Human Nature,

Review of Nam C. Kim and Marc Kissel’s Emergent Warfare in Our Evolutionary Past

Exploring Warfare and Violence from a Cross-Cultural Perspective Abstract This special issue of Human Nature presents selected works from the 2015 and 2017 “Warfare, Environment, Social Inequality, and Pro-Sociability” (WESIPS) conferences held at the Center for Cross-Cultural Study in Seville, Spain. These investigations explore the manifestations of indigenous warfare and violence from a host of theoretical perspectives. Topics range from the origins of warfare to the psychological repercussions of combat, the relationship between warfare and status, as well as the documentation of peace processes among warring groups. This issue also examines the effects of militarization and coercive conservation on indigenous peoples.

Prosocial Emotion, Adolescence, and Warfare Abstract Examining the costs and motivations of warfare is key to conundrums concerning the relevance of this troubling phenomenon to the evolution of social attachment and cooperation, particularly during adolescence and young adulthood—the developmental time period during which many participants are first recruited for warfare. The study focuses on Samburu, a pastoralist society of approximately 200,000 people occupying northern Kenya’s semi-arid and arid lands, asking what role the emotionally sensitized, peer-driven adolescent life stage may have played in the cultural and genetic coevolution of coalitional lethal aggression. Research in small-scale societies provides unparalleled opportunities for sharply defined variables, particularly in age generation societies in which all young men are initiated into “warriorhood.” Proposing an epigenetic and component behavior approach, we examine whether raiding activities such as number of raids, killing, and sparing enemy lives associate with DNA methylation in two candidate genes: MAOA, linked to mood and arousal, and NR3C1, linked to stress and immune response. We report statistically significant associations between the epigenetic variables and the combat (exposure) variables of overall raiding activity and reportedly showing mercy to enemies. In contrast, epigenetic variables did not associate with post-traumatic stress disorder (PTSD) symptom scores (a potential outcome measure), and the only combat variable associated with PTSD (but not DNA methylation) was losing one’s own livestock in a raid. These findings raise important questions concerning the mechanisms driving warfare’s paradoxical mix of violent and altruistic behaviors.

Is War in Our Nature? Abstract The Seville Statement on Violence rejected the view that violence and war were in any way rooted in human nature and proclaimed that they were merely a cultural artifact. This paper points out both the valid and invalid parts of the statement. It concludes that the potential for both war and peace is embedded in us. The human behavioral toolkit comprises a number of major tools, respectively geared for violent conflict, peaceful competition, or cooperation, depending on people’s assessment of what will serve them best in any given circumstance. Conflict is only one tool—the hammer—in our diverse behavioral toolkit. However, all three behavioral strategies are not purely learned cultural forms. This naive nature/nurture dichotomy overlooks the heavy and complex biological machinery that is necessary for the working of each of them and the interplay between them. They are all very close under our skin and readily activated because they have all been very handy during our long evolutionary past. At the same time, they are variably calibrated to particular conditions through social learning, which means that their relative use may fluctuate widely. Thus, state authority has tilted the menu of human choices in the direction of the peaceful options in the domestic arena, and changing economic, social, and political conditions may be generating a similar effect in the international arena.

Pacifying Hunter-Gatherers Abstract There is a well-entrenched schism on the frequency (how often), intensity (deaths per 100,000/year), and evolutionary significance of warfare among hunter-gatherers compared with large-scale societies. To simplify, Rousseauians argue that warfare among prehistoric and contemporary hunter-gatherers was nearly absent and, if present, was a late cultural invention. In contrast, so-called Hobbesians argue that violence was relatively common but variable among hunter-gatherers. To defend their views, Rousseauians resort to a variety of tactics to diminish the apparent frequency and intensity of hunter-gatherer warfare. These tactics include redefining war, censoring ethnographic accounts of warfare in comparative analyses, misconstruing archaeological evidence, and claiming that outside contact inflates the intensity of warfare among hunter-gatherers. These tactics are subject to critical analysis and are mostly found to be wanting. Furthermore, Hobbesians with empirical data have already established that the frequency and intensity of hunter-gatherer warfare is greater compared with large-scale societies even though horticultural societies engage in warfare more intensively than hunter-gatherers. In the end I argue that although war is a primitive trait we may share with chimpanzees and/or our last common ancestor, the ability of hunter-gatherer bands to live peaceably with their neighbors, even though war may occur, is a derived trait that fundamentally distinguishes us socially and politically from chimpanzee societies. It is a point often lost in these debates.

Social Signaling and the Warrior-Big-Man among the Western Dani Abstract We employ the Social Signaling Model (SSM) and life history of a Western Dani big-man, Tibenuk, to analyze a neglected curiosity in the career of the big-man type. The big-man is renowned as an economic entrepreneur, the master of material displays. In New Guinea, however, big-men had invariably first gained fame and some influence as eminent warriors. The SSM accounts for this two-part career path by proposing that small-scale social organization rests on honest, competitive signaling of individual and collective fighting strength, with leaders being those who excel in these contests. The performances for which big-men are already known, conspicuous ceremonial displays, broadcast this strength indirectly. Explicitly conceptualized as symbolic fighting, they constituted indexical proxies for their sponsors’ individual and collective willingness and ability to fight. Success on the battlefield, though, signaled fighting strength more directly. Men therefore had to demonstrate strength on both the battlefield and the ceremonial ground if they were to become big-men. This was Tibenuk’s achievement. When he was young and at his physical peak, he demonstrated outstanding capability in war. War is a young man’s game, however, and as his physical capacities waned, he shifted to politics, an older man’s game, honing his political talents and developing extensive political networks that allowed him to sponsor massive pig feasts, the principal form of conspicuous ceremonial display. Tibenuk’s career also reveals synergies between warrior and political talents that hitherto have been overlooked in big-man analysis.

The Impacts of Conservation and Militarization on Indigenous Peoples Abstract There has been a long-standing debate about the roles of San in the militaries of southern Africa and the prevalence of violence among the Ju/'hoansi and other San people. The evolutionary anthropology and social anthropological debates over the contexts in which violence and warfare occurs among hunters and gatherers are considered, as is the “tribal zone theory” of warfare between states and indigenous people. This paper assesses the issues that arise from these discussions, drawing on data from San in Angola, Namibia, Botswana, and Zimbabwe. Utilizing cases of how San have been affected by military forces and wildlife conservation agencies in what became protected areas in southern Africa, this article shows that indigenous peoples have been treated differentially by state and nongovernmental organizations involved in anti-poaching, shoot-to-kill, and forced resettlement policies. Particular emphasis is placed on the !Xun and Khwe San of southern Angola and northern Namibia and the Tshwa San of western Zimbabwe and northern Botswana, who have been impacted by militarization and coercive conservation efforts since the late nineteenth century. Principal conclusions are that conservation and militarization efforts have led to a reduction in land and resources available to indigenous people, higher levels of poverty, increased socioeconomic stratification, and lower levels of physical well-being. San have responded to these trends by engaging in social activism, forming community-based institutions, and pursuing legal actions aimed at obtaining human rights and equitable treatment.

Review of K. L. Kramer and B. F. Codding’s Why Forage? Hunters and Gatherers in the Twenty-First Century

When Saying “Sorry” Isn’t Enough: Is Some Suicidal Behavior a Costly Signal of Apology? Abstract Lethal and nonlethal suicidal behaviors are major global public health problems. Much suicidal behavior (SB) occurs after the suicide victim committed a murder or other serious transgression. The present study tested a novel evolutionary model termed the Costly Apology Model (CAM) against the ethnographic record. The bargaining model (BRM) sees nonlethal suicidal behavior as an evolved costly signal of need in the wake of adversity. Relying on this same theoretical framework, the CAM posits that nonlethal suicidal behavior can sometimes serve as an honest signal of apology in the wake of committing a severe transgression, thereby repairing valuable social relationships. To test this hypothesis, the CAM was operationalized into a set of variables, and two independent coders coded 473 text records on suicidal behavior from 53 cultures from the probability sample of the Human Relations Area Files. The results indicated that in ethnographic accounts of suicidal behavior, transgressions, punishment, and shame were relatively common, supporting the CAM, but explicit motives to apologize and evidence of forgiveness were rare, contrary to the CAM. The theoretical variables of the CAM nevertheless formed a cluster distinct from the BRM, and a subset of cases of suicidal behavior were largely related to transgressions and other CAM variables rather than BRM or other variables. Support for the CAM varied widely across cultures, but there was evidence for it in every major geographical region. Exploratory analyses suggested that the CAM is potentially more likely to occur in response to severe conflicts concerning transgressions committed against nonkin. Furthermore, in text records that involved transgressions, male suicidal behavior was most frequently associated with murder, whereas female suicidal behavior was most frequently associated with sexual transgressions. In conclusion, the results provided mixed support for the hypothesis that some instances of suicidal behavior function to send a costly signal of apology to those harmed by a transgression.

Evolutionary Models of Leadership Abstract This study tested four theoretical models of leadership with data from the ethnographic record. The first was a game-theoretical model of leadership in collective actions, in which followers prefer and reward a leader who monitors and sanctions free-riders as group size increases. The second was the dominance model, in which dominant leaders threaten followers with physical or social harm. The third, the prestige model, suggests leaders with valued skills and expertise are chosen by followers who strive to emulate them. The fourth proposes that in small-scale, kin-based societies, men with high neural capital are best able to achieve and maintain positions of social influence (e.g., as headmen) and thereby often become polygynous and have more offspring than other men, which positively selects for greater neural capital. Using multiple search strategies we identified more than 1000 texts relevant to leadership in the Probability Sample of 60 cultures from the Human Relations Area Files (HRAF). We operationalized the model with variables and then coded all retrieved text records on the presence or absence of evidence for each of these 24 variables. We found mixed support for the collective action model, broad support for components of the prestige leadership style and the importance of neural capital and polygyny among leaders, but more limited support for the dominance leadership style. We found little evidence, however, of emulation of, or prestige-biased learning toward, leaders. We found that improving collective actions, having expertise, providing counsel, and being respected, having high neural capital, and being polygynous are common properties of leaders, which warrants a synthesis of the collective action, prestige, and neural capital and reproductive skew models. We sketch one such synthesis involving high-quality decision-making and other computational services.