Fig 4. Evolutionary dynamics of the density of cooperative nodes over time.

We show the fraction of cooperative nodes ρ_i against the rounds or time steps (t) before feedback (a) and after the first feedback round (b), the second feedback round (c) and the third feedback round (d). ρ ranges in [0, 1], where 0 corresponds to the global defection, while 1 means a global cooperation of population. We simulated the evolutionary dynamics of the ISG for a fixed number of simulations, and the color, ranging from ‘blue’ to ‘red’, corresponds to the density ρ_i. We can observe a fluctuation in strategies determined by the feedback rounds from gut acting alternatively as incentives towards cooperativeness (see (b)) and a coexistence of the two strategies, with more defectors than cooperators (see (a), (c) and (d)).