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© 2015, Springer International Publishing. The human kinship system, and its associated terminology, bears the hallmarks of an evolutionary adaptation but its evolutionary origins have not been explored. We argue that the human kinship naming system is a schema that evolved to reduce the cognitive load of maintaining kinships, allowing the expansion of the human network and an increase in survival. We report on the results of two response time studies, using moral dilemmas as a proxy for relationship maintenance, which test the hypothesis. We find qualified support for our argument. Within the 50 layer of the social network kinships do impose less cognitive load than friendships allowing a saving in processing power and an increase in social network size beyond that seen in non-human primates. However, the result in the 150 layer is contrary to that posited by our hypothesis: kinships impose a greater load than friendships and this load is highest when refusing help to kin. We explore and discuss the influence on results within this outermost layer of the nature of response, the influence of the wider network and the temporal distance which exists between ego and alter at this level of the network.

Original publication




Journal article


Adaptive Human Behavior and Physiology

Publication Date





195 - 219