grouping of OMUs who routinely sleep and forage together. The troop is a temporary aggregation of bands who might also forage or sleep in the same sites depending on environmental constraints. While multilevel societies might seem similar to fission fusion societies, they are not. Fission fusion societies have a dynamic element with routine variability whereas multilevel societies maintain stability through the hierarchy of core units. In order to fully understand how these complex societies function, it is important to observe social relationships and their interactions not only within tiers, but between them as well. Modular systems are considered to be an evolutionary construct resulting from the need to split up larger groups, whether they are large multi-male-multi-female groups or an amalgamation of closely related units. Examples of primate species with multilevel societies: hamadryas baboons, geladas, snub-nosed monkeys Primate social structures Primate social structures are meant to describe the diverse relationships that exist between individuals, as well as the patterns of interactions that define them. Researchers hypothesize that environmental and social pressures have allowed for a whole array of inter-individual (between individuals) relationships that promote inclusive group fitness. Inter-individual relationships are thought to be influenced by sex-related variables and can occur (1) between females, (2) between males or (3) between members of the opposite sex. Factors influencing inter-female relationships are primarily thought to be: food competition; group size; and dispersal patterns. These three elements will characterize the degree of competition among female group members. For instance, in a female philopatric society there are often stable kin-based hierarchies that develop. Conversely, in male philopatric species or egalitarian societies, females regularly transfer between groups (eliminating the potential for hierarchies or coalitions) leading to female bonding as a sole mechanism for resource defence against other groups. Inter-male relationships tend to be characterized by agonism and competition over access to females. Socioecological theory predicts that fierce competition exists among male group members over access to females, leading to higher frequencies of agonistic interactions being common. Some species of primates demonstrate male-male relationships leading to alliances and affiliative behaviors when inclusive group fitness is being prioritized over individual fitness. Finally, intersexual relationships (between adult male and adult female individuals) are also shaped by a number of factors, including sexual selection, dispersal patterns, dominance structures, certainty of paternity, risk of infanticide and/or the level of sexual dimorphism that is present within a species. Affinity and affiliation between