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so the idea is that the actual LUCA is way further back, but the bacteria would keep updating themselves with the newest inventions, down to the codon table (which is universal apart from latecomer tryptophan, which deviates here and there UGG>UGA).

this is actual a vast open source eco system! there may have been different bacterial groups using different codon systems. but if you're sharing protein sequences, and your code is different, you'll build garbage. you get left behind and die out. *that*'s the reason everybody has the same code.