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Figure 1 Joint evolution of a direct character, , that reduces the sensitivity of the direct character to perturbations.

Figure 1. Joint evolution of a direct character, δ, that filters signal from noise, and a buffering character, τ, that reduces the sensitivity of the direct character to perturbations.

The intensity of perturbations rises with the cost of incorrect signals, b. The direct character has an independent cost, c. (A–C) The optimal value of the buffering character, τ*, when both the buffering character and the direct character evolve freely. (D–F) The optimal value of the direct character. The solid line shows δ*, when both the direct and buffering character evolve freely. The dashed line shows , the evolutionary response of the direct character when the buffering character is constrained to , as explained in the text. (G–I) The ratio of fitness, w, when both characters evolve freely to {δ*,τ*} relative to when τ is fixed and δ evolves freely to the point . The ratio shows the net benefit of robustness in terms of enhanced fitness from buffering against perturbations.