It is very likely that life began with some RNA (or RNA-like) molecules, self-replicating by base-pairing and exhibiting enzyme-like functions that favored the self-replication. Different functional molecules may have emerged by favoring their own self-replication at different aspects. Then, a direct route towards complexity/efficiency may have been through the coexistence/cooperation of these molecules.
Ma W, Hu J (2012) Computer Simulation on the Cooperation of Functional Molecules during the Early Stages of Evolution. PLoS ONE 7(4): e35454. doi:10.1371/journal.pone.0035454
Via Complexity Digest