Fitness evolution. The change over generations in average fitness of population, and the fitness of the best SCFG. Here, a lower fitness is more desirable, the SCFG predicting better secondary structure. Many improvements to both the whole population and best SCFG are made in the first 100 or so generations. After this, the best SCFG does not become much better, but the average population fitness continues to fluctuate. Clearly the algorithm continues to explore alternative SCFGs and tries to escape the local optimum.