Final answer:
The most important affiliative behavior among non-human primates is grooming.
Step-by-step explanation:
The most important affiliative behavior among non-human primates is grooming. Grooming is a social behavior in which one primate picks through the fur of another, removing dirt, parasites, and loose hair. It serves as a form of bonding and social interaction among group members. Grooming helps to maintain social cohesion, reduce tension, and establish social hierarchy within the group. For example, activities such as grooming, touching the shoulder or root of the tail, embracing, lip contact, and greeting ceremonies have all been observed in the Indian langur, an Old World monkey.