Coalitional Play Fighting and the Evolution of Coalitional Intergroup Aggression.

Dyadic play fighting occurs in many species, but only humans are known to engage in coalitional play fighting. Dyadic play fighting is hypothesized to build motor skills involved in actual dyadic fighting; thus, coalitional play fighting may build skills involved in actual coalitional fighting, operationalized as forager lethal raiding. If human psychology includes a motivational component that encourages engagement in this type of play, evidence of this play in forager societies is necessary to determine that it is not an artifact of agricultural or industrial conditions. We examine whether coalitional play fighting appears in the hunter-gatherer record and includes motor skills used in lethal raiding. Using the ethnographic record, we generated a list of motor patterns regularly used in forager warfare. Then, using Murdock's Ethnographic Atlas, we identified 100 culture clusters containing forager societies and searched the ethnographic records of these societies for descriptions of coalitional play fighting, operationalized as contact games played in teams. Resulting games were coded for the presence of eight motor patterns regularly used in forager lethal raiding. Although play does not tend to be systematically documented in the hunter-gatherer literature, sufficiently detailed descriptions of coalitional play were found for 46 of the 100 culture clusters: all 46 exhibited coalitional play using at least one of the predicted motor patterns; 39 exhibited coalitional play using four or more of the eight predicted motor patterns. These results provide evidence that coalitional play fighting (a) occurs across a diverse range of hunter-gatherer cultures and habitats, (b) regularly recruits motor patterns used in lethal raiding, and (c) is not an artifact of agricultural or industrial life. This is a first step in a new line of research on whether human male psychology includes motivations to engage in play that develops the deployment of coordinated coalitional action involving key motor patterns used in lethal raiding.