Conservation
Evolution is continually propelled by the past, always modifying its own context and creating the conditions for new steps. This dependence on the past makes the process highly constrained by history. ~ English botanist Enrico Coen
Well over 3 BYA the global community of viruses had homogenized extant prokaryotes on a regime of DNA as the stable library for protein production, with RNA acting as librarian: the intermediate interpreter of DNA sequences. Genetic code used 20 amino acids, with ribosomes acting as protein factories via RNA construal.
Primordial prokaryotes had the machinery for metabolism and self-reproduction honed. Enzyme exploitation via cofactors was well in hand. Life was good.
Of the 548 metabolic enzymes found in E. coli bacteria, 50% are in all life forms. Only 13% are bacteria specific.
