  We investigate the evolution of populations of random Boolean networks under
selection for robustness of the dynamics with respect to the perturbation of
the state of a node. The fitness landscape contains a huge plateau of maximum
fitness that spans the entire network space. When selection is so strong that
it dominates over drift, the evolutionary process is accompanied by a slow
increase in the mean connectivity and a slow decrease in the mean fitness.
Populations evolved with higher mutation rates show a higher robustness under
mutations. This means that even though all the evolved populations exist close
to the plateau of maximum fitness, they end up in different regions of network
space.
