Some consequences of the RNA world hypothesis.

Entrez PubMed: "It is now generally accepted that our familiar biological world was preceded by an RNA world in which ribosome-catalyzed, nucleic-acid coded protein synthesis played no part. If the RNA world was the first biological world there is little that one can learn from biochemistry about prebiotic chemistry, except that the formation and polymerization of nucleotides were once prebiotic processes. If the RNA world was not the first biological world, the above conclusion may not be justified, and one can speculate that the monomers of earlier genetic polymers might be recognizable as important biochemicals. This suggests that the construction of replicating polymers from simple, not necessarily standard, aminoacids should be explored."
Orgel LE. Some consequences of the RNA world hypothesis. Orig Life Evol Biosph. 2003 Apr;33(2):211-8.