Societies within peace systems avoid war and build positive intergroup relationships

The paper challenges the common assumption that all human societies engage in war and examines how some clusters of neighboring societies—termed peace systems—avoid warfare and cultivate cooperative intergroup relations. The authors propose that understanding the development and functioning of peace systems can inform efforts to promote positive inter-societal relationships in broader contexts, including regional and global levels. They hypothesize that peace systems are characterized by recurring features such as overarching identities, interconnectedness, interdependence, non-warring norms and values, peace-related myths/rituals/symbols, superordinate institutions, conflict management practices, and peace leadership. The study aims to test whether these features are more developed in peace systems than in comparable non-peace systems, and to assess the relative importance of these factors using machine learning.

Anthropological and historical research documents societies and regions that have sustained non-warring relationships, including the Iroquois Confederacy, Nordic nations, Swiss cantons, Australian Aboriginal groups in the Great Western Desert, mobile foragers of the Labrador Peninsula, and tribes of Brazil’s Upper Xingu River basin. Prior scholarship highlights mechanisms such as trade interdependence, shared rituals and ceremonies, anti-war values taught across generations, conflict resolution institutions, and the emergence of overarching social identities. Theoretical contributions suggest multiple reinforcing elements—shared identity, interconnectedness, positive histories, prosocial norms and values, symbols and rituals of peace, governance structures, and peace leadership—supporting durable intergroup peace. Archaeological work also indicates the existence of peace systems in prehistory. Despite these insights, the peace system concept has only recently been formalized, with limited systematic comparative analysis prior to this study.

Design: Comparative, cross-cultural analysis of 46 cases (peace systems and non-peace systems). Samples: The experimental sample comprised well-documented peace systems identified from anthropological and historical literature. The comparison sample consisted of 30 non-peace cases randomly selected from the Standard Cross-Cultural Sample (SCCS), with principal authority ethnographies used for coding. Total N=46 (implying 16 peace systems and 30 non-peace systems). Variables: Eight hypothesized peace-related features (overarching identity; interconnectedness; interdependence; non-warring values and norms; non-warring myths, rituals, and symbols; superordinate institutions; conflict management; peace leadership) plus war-related features (ethnocentrism; warring values and norms; war myths, rituals, and symbols; war leadership). Subcomponents were coded for interconnectedness (marriage, economic, political, positive historical ties) and interdependence (security, ecological, economic), and for values vs. norms and for peace myths vs. rituals vs. symbols. Data collection and coding: Sources were compiled per case; variables were coded using a standardized coding sheet. For comparison cases (SCCS), principal authority sources were used. Statistical analysis: Ordinal correlations (Kendall’s Tau) and two-sample Mann–Whitney U-tests (two-tailed) were conducted in SPSS v26; normality was not assumed. Missing values were mean-imputed. A Random Forest classifier (scikit-learn, n_estimators=100) assessed relative feature importance among variables that showed significant between-group differences by Mann–Whitney U (plus overarching governance to represent that hypothesis). Feature importances were extracted via feature_importances_.

- Correlations: Peace-related variables were positively intercorrelated; war-related variables were positively intercorrelated (with partial exception of ethnocentrism); peace-related variables were negatively correlated with war-related variables, with strong negative associations between peace vs. war values/norms and peace vs. war myths/rituals/symbols. - Group comparisons (peace systems vs. non-peace systems): - Peace-related variables: Peace systems scored significantly higher on overarching identity (p ≈ 0.003), interconnectedness (p ≈ 0.004), non-warring values and norms (p ≈ 0.003), and non-warring myths/rituals/symbols (p ≈ 0.003). Superordinate institutions (p ≈ 0.064, ns) and overall conflict management (p ≈ 0.193, ns) were not significantly different. Peace leadership was not significantly different in Table 2 (reported p ≈ 0.511). - War-related variables: Non-peace systems scored significantly higher on warring values and norms (p ≈ 0.002) and war myths/rituals/symbols (p ≈ 0.013); ethnocentrism was not significantly different. - Granular subcomponents (Table 3): - Interconnectedness: Economic (p ≈ 0.002) and positive historical interconnectedness (p < 0.001) were significantly greater in peace systems; intermarriage trended (p ≈ 0.060, ns); political interconnectedness was not significant. - Interdependence: Security (p ≈ 0.050), ecological (p ≈ 0.028), and economic (p ≈ 0.002) interdependence were all greater in peace systems. - Values/norms: Both non-warring values (p ≈ 0.001) and non-warring norms (p < 0.001) were greater in peace systems. - Peace culture elements: Peace rituals (p < 0.001) and peace symbols (p ≈ 0.006) were greater; peace myths were not significant (p ≈ 0.077). - Random Forest: The analysis indicated non-warring norms as the most important contributor to a peace outcome, followed by overarching identity and positive interconnectedness (narrative summary). A feature-importance table (provided) included high importance scores for non-warring norms and components of interdependence, among others.

The findings support the thesis that peace systems differ systematically from non-peace systems across multiple dimensions that reinforce cooperative, non-warring intergroup relations. Positive correlations among peace-related factors suggest mutually reinforcing dynamics: shared identities, interconnectedness, interdependence, prosocial norms/values, and peace-related cultural practices coalesce to stabilize non-warring relationships. Conversely, war-oriented features cluster together and inversely relate to peace features. Significant differences in economic and historical interconnectedness, and in all three types of interdependence, highlight material and relational linkages that may underpin peace systems. The prominence of non-warring norms and values—evidenced both by group differences and machine learning importance—indicates that cultural-normative orientations are central to sustaining peace, potentially making war among member societies inconceivable over time. Case narratives (e.g., Iroquois, Swiss, Nordic, EU) illustrate how overarching institutions and identities can evolve, with external threats (security interdependence) sometimes catalyzing integration. These patterns have implications for designing interventions to promote inter-societal cooperation in contemporary regional and global contexts.

The study advances a comparative framework for understanding peace systems and demonstrates that such systems share recurring features that distinguish them from non-peace contexts. Non-warring norms and values, overarching identities, interconnectedness, and interdependence are key elements, with peace rituals and symbols reinforcing prosocial orientations. Random Forest analysis further underscores the centrality of non-warring norms. Practically, fostering changeable peace-supporting factors—such as economic and historical interconnectedness, creation of superordinate institutions, and cultivation of shared identities and prosocial norms—may help transform conflict-prone systems into stable peace systems. Future research should: (1) examine longitudinal transformations from war to peace to identify causal drivers and sequences; (2) test generalizability across additional cases and social complexity levels; (3) refine measurement of leadership, institutions, and conflict management; and (4) explore how common global threats (e.g., climate change, pandemics) might catalyze broader peace system dynamics.

- Sample size constraints (N=46; 16 peace systems, 30 non-peace systems) limit statistical power and may yield Type II errors, particularly for variables like intermarriage and overall conflict management. - Case identification of peace systems is limited by the paucity of prior cataloging; known cases may not represent the full universe. - Coding relies on secondary sources and may introduce measurement error or bias; heterogeneity in social complexity across cases may obscure effects (e.g., superordinate institutions). - Cross-sectional, observational design limits causal inference and temporal ordering of features; historical transformation pathways remain under-specified. - Missing data imputed with means may attenuate variability and affect estimates.