Peaceful Intergroup Research Articles

Janus faced: The co-evolution of war and peace in the human species.

The human species presents a paradox. No other species possesses the propensity to carry out coalitionary lethal attacks on adult conspecifics coupled with the inclination to establish peaceful relations with genetically unrelated groups. What explains this seemingly contradictory feature? Existing perspectives, the "deep roots" and "shallow roots" of war theses, fail to capture the plasticity of human intergroup behaviors, spanning from peaceful cooperation to warfare. By contrast, this article argues that peace and war have both deep roots, and they co-evolved through an incremental process over several million years. On the one hand, humans inherited the propensity for coalitionary lethal violence from their chimpanzee-like ancestor. Specifically, having first inherited the skills to engage in cooperative hunting, they gradually repurposed such capacity to execute coalitionary killings of adult conspecifics and subsequently enhanced it through technological innovations like the use of weapons. On the other hand, they underwent a process of cumulative cultural evolution and, subsequently, of self-domestication which led to heightened cooperative communication and increased prosocial behavior within and between groups. The combination of these two biocultural evolutionary processes-coupled with feedback loop effects between self-domestication and Pleistocene environmental variability-considerably broadened the human intergroup behavioral repertoire, thereby producing the distinctive combination of conflictual and peaceful intergroup relations that characterizes our species. To substantiate this argument, the article synthesizes and integrates the findings from a variety of disciplines, leveraging evidence from evolutionary anthropology, primatology, archeology, paleo-genetics, and paleo-climatology.

Economic games for the study of peace.

Economic games provide models of real-world contexts in which researchers can probe dispositional and structural determinants of intergroup relations. Most intergroup games focus on determinants of aggression between groups and constrain the possibilities for peace. However, paradigms such as the intergroup parochial and universal cooperation game allow for peaceful intergroup relations and can be adapted for the study of peace.

Group-structured cultural selection can explain both war and peace.

Glowacki recognizes the importance of norms in enabling war and peace, but does not focus on the cultural evolutionary mechanisms by which these norms are maintained. We highlight how group-structured cultural selection shapes the scale and nature of peaceful intergroup interactions. The mechanistic perspective reveals that there are many more cases of peaceful intergroup relations than the current account implies.

Decolonial Politics: State, Statelessness, and Coexistence in Peace

ABSTRACT Due to the colonial continuities encoded in postcolonial nation-states, formal decolonisation reproduced new dominations rather than peaceful intergroup coexistence. Reflecting on the ‘how’ of decolonial politics, I argue that self-determination beyond the nation-state and spatiotemporally embedded decolonial imaginations are the undecomposable components of decolonial politics. I exemplify the failures of the nation-state through Southern (Iraqi) Kurdistan and illustrate Western (Rojava-Syrian) Kurdistan as a possible example of stateless decolonial coexistence, despite major geopolitical and socio-historical stalemates. The argument contributes to peace studies in International Relations by rethinking inter-group coexistence at the intersection of violent geopolitics and decolonial imaginations.

Young generations’ hopelessness perpetuates long-term conflicts

Transforming long-term conflicts into peaceful intergroup relations is one of the most difficult challenges for humanity. Such meaningful social changes are often driven by young people. But do young people living in contexts of long-term conflicts believe that change is even possible? In a series of six studies (Ntotal = 119,671) over two decades and across two unrelated intractable conflicts in Israel/Palestine and Cyprus, we found that younger (compared to older) generations from both respective rival groups have less hope for peace, and consequently less conciliatory attitudes. We also show that this gradual improvement of peace-promoting emotions and attitudes with increasing age can be experimentally accelerated in young people through a virtual reality-based aging simulation. These findings provide a new perspective on the fundamental question of why long-term conflicts are so difficult to resolve and highlight the importance of instilling hope in young generations to advance peace processes.

The evolution of peace.

While some species have affiliative and even cooperative interactions between individuals of different social groups, humans are alone in having durable, positive-sum, interdependent relationships across unrelated social groups. Our capacity to have harmonious relationships that cross group boundaries is an important aspect of our species' success, allowing for the exchange of ideas, materials, and ultimately enabling cumulative cultural evolution. Knowledge about the conditions required for peaceful intergroup relationships is critical for understanding the success of our species and building a more peaceful world. How do humans create harmonious relationships across group boundaries and when did this capacity emerge in the human lineage? Answering these questions involves considering the costs and benefits of intergroup cooperation and aggression, for oneself, one's group, and one's neighbor. Taking a game theoretical perspective provides new insights into the difficulties of removing the threat of war and reveals an ironic logic to peace - the factors that enable peace also facilitate the increased scale and destructiveness of conflict. In what follows, I explore the conditions required for peace, why they are so difficult to achieve, and when we expect peace to have emerged in the human lineage. I argue that intergroup cooperation was an important component of human relationships and a selective force in our species history beginning at least 300 thousand years. But the preconditions for peace only emerged in the past 100 thousand years and likely coexisted with intermittent intergroup violence which would have also been an important and selective force in our species' history.

Collective violence and construction of peace culture in the Basque Country: two experiences of memory, recognition and forgiveness

Post-conflict societies must confront the past and build a culture of peace. Two interventions are presented here in the context of the Basque Country after the cessation of violence. The first, an intervention with the participation of victims of terrorism, where participants (N = 280 Mage = 19.83 SD = 1.29) were assigned to intervention and control groups. Results showed that participation in the programme produced more favourable attitudes towards intergroup forgiveness, intergroup empathy, and the mediating effect of self-transcending emotions. Second, the Citizenship Processes programme of memory and recognition (N = 31 Mage = 19.48 SD = 3.91). Results showed an increase in forgiveness, intergroup empathy and a change in outgroup emotions from before to after the intervention. The impact of both programmes was medium-high and the relevance of combining narratives that avoid competitive victimisation and promote peaceful intergroup attitudes is discussed.
 Received: 14 September 2021Accepted: 22 November 2021

Societies within peace systems avoid war and build positive intergroup relationships

A comparative anthropological perspective reveals not only that some human societies do not engage in war, but also that peaceful social systems exist. Peace systems are defined as clusters of neighbouring societies that do not make war with each other. The mere existence of peace systems is important because it demonstrates that creating peaceful intergroup relationships is possible whether the social units are tribal societies, nations, or actors within a regional system. Peace systems have received scant scientific attention despite holding potentially useful knowledge and principles about how to successfully cooperate to keep the peace. Thus, the mechanisms through which peace systems maintain peaceful relationships are largely unknown. It is also unknown to what degree peace systems may differ from other types of social systems. This study shows that certain factors hypothesised to contribute to intergroup peace are more developed within peace systems than elsewhere. A sample consisting of peace systems scored significantly higher than a comparison group regarding overarching common identity; positive social interconnectedness; interdependence; non-warring values and norms; non-warring myths, rituals, and symbols; and peace leadership. Additionally, a machine learning analysis found non-warring norms, rituals, and values to have the greatest relative importance for a peace system outcome. These results have policy implications for how to promote and sustain peace, cohesion, and cooperation among neighbouring societies in various social contexts, including among nations. For example, the purposeful promotion of peace system features may facilitate the international cooperation necessary to address interwoven global challenges such as global pandemics, oceanic pollution, loss of biodiversity, nuclear proliferation, and climate change.

Good refugees, bad migrants? Intergroup helping orientations toward refugees, migrants, and economic migrants in Germany

AbstractThe present study examined the effect of group labels on helping behavioral intentions toward displaced people in Germany. Specifically, it examined the impact of different labels evoking either voluntary or forced migration (i.e., migrants, economic migrants, and refugees) on different helping orientations (e.g., dependency vs. autonomy‐oriented helping) and if these effects occur via perceived intergroup threat, warmth and competence stereotypes. Participants (N = 304) were randomly assigned to one of three conditions (refugee vs. migrant vs. economic migrant) and read fabricated case vignettes, featuring a displaced person who arrived in Germany recently. Results showed that, as predicted, the use of different group labels affected the helping orientations of host society members, as well as, the stereotypes they held. No significant label effects were found for intergroup threat. While the label refugee evoked dependency‐oriented helping intentions and triggered paternalistic stereotypes, the label economic migrants increased opposition to help, decreased help affirmation and evoked envious stereotypes. Practical implications to strengthen peaceful intergroup relations between host society members and newcomers are discussed.

Group Cooperation, Carrying-Capacity Stress, and Intergroup Conflict.

Peaceful intergroup relations deteriorate when individuals engage in parochial cooperation and parochial competition. To understand when and why intergroup relations change from peaceful to violent, we present a theoretical framework mapping out the different interdependence structures between groups. According to this framework, cooperation can lead to group expansion and ultimately to carrying-capacity stress. In such cases of endogenously created carrying-capacity stress, intergroup relations are more likely to become negatively interdependent, and parochial competition can emerge as a response. We discuss the cognitive, neural, and hormonal building blocks of parochial cooperation, and conclude that conflict between groups can be the inadvertent consequence of human preparedness - biological and cultural - to solve cooperation problems within groups.

Low familiarity and similar ‘group strength’ between opponents increase the intensity of intergroup interactions in mountain gorillas (Gorilla beringei beringei)

Intergroup interactions in social animals can vary from hostile to affiliative and may be influenced by factors such as competitive ability, resource values and existing intergroup relationships. Despite the potential for intergroup interactions to affect individual fitness and group stability, few studies have comprehensively tested how social, demographic and ecological factors may simultaneously influence intergroup interactions. Using 13 years of continuous data on intergroup interactions (n = 464), group composition, range use and diet, we investigated the factors that influenced the initiation and escalation of intergroup interactions in a fully habituated subpopulation of mountain gorillas in Volcanoes National Park, Rwanda. The majority of interactions were non-physically agonistic (57%), while peaceful exchanges and physical aggression were less common (18% and 25% of interactions respectively). Solitary males and young dominant silverbacks were the most likely to initiate an interaction, presumably because these males have the highest incentive to attract mates. Aggressive interactions between a group and a solitary male involved a high number of participating group members, reflecting the incentive to avoid injury and infanticide associated with solitary male encounters. Aggression between social groups escalated when groups were similarly sized, perhaps because these groups have similar competitive abilities. Peaceful intergroup interactions most commonly involved opponents that contained familiar and related individuals, suggesting that the short dispersal distance of gorillas may facilitate kin-selected intergroup tolerance. Variation and plasticity in gorilla behaviour during intergroup interactions are therefore dependent on the opponent’s familiarity and threat level. Intergroup interactions can vary from aggressive physical disputes to tolerant intermingling among extra-group individuals. Competition for access to limiting resources can often influence the occurrence of aggressive intergroup competition, but may not be sufficient to describe peaceful mingling between groups in social species. We found that although the main driver of intergroup interactions may be mating competition between males, interactions between familiar social groups were significantly more peaceful than interactions involving unfamiliar groups. These findings suggest that maintaining social and kin relationships with neighbouring groups may act as a strategy for reducing conflict in group-structured social species.

The evolutionary anthropology of war

Evolutionary anthropologists seek to understand the evolution of warfare across multiple timescales, from the roots of warfare in the intergroup aggression of our primate ancestors, to the causes of warfare among contemporary societies today. While warfare remains a contentious subject, considerable evidence supports the view that warfare is a strategy by which coalitions of males cooperate to acquire and defend resources necessary for reproduction. This strategy is not the result of a single “instinct” for war, but is instead an emergent property resulting from evolved psychological mechanisms (such as xenophobia and parochial altruism). These mechanisms are sensitive to ecological and social conditions, such that the prevalence and patterns of warfare vary according to subsistence strategies, military technology, cultural institutions, and political and economic relations. When economic conditions enable intergroup relations to change from zero-sum to positive-sum games, peaceful intergroup relations can emerge.

Fighting the Good Fight

The rhetoric of good and evil is prevalent in many areas of society and is often used to garner support for "redemptive violence" (i.e., using violence to rid and save the world from evil). While evil is discussed in psychological literature, beliefs about good and evil have not received adequate empirical attention as predictors of violent versus peaceful intergroup attitudes. In four survey studies, we developed and tested novel measures of belief in evil and endorsement of redemptive violence. Across four different samples, belief in evil predicted greater support for violence and lesser support for nonviolent responses. These effects were, in most cases, mediated by endorsement of redemptive violence. Structural equation modeling suggested that need for cognitive closure predicts belief in evil, and that the effect of belief in evil on support for violence is independent of right-wing authoritarianism, religious fundamentalism, and dangerous world beliefs.

Tolerance by Surprise: Evidence for a Generalized Reduction in Prejudice and Increased Egalitarianism through Novel Category Combination

Prejudices towards different groups are interrelated, but research has yet to find a way to promote tolerance towards multiple outgroups. We devise, develop and implement a new cognitive intervention for achieving generalized tolerance based on scientific studies of social categorization. In five laboratory experiments and one field study the intervention led to a reduction of prejudice towards multiple outgroups (elderly, disabled, asylum seekers, HIV patients, gay men), and fostered generalized tolerance and egalitarian beliefs. Importantly, these effects persisted outside the laboratory in a context marked by a history of violent ethnic conflict, increasing trust and reconciliatory tendencies towards multiple ethnic groups in the Former Yugoslav Republic of Macedonia. We discuss the implications of these findings for intervention strategies focused on reducing conflict and promoting peaceful intergroup relations.

Intergroup conflicts among chimpanzees in Taï National Park: lethal violence and the female perspective

Intercommunity aggression in chimpanzees and primitive warfare in humans possess striking similarities, such as the common occurrence of large male coalitions, systematic control of territory boundaries, and lethal attacks on isolated individuals from neighboring groups. However, an important apparent contrast is the absence of recurrent peaceful interactions between neighboring groups of chimpanzees. We observed a remarkable range of behavior in intergroup encounters among three habituated communities of chimpanzees in Taï National Park, Côte d'Ivoire. Lethal attacks are documented in these study groups for the first time, as well as year-long exchanges of parous adult females and peaceful intergroup visits of mothers with infants. Demographic factors, including group size and number of adult males, are shown to affect the nature of intergroup interactions in ways not considered previously. A reconsideration of the difference in intergroup interactions between eastern and western chimpanzees is proposed including a more important consideration of the female's perspective. The inclusion of the new complexities in intergroup interactions in chimpanzees allows new parallels to be drawn with the evolution of primitive warfare in humans.

Cooperation and Conflict

Abstract. A conventional wisdom in the literature contends that without a system of formal enforcement, heterogeneous groups are unable to peacefully interact for mutual benefit and are prone to eruptions of violent conflict. This article maintains that the amount of such conflict has been dramatically overstated and the occurrence of peaceful interaction dramatically understated. The common view reverses the empirical reality of the world. Historical evidence indicates that where formal institutions are absent, heterogeneous individuals signal credibility to one another by engaging in shared customs and practices, enabling peaceful intergroup exchange. This evidence challenges prevailing beliefs and suggests that peaceful cooperation characterizes most heterogeneous group interaction.

Dispersed Male Networks in Western Gorillas

Although kin-selection theory has been widely used to explain the tendency of individuals to bias beneficial behaviors towards relatives living within the same social group [1], less attention has focused on kin-biased interactions between groups. For animal societies in which females emigrate, as is the case for mountain gorillas (Gorilla beringei beringei), encounters between males in different groups often involve aggressive displays that can escalate to physical violence and fatal injuries [2, 3]. However, recent findings on the little-studied western gorilla (Gorilla gorilla) indicate that interactions between social groups occur more frequently than they do in mountain gorillas and are often [4, 5], although not always [5, 6], surprisingly nonaggressive. We investigated the pattern of genetic relationships between individuals of different groups and found evidence suggesting a previously unrecognized “dispersed male network” social structure in western gorillas in which the single males leading social groups were usually related to one or more nearby males. We propose that this provides a basis for extra-group, kin-biased behaviors and may explain the reported peaceful intergroup interactions. Furthermore, these results suggest that a patrilocal social structure, in which males remain in their natal region and potentially benefit from kin associations, is a feature unifying African apes and humans.

Variable resource defense by the Tana River crested mangabey

Behavioral observations over 16 months of two groups of Tana River crested mangabeys (Cercocebus galeritus galeritus) in East Africa provide evidence, contrary to previous reports, for site-specific aggression and territorial exclusion. In addition, movements and vocal responses to neighboring group's long-call vocalizations vary temporally, reflecting seasonal variation in food availability and distribution. Patterns of response to neighboring groups are consistent with the hypothesis that resources should be defended only when it is economic to do so. When fruit resources are rare intergroup interactions are infrequent and groups use separate areas. As fruit availability increases, the distribution of diet species influences the type of interaction; peaceful intergroup interactions generally occur when mangabeys eat uniformly distributed species and aggressive interactions occur when mangabeys eat species with patchy distributions. Differences between male vocal responses and group spatial responses may reflect conflicting objectives of territorial defense by males and females.