The effects of population diversity were seen in Chapter 6 when studying code growth. The results showed how low fitness diversity reduces selection pressure and how high genetic diversity can reduce code growth. Chapter 7 showed how search using populations with a high number of equally fit and similar individuals is guided more by the dissimilar and poorly fit individuals. Chapter 5 demonstrated the increased exploration ability of more genetically dissimilar populations, but at the cost of fitness. Chapter 5 suggested population convergence can promote a hill-climbing behaviour that is beneficial to improving fitness on some problems.