Jessica Flack, David Krakauer of the Santa Fe Institute and colleagues discovered that monkey has a complex "voting" system to appoint monkey cops to police their group.
Once elected, police monkeys earn certain rights and responsibilities, one of which is to peacefully settles conflicts. They usually do this by stepping between combatants or chasing bad monkeys away. Very rarely do they need to dish out a whooping, but their actions are always respected by the group.
When Krakauer and his colleagues removed the police force—which in this case consisted of three males, but can also include females—they saw a drastic change in a once peaceful, interactive society.