Figure 4. Evolution of expression dynamics toward cooperative adaptive responses.

Temporal changes in the expression levels of all genes in the network with the largest fitness value for a generation in each stage: (a) 10th, (b) 80th, and (c) 1,000th generation for and . An shift was added at . The response of the target gene is shown with a bold black line. The expression levels of target-activating genes are shown with dotted red lines, those of target-inhibiting genes are shown with dashed blue lines, and genes having no interactions with the target are shown with thin straight gray lines. The plateau in the maximum response of the target is commonly observed in networks with large average adaptiveness, albeit it is not requested by the fitness function itself. Note the differences in scales of time (abscissa). (a) fitness, ; (b) fitness, ; (c) fitness, .