the multi-male-multi-female system. For instance, one study of savannah baboons (Papio cynocephalusI) observed that the lactating females in the group would more closely associate with specific adult males. As further research is conducted on primate friendships, three main benefits have been hypothesised: close associations with a specific male (1) tends to discourage infanticide, (2) tends to reduce incidence of harassment of the female, and (3) stimulates paternal investment and care in the offspring. The benefits of friendships within the multi-male-multi-female group systems demonstrate similar advantages as pair-bonded systems. Examples of multi-male-multi-female structured primate species: many species of macaques, baboons, vervet monkeys, mangabeys, capuchins, squirrel monkeys, woolly monkeys, some colobine species, some lemurs (ring-tailed and sifaka). Fission fusion societies demonstrate a high degree of fluidity by splitting (fission) and merging (fusion) as the group moves across a landscape. This type of organisation is less cohesive than multi-male-multi-female groups, with patterns often reflecting the local availability of resources. For instance, if foraging patch sizes are small, the larger group will often break apart to forage and later merge in order to sleep. This type of society is typically characterised by female philopatry, where female kin lineages make up the core of the groups and males disperse to other groups. Interestingly, some researchers hypothesise that fission fusion societies may have been socially inherited from the last shared common ancestor of humans, chimpanzees and bonobos. Examples of primate species with fission fusion societies: humans, chimpanzees, bonobos, spider monkeys Multilevel societies, sometimes referred to as hierarchical or modular societies, are the largest and most complex form of primate social organisation. Social stratification of these societies is discrete and has at least one stable core unit. Typically, multilevel societies are composed of between two and four levels of social structures: one-male units (OMUs, or harems) nested within clans, which are nested within bands, which are nested within a troop. OMUs are composed of a single-male breeding unit (a leader male), several females, and may even have a follower male. Similar to the resident male of a one-male-multi-female group, the OMU leader male is susceptible to takeovers by outside adult males. In some species, there is an additional level to the society: clans. The clan level is nested between the OMU and the band level. Clans consist of OMUs and of all-male units (AMUs) of bachelor males (either kin-related or not). Finally, a band is a coalesced