On the emergence of large-scale human social integration and its antecedents in primates

One of the universal features of human sociality is the fact that our social networks are highly integrated – human societies exhibit several nested social layers including families, bands and communities. Several factors have been identified as creating disincentives for hostile intergroup relations, including economic interdependence (trade), intermarriage (exogamy), cooperative defence against external adversaries (warfare), and lack of patrilocal residential groups (absence of patrilocality with external war). We provide a preliminary test of hypotheses relating to the correlates of amicable relations between communities (i.e. absence of internal war) using the standard cross-cultural sample (SCCS) database. Intermarriage did not have any explanatory power, there is a nearly significant effect of trade on the establishment of intergroup tolerance, and the evidential basis for cooperative defence and patrilocal residence are strong when combed into a multiplicative effect. This analysis is complemented with an exploration of the evolutionary factors underlying elementary forms of meta-group organization in non-human primates.