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Re: Europa Dope



Ahhh, but in order to make such a claim, you *must* assume that there is
more than one possible biochemical pathway for carbon-based life to form.

Why shouldn't I? From a chemical point of view it all looks like a small random selection from a tremendous wealth of possibilities. For example, who needs both leucine and isoleucine, or why do some 800 amino acids occur in some organisms, but at most 22 are encoded in any genome? Why aren't there any pyridine bases which could form metalloribozymes or even -deoxyribozymes? Why this rather unstable sugar-phosphate backbone instead of, say, one formed of peptide bonds? (Artificial "PNA" has been produced and is used for certain biochemical experiments.) Why are cell membranes of non-archaeans made of both phosphate-glycerol-fatty acid molecules and sphingosines (which mimic the shape but not the chemical properties)? Last but not least, why is there so much homology across all life? Why is the tubulin in our cytoskeletons such a plausible homologue of the FtsZ that bacteria and archaea use for cell division, to use an example that is not immediately obvious?