenging heterotrophs of som stripe, using simple abiotically synthesised molecules as "food". Powerful selective pressures would have built rapidly as consumption began to exceed supply. When active respiration became the norm, atmospheric composition began to change in sympathy, particularly when photosynthesis put in an appearence. This can be clearly seen in the gochemical record. the very earliest iron enriched minerals are all reduced, implying an absence of free oxygen in the system at the time. From about 3.8 Ga to about 1.7 Ga, iron rich sediments are typically banded iron formations, Si rich iron deposits which scavenged free oxygen form the atmosphere, keeping it in an anoxic, reducing state until such time that the capacity of Fe to soak up oxygen was saturated and oxidised red beds became the norm. This seems to have occurred after about 1.7 Ga and spelled the end for the rich Archaean biotas of anaeobes. They now survive in extreme, anoxic environments such as salt lakes, sewer pipes, deep ocean vents and the guts of ruminants where they provide a window into our distant evolutionary past. From the time photosynthesis began to oxygenate the atmosphere and living things evolved physiological methods of exploiting the previously toxic oxic environment, the possibilities of futher spntaneous generation of life were snuffed out and long term survuval on Earth became absolutely dependent on the capacity of the newly rampant primary producers was absolute. From an evolutionary point of view, the solutions reached at molecular, genetic and structural levels for coping with an oxygenated atmosphere effectively set the scene for all subsequent events - everything that followed were, in this sense, variations on an ancient theme with little room for fundamantal innovation. We still pay the price through the inefficiency of photosynthesis, the importance of antioxidants to wellbeing and, probably through many of the physiological challenges underlying aging, senescence and death..." tesag.jcu.edu.au