1. Chapter 7: Play and aggression Thesis of chapter: That NS favored restrained aggression in humans and rough-and-tumble play was critical to this selection process.

2. Restrained aggression and rt play Observational evidence: Lethal aggression among conspecifics is rare in animal world, displays and ritual aggression are more the norm Lethal aggression varies, but is not common among nomadic foragers and is usually for personal, not collective reasons Evidence from animals and human children indicates that rt play serves as a venue for development of social skills, assessment of an opponent’s strength, sensitivity to dominance/submission cues and restraint in aggression.

3. (Non-predatory) Aggression among animals rarely “fight to the death” Why not: all out aggression is costly, even the eventually winner may suffer debilitating fitness- threatening injuries. Better for the winner to save energy and loser to live to fight another day. Display: Non-contact signals of intent and quality. Ex: roaring contests among lions or deer. Displays out number aggression 60:1 among elephant seals. Ritual contest: stylized fighting with implicit rules. Ex: heat butting among big-horn sheep; antler wrestling among caribou.

4. Chimpanzees Note: not mentioned by author but among closest human relatives – chimpanzees both display and fight, fights can sometimes be quite violent and occasionally lethal. They display more and ritualized gestures of dominance and submission serve to regulate fights.

5. Aggression in the EEA Reconstruct the EEA by looking for recurring patterns in nomadic hunter- gatherers Violence in nhgs: (1) avenging death of family member, (2) males fighting over females, (3) collective violence against a “bad” group member. Non-violent dispute resolution: (1) leaving group either collectively or singly; (2) avoidance; (3) gossip or ostracism; (4) group meetings, (5) ritualized contests

6. Dealing with out-groups Avoidance trade gift-giving. Since nhg own very little are highly mobile they almost never fight over land, resources, possession – most common things people fight over today. Thus, little if any organized, militaristic fighting or warfare.

7. Display and contest among nomadic hg’s Verbal abuse: sitting around campfire; drum matches; Contests: wrestling matches, exchange of blows; ordeal rituals In most cases winning a contest fairly enhances status, cheating leads to ridicule, shame. Factors militating against too much aggression among h-gs: (1) strong need for cooperation; (2) presence of kin within groups (inclusive fitness); (3) severe risks of being outcast; (4) revenge ethic

8. Role of R-T play in restrained aggression Common among larger-brained social animals, especially mammals and primates Universal among healthy, typically-developing children including h-g children Undoubtedly would have been present among children in our ancestral past

9. Role of R-T play in restrained aggression Two assertions regarding r-t play and aggression In children: it plays an important role in learning restraint in aggression In adolescents: important for learning rule-based contest nature of aggression

10. Evidence Lack of rt play has been associated with poor social skills and inability to distinguish play from real aggression Rats raised without rt play over- reacted to benign social contact, treated it as an attack Male mice raised only by females or monkeys raised without conspecific interaction both showed heightened aggressive reactivity Human children increased rt play associated with social competency

11. Evidence Shift in rt function with age – younger children: practice function for physical skills; older children: dominance function in determining strength and social status. In older boys: rt can vary in seriousness as play sessions progress, serious until submissive act, then play resumes, suggesting a restrained way of determining social status. Intermingling of serious aggression and play fighting in older boys (mostly) parallels h-g contests where serious matters are handled with rules and restraint, not all out aggression