The evolution of intergroup tolerance in nonhuman primates and humans

Abstract

Primate individuals use a variety of strategies in intergroup encounters, from aggression to tolerance; however, recent focus on the evolution of either warfare or peace has come at the cost of characterizing this variability. We identify evolutionary advantages that may incentivize tolerance toward extra‐group individuals in humans and nonhuman primates, including enhanced benefits in the domains of transfer, mating, and food acquisition. We highlight the role these factors play in the flexibility of gorilla, chimpanzee, bonobo, and human behavior. Given humans have an especially broad range of intergroup behavior, we explore how the human foraging ecology, especially large spatial and temporal fluctuations in resource availability, may have selected for a greater reliance on tolerant between‐community relationships—relationships reinforced by status acquisition and cultural institutions. We conclude by urging careful, theoretically motivated study of behavioral flexibility in intergroup encounters in humans and the nonhuman great apes.

Stronger between-clan than within-clan contests and their ecological correlates in a non-territorial, fission-fusion species, the Asian elephant

“…Although opportunities for between-group competition are high in species with extensively overlapping home ranges, aggressive between-group encounters are thought to be rare in such species, perhaps due to large overlap being associated with low incentives from aggressive defense of territory/ranges (Cheney 1987, Pisor and Surbeck 2019, but see Wrangham 1980 for dominance-based avoidance as a reason for rare between-group aggression), in contrast to species wherein groups show more exclusive ranging that is associated with stronger territorial expression (for example, Willems and van Schaik 2015, see also Brown 2013). Interestingly, our findings of frequent between-clan agonistic encounters suggest that the Kabini grassland has an unusual competition regime.…”

“…The home ranges of clans may overlap extensively (for example, Baskaran and Desai 1996, Fernando et al . 2008), a trait that is usually related to infrequent aggression during between-clan encounters since less exclusive ranges are associated with lower incentives of between-group aggression (see Cheney 1987, Willems and van Schaik 2015, see also Brown 2013, Pisor and Surbeck 2019). Male Asian elephants disperse away from their natal groups (Desai and Johnsingh 1995, Vidya and Sukumar 2005) and are largely solitary thereafter (Keerthipriya et al .…”

Anti-Immigration Backlashes as Constraints

“…Human coalitions change frequently and inter-group exchanges in a context of multilevel, nested group structure are much older than once thought. In human evolutionary history, wars and epidemics were interspersed with frequent and beneficial exchanges of goods and partners (Pisor and Surbeck 2019).…”

Abnormal features of human self-domestication in bipolar disorder

“…Specifically, considering that BD impacts key aspects of our species-specific distinctive cognitive and behavioral phenotype, we have built on a particular hypothesis about the origins of our cognition and behavior, namely, the self-domestication account of human evolution. Briefly stated, humans are hypothesized to have experienced a domestication process similar to that underlying the evolution of domesticated strains of mammals, except that it was driven by intra-species factors such as co-parenting, changes in human foraging ecology, or the rise of community living (Hare et al, 2012; Pisor and Surbeck, 2019). This process of self-domestication is thought to have facilitated the emergence of many of our species-specific biological, cognitive, and behavioral features, including our sophisticated technology and culture (see Hare, 2017 for review).…”