Final answer:
Large coalitions among humans and primates can struggle with cooperation and cohesiveness due to free-riding and collective action problems; whereas small groups have stronger internal cohesiveness but may lack influence.
Step-by-step explanation:
Among humans and non-human primates, if coalitions get too large, the members tend to find cooperation difficult to achieve. In larger groups, individuals may not trust or even know each other, and the risk of free riding increases. The larger the group, the more susceptible it is to a lack of cohesion and to the challenges of collective action problems, such as tragedies of the commons or prisoner's dilemmas, which are more difficult to manage than in small groups. As the group grows, it may gain attention and the ability to exert more pressure toward a shared goal, but simultaneously, the potential for division and internal conflict also rises.
Small groups, on the other hand, generally benefit from stronger internal cohesiveness and shared connection, with individuals more likely to notice and address any free-riding behavior. However, these small groups can struggle to exert influence when up against larger collectives. As populations grow and group sizes increase, individuals encounter more people outside their personal in-group, further complicating the dynamics of group behavior and action.