An alternative hypothesis would suggest evolutionary minimization of errors or optimization of the distances between the properties of amino acids and of triplets. The mechanism suggested by this hypothesis is that various distributions of attributions once existed, produced by point mutations that changed slightly the triplet character. When this change would code for an amino acid with properties very different from the original attribution, such coding would be strongly selected against. The end result of this process would be the observed regionalization of the attributions, so that similar amino acids would be attributed to similar codes and the changes produced by point mutations usually would not change drastically the amino acid character. The only tests possible of this hypothesis are simulations of the evolutionary process, and they do show that the present distribution of attributions is among the best for minimization of errors (Knight et al., 1999). Otherwise, the hypothesis does not refer to mechanisms of origins of the attributions.
We propose that both catalyst-driven and selective optimization hypotheses are complementary and refer to different aspects or moments of formation of the code. Our attempt is to maximize biochemical mechanistic explanations and to reduce the more vague propositions of natural selection, based only in the considerations that the present state of the system is optimized, and that other variants once existed but tended to produce worse products (phenotypes) and were selected out. The outlier attributions are considered the earliest to be fixed, based on the premise that the catalysts responsible for them had properties different from the ones that produced the correlated attributions.
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