Fig. 2: Alternative outcomes of the coevolution of male and female negotiation strategies.

For 50 replicate simulations, the evolutionary trajectories of the heritable parameters \(({\alpha }_{m},{\beta }_{m})\) and \(({\alpha }_{f},{\beta }_{f})\) that determine the male and female negotiation strategies are shown in four panels where A \({\beta }_{m}\) is plotted against \({\alpha }_{m}\), B \({\beta }_{f}\) is plotted against \({\alpha }_{f}\), C \({\alpha }_{f}\) is plotted against \({\alpha }_{m}\), and D \({\beta }_{f}\) is plotted against \({\beta }_{m}\). All simulations were initialised at \({\alpha }_{m}={\alpha }_{f}=0.5\) and \({\beta }_{m}={\beta }_{f}=0.0\) and run for 40,000 seasons. The initial conditions correspond to a population where males and females provision their offspring at a constant rate of 0.5 and are indicated in the graphs by a black triangle. The evolved state of each simulation after 40,000 seasons is indicated by a solid dot. The 50 trajectories are representative for >1000 simulations we have run for our model: all converged to six different attractors, which in the panels are indicated by different colours. Each attractor corresponds to a different provisioning pattern (see Fig. 3): (P1) egalitarian biparental care (green), (P2a) male-biased care (purple), (P2b) female-biased care (pink), (P3a) male-only care (brown), (P3b) female-only care (yellow) and (P4) oscillatory care (blue).