In group-living animals, sociality maybe impacted by both ancestral relationships, and current socioecological factors. Assessing their relative/dynamic effects on the evolution of diverse social systems has been a major challenge for researchers. I present aspects of my research that focus on examining the impact of phylogenetic relatedness, group-size and resource-competition, and most recently human impact, on nonhuman primate social structure and/or zoonotic infection risk. In this regard, macaques (genus: Macaca) are an ideal genus, with their similar social organizations and well-established phylogenies, but diverse (despotic-to-tolerant) social styles, geographic ranges, and degrees of overlap with human landscapes. First, I use a comparative approach to reveal that the structure of
dominance relationships across macaques show strong phylogenetic signals, i.e. members of the Sulawesi lineage show more shallow hierarchies and less transitivity/certainty in their dominance networks than those of the Arctoides and/or Fascicularis lineages. In contrast, grooming network structure seems more labile to the influence of group-size, with larger groups showing more modular, less dense network connections than smaller groups. Second, I describe contrasting evidence that sociodemographic factors impact within-species differences in macaque sociality. Among free-ranging rhesus macaques, larger group-size and/or intense resource-competition appear to generate greater degrees of despotism, i.e. more asymmetry in dominance and lower rates of post-conflict
affiliation. However, among wild Tibetan macaques, larger group-size/severe rangerestriction appeared to lower degrees of despotism, i.e. shallow dominance hierarchies and greater reciprocity in grooming on account of a decreased demand for rank-related benefits such as support in conflicts. Thus some aspects of social behavior maybe linked to ancestry, whereas others are labile to socioecological and/or supply-and-demand biological markets conditions. My current research is implementing the conceptual framework of coupled-natural-and-human-systems to assess the impact of anthropogenic
factors on variation in macaque social networks and susceptibility to zoonotic bacterial pathogens. Further, work on captive rhesus macaques is revealing that increased social network connections may either socially buffer individuals from microbial infection risk, or enhance such risk owing to contact-mediated sharing/transmission of microbes. This may depend on pathogen-specific modes of transmission and/or overall social context. This naturally sets the stage for future investigations of the socioecological bases of zoonotic infection/ transmission through networks of free-living primate populations. I
end by conceptualization group social structure as social reaction-norms, i.e. where groups may respond similarly to variation in extrinsic factors, but may have inherently different ranges of responses to the same conditions.