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Politics : Evolution -- Ignore unavailable to you. Want to Upgrade?

To: Solon who wrote (9773)	11/12/2010 12:12:17 PM
From: Brumar89	Read Replies (3) \| Respond to of 69300

All life having the same genetic code IS an argument for common ancestry of life on earth. Not proof but a reasonable argument. OTOH all life having the same genetic code is also a strong argument against the idea that genetic codes could have spontaneously generated and evolved. If they could, we'd see millions of genetic codes in different living things, just like we see vastly different genomes in various species. BTW despite what the folks at oxfordjournals say, there's NO evidence of genetic code evolution or "expansion" just a surmise. ---------------------------------------------------- The evolutionary forces that produced the canonical genetic code before the last universal ancestor remain obscure. <We don't have the slightest idea but it must have been evolution cause we believe there's nothing else. So much for the idea that evolution isn't used to explain the origin of life btw.> The arrangement of amino acid assignments to the codons of the standard genetic code appears to be a direct product of natural selection for a system that minimizes the phenotypic impact of genetic error. <The genetic code's design does minimize errors so we're going to say natural selection made it that way. Because intentional design is out of the question.> While the evidence for an adaptive code is clear, the process by which the code achieved this optimization requires further attention. <Since it's optimized it must be a product of evolutionary adaption. Use that assumption and then it's clear.> -------------------------------------- Re. their conclusions, they haven't actually provided ANY evidence the code is a product of natural selection. Since its optimized, it "meets .. the predictions of the adaptive hypothesis". That's it. Yes, if genetic codes could evolve, an optimized code would be consistent with evolutionary adaptation. I like that they actually use the word "hypothesis" though, and that they explicitly said the genetic code's codon assignments "cannot be explained as an artifact of stereochemistry". ---------------------------------------------------- None of this is new. Francis Crick realized decades ago that evolution of a genetic code was unlikely at best. The problem with code evolution is the code is carried within living organisms whose existence depends on the code. Start changing it and the organism doesn't work. Everything that depends on the code would have to change at once as the code changed. A logical impossibility. Being an atheist, Crick hypothesized that life was seeded on the early earth by extraterrestial civilizations.