Figure 1.

Schematic of Spiegelman’s experiment. Test tubes contain Qβ replicases (grey globules) and activated mononucleotides (red letters). RNA molecules (blue ladders, branched or non-branched) are inoculated at the start of an experiment and serially transferred. RNA molecules evolve faster replication and shorter lengths. (Adapted from Eigen et al. [9]. The original figure, however, depicts RNA molecules evolving longer lengths in opposition to what actually happened in Spiegelman’s experiment.) (Online version in colour.)