Fig. 2.

(A) Average fitness $⟨F⟩$ versus evolution temperature $T_e$ for various system sizes where $z=5.0$. A steep change in fitness is seen near $T_c\approx 0.09$ for relatively large systems. (B) Specific heat $c$ versus temperature $T_e$. The maximal specific heat increases with the system size $L$, suggesting the existence of a transition at some $T_c$. (C) Fitness averaged over local maxima ${⟨F⟩}_{T_e=0}$ versus coordination number $z$ in log-linear scale. The black line shows the fitness if no mechanical response is present at the active sites. (D) Entropy density $S/N$ versus temperature $T_e$. The entropy jump near $T_c$ indicates the number of degrees of freedom that must be tuned to achieve the desired response.