Figure 5.

Hunting returns with and without the presence of one or more young (less than 20 years old) cooperative foraging group members (a) or younger ‘assistants’ (b). Lines represent predicted means based on multilevel models (see the electronic supplementary material for details). Statistical assessment for differences between groups in both panels are reported in the text. Note that panels (a) and (b) have different x-axes because there were no observations of assistants accompanying hunters older than 73 years. (Online version in colour.)