Figure 4. Natural Selection for Viability Dramatically Increases Robustness.

The horizontal axis shows the number of genes per network. Black bars on the vertical axis show the mean mutational robustness R̄ _μ for populations under viability selection with PNμ ≫ 1, and grey bars show the mean mutational robustness R̄ _μ for a population with PNμ ≪ 1, in which selection for increased robustness is ineffective, and, thus, sampling of the metagraph is uniform (M ≈ 0.25 N², d = 0.5).