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Originally Posted by Huevos Grandes
most complex lifeforms on Earth do not build 20 amino acids (this is one of the reasons I eat food).
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Absolutely; humans are heterotrophic and need to eat protein to survive.
I was refering to the biology of Earth as a whole, which is remarkably consistent in it's amino acid make-up; but it may well have evolved from a small number of instances of abiogenesis- possibly just one.
You are no doubt more familiar with the twenty amino acids coded for in DNA/RNA than I am, but here they are anyway;
http://users.rcn.com/jkimball.ma.ult.../C/Codons.html
My suggestion is that other possible associations of more exotic acids don't get a chance because these twenty and their derivatives out-compete them; and they can do this because of their association with DNA/RNA.
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Originally Posted by Huevos Grandes
And while I am unable to disprove your assertion, I will say that complex life can only form where DNA/RNA (other some other stable information-carrying molecule) self-replicates.
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Do you think it possible then that other stable information-carrying molecules might exist? Any suggestions? If such molecules do exist they might not code for a biology using all the same amino acids as our own.
Or, alternatively, other information carrying molecules might code for a biology remarkably similar to our own. It is certainly possible that the association of proteins and amino acids that we have on Earth is the simplest and most optimised for survival;
but we have only a sample of one to go on.
If all life on Earth descends from a very small initial sample, then the common features might be a result of that limited ancestry rather than a universal rule.