when the two RNA molecules were allowed to replicate and evolve in the presence of not one, but five different substrates, the two RNAs were able to coexist, but in an unexpected way. Initially the two RNA molecules utilized all five substrates in varying degrees in order to replicate. After all, all five were present and therefore all five could be utilized to some extent. But here is the punch line: over time each RNA molecule evolved so as to optimize its replicative ability with respect to different substrates.
