individuals is often largely determined by the dispersal patterns characterizing a primate social system. For instance, chimpanzees (Pan troglodytes) have patrilineal social systems, where the males usually remain in their natal groups and the females emigrate into neighboring groups. Conversely, in the matrilineal societies of bonobos (Pan paniscus), it is the females who remain in their natal groups and the males who disperse to new groups. Dispersal patterns will also likely affect the structure or organization of social hierarchies. There are also affiliative behaviors which encourage stronger associations among individuals over time. Close proximity, grooming and non-aggressive social interactions are expected characteristics of well-bonded primates. Grooming is a multifunctional behavior. Firstly, it is practical. Grooming allows the opportunity for unwanted dirt, dead skin, debris or ectoparasites to be removed from an individual's hair or fur. Moreover, it is a social activity. Grooming helps initiate new relationships and maintain existing ones; it can be used to deflate aggressive social interactions; and, it is beneficial to an individual's health since grooming has been linked to reductions in stress. Agonistic interactions, or agonism, refers to the frequency and degree of aggressive and submissive interactions occurring between individuals. The frequency at which individuals are being subjected to agonistic interactions could be related to factors such as rank (there is evidence of both high- and low-ranking individuals being targets of conspecific harassment) or dispersal patterns (non-resident individuals attempting to emigrate into other groups can often be at higher-risk of harassment from resident group members). Primate social systems and their organisation exist across a spectrum. While some systems reflect a strict dominance hierarchy, others are characterised by more egalitarian structures. A confluence of variables and behaviours, such as diet or dispersal patterns, are thought to shape social systems. Many forms of social hierarchies exist in primate systems. In resident-nepotistic intolerant hierarchies, the stable hierarchy is based on kinship and rank can be linearly traced, as it is inherited. In contrast, in resident-nepotistic-tolerant hierarchies, stability is maintained via inter-individual coalitions and tolerance by dominant individuals. In this system, power is not ultimate; it is partially mitigated by cooperation among subordinate individuals. Another form of dominance structure is related to age. For example, some gorillas demonstrate an age-graded dominance structure: wherein the eldest male member is the highest-ranking dominant male (or alpha). Primate mating systems Primate mating systems infer both a social element and a genetic element. Therefore,