Cohen, Ejsmond-Frey, Knight, & Dunbar (2010) Rowers high: behavioral synchrony is correlated with elevated pain threshold

The role of endorphins Physical exercise release of endorphins Psychological effects of endorphins? Release of endorphins social bonding Physical Exercise + X? heightened social bonding Synchrony

Rowers high Purpose: Will behavioral synchrony result in elevated release of endorphins?? Why rowers? Ergometeters (rowing machines)

Materials & Methods 12 male athletes (M = 24.25, SD = 3.769) Two week testing period Within-subjects design: Individual vs. Group Medisave Littman Classic II sphygmomanometer Blood pressure cuff Measured before and after training

Results Endorphin hypothesis (general) Pain threshold increased following exercise Ruling out alternative explanations No differences in work effort No carry-over effects

Results Group pain threshold changes were significantly elevated above those for individual trials

Discussion Synchronized activity heightens opioidergic activity Other evidence – runners ‘high’ Synchronous activities Wiltermuth & Heath, 2009

Power (1998) Old wives’ tales: the gossip hypothesis and the reliability of cheap signals

Dunbar’s ‘grooming and gossip’ hypothesis of language origins Vocal communication Adaptive response to increases in group size Replaced physical grooming More efficient Purpose: address problems with this theory

Coevolution of neocortex size, group size, and language Cost of group living Reproductive suppression Coalitions serve as a buffer against costs The neocortex ratio Social grooming (Dunbar, 1991) Evolution of larger groups A feedback process

Vocal grooming: the commitment problem Manual grooming: hard-to-fake currency Demonstrates commitment Cheney & Seyfarth (1990) Problems for vocal grooming hypothesis: Easy to fake Reduced commitment Does not produce natural opiates

Gossip: the reliability problem The ‘gossip’ hypothesis of language origins Rising group sizes Increased pressures on group cohesion New developments in vocal communication Problems for gossip hypothesis: Reliability Cheap signals Requires more energy expenditure

Contexts for gossip: male and female reproductive strategies

Male vs. female philopatry Ancestral human societies have been viewed as organized around male philopatry Evidence for female philopatry Modern societies (Dunbar & Spoors, 1995) Molecular genetics

Sexual signs and behavioral change Extracting energy from new sources Male investment Sexual signals Female signals elicit behavior change in males The material value of menstruation

Female coalitionary strategies: proto-ritual Coalitionary strategies Manipulating menstrual signals Recruits male investment for female coaltions Sham menstruation (Power & Watts, 1996) Evolved into ritualistic displays involving: Red paint Song Dance

Menstrual ritual as costly signal of commitment Cooperation vs. self-interest? Commitments Menstrual ritual: hard-to-fake Speech: easy-to-fake

Predictions from ‘sham menstruation’ model: archeological evidence Predicts increased male attraction to cosmetics Red pigment Evolution of ritual (Power & Watts, 1996) Increased stress on females Development of cosmetic rituals More abundant use of iron ochre Archeological evidence supports these predictions

Evidence of ethnography: female alliances, puberty rituals, and cosmetics Rituals associated with onset of menses 1. Advertise prospective fertility in coalitional contexts 2. Menstruant participants as probationers until initiated Traditional Cultures E.g., Venda of the Transvaal

Conclusion: ritual and the gossip hypothesis Model: ritual as costly signaling of commitment (hard-to-fake) Origins of ritual developed in collective manipulation of menstrual signals Necessary for establishing ‘gossip’ as a basis of trust Menstrual ritual = Super grooming Conclusion: a necessary condition for the evolution of language as gossip is the coevolution of ritual

Synchrony and ritual in the Andes Synchronized opioidergic activity Social bonding Analgesia Rituals as a signal of commitment Social bonding