The history of research on peace and war (broadly used here to describe aggressive between-group interactions) is full of debates, mainly related to whether humans are inherently peaceful or violent and to whether evolutionary or cultural forces shape our behaviour (e.g., Fry, Reference Fry2013; Majolo, Reference Majolo2019). Researchers have often investigated the causes and consequences of war, but sometimes neglected to focus on peaceful interactions. However, there is a growing literature on the evolutionary, socioecological, and cultural factors shaping the maintenance and restoration of peaceful interactions between groups (e.g., Pisor & Surbeck, Reference Pisor and Surbeck2019). Glowacki provides a detailed critical evaluation of the challenges humans face when they attempt to maintain or restore peace. Below I critically evaluate four main points that emerge from Glowacki's study, in relation to the existing literature on the topic.
The first point is that the integration of genetic and cultural evolution into a unified theory (Henrich & McElreath, Reference Henrich and McElreath2003; Laland et al., Reference Laland, Uller, Feldman, Sterelny, Müller, Moczek and Odling-Smee2015) is leading to the progressive abandonment, at least in the biology-grounded disciplines, of the old-fashioned, erroneous dichotomy between genetic and cultural drivers of human behaviour. However, some clarifications are still necessary. It is time to stop using the gene versus culture approach and to start focusing on how genetic evolution can drive cultural diversification, and vice versa, an approach that has been successfully used in several studies (e.g., lactose digestion: Holden & Mace, Reference Holden and Mace2009). Moreover, using evolutionary explanations to describe a behaviour rarely means that that behaviour is innate, fixed, or always displayed; it means that there is an evolved propensity to display that behaviour under specific socioecological conditions. Clearly, something as complex as peace (or war) cannot be described by a set of fixed, innate responses that do not consider the socioecological challenges that an individual or group face. At the same time, humans have to regularly cope with collective action problems and prisoner's dilemma scenarios (Maynard Smith, Reference Maynard Smith1982): These can be addressed via group-specific rituals and norms, but the challenges they pose are universal and our responses to them are likely rooted in our evolutionary history. Analyses that integrate our evolved propensity to solve these challenges with the emergence and design of norms and rituals that can maintain peace are a more powerful way to explain human behaviour than putting genetic evolution and cultural forces in contrast to one another.
The second point is that peace cannot simply be described by the lack of war, but it requires the evolution and emergence of cultural practices that maintain tolerance and cooperation, reduce the risk of escalation of conflicts of interest, and restore peace when violence is unavoidable. Kim and Kissel (Reference Kim and Kissel2018) define these practices “peacefare.” Glowacki's study goes in this direction, when he effectively highlights how game theory can explain the challenges of restoring or maintaining peace. The recognition that peace requires the active solution of collective action problems and not “just” the avoidance of war is important, because it highlights that similar socioecological challenges can be solved either peacefully or aggressively. Humans faced both genetic and cultural evolutionary pressure to peacefully solve collective action problems.
The third point is that peace and war are intertwined phenomena. Peaceful and aggressive interactions between groups can sometimes be mutually exclusive to one another, in time or space. However, they may also occur simultaneously; for example, in modern warfare it is common for two countries to organise peace talks while they are still fighting each other. Moreover, prosocial behaviours that aim to maintain peace and cooperation can be extremely violent. Altruistic punishment may result in the killing of free-riders. Similarly, capital punishment of the most violent members of a group is often an effective way to restore peace and break the chain of reciprocal revenge that may “lock” two groups into a long-term period of conflict (target article). Various authors have suggested that peace and war coevolved (e.g., Bowles, Reference Bowles2009; target article). Indeed, humans have to cope with collective action problems both when they try to maintain peace and when they wage war. Shared intentionality, theory of mind, and our capacity for large-scale cooperation and for keeping track of resources exchanged with other individuals/groups, are some of the key cognitive and behavioural traits that can be effectively used to maintain a long period of peace between two groups or to wage a deadly war against our enemies. As Glowacki effectively points out, the intertwined nature of peace and war means that attempts to determine whether humans are inherently peaceful or violent are futile, because we, as a species, are a combination of both.
The fourth point is that an in-depth investigation of the origin, causes, and consequences of peace and war should be a collegial effort: It cannot be undertaken by a single discipline or without comparing different study populations or species. For example, the diversity, across human societies, of socioecological conditions, rituals, and norms leading to peace and war (Fry, Reference Fry2013; target article) requires an integration of anthropology, ethnography, and psychology with gene–culture evolution, in order to explain the sources of such diversity. Glowacki argues that the main evolutionary changes, that led to the way modern humans maintain peace, wage war, and tackle collective action problems, occurred relatively recently in our evolutionary past (i.e., in the last 300,000 years). Consequently, he mainly focuses on prestate and modern human societies. While this approach has merit, it should not discourage researchers from comparing how humans and other species tackle collective action problems related to cooperation or violence. Such comparative work should not simply focus on the two extant, most closely related species to humans (chimpanzees and bonobos), but it should include other primates, mammals, and birds to better identify the evolution of key cognitive and behavioural transitions affecting peace and war (e.g., Gómez, Verdú, & González-Megías, Reference Gómez, Verdú and González-Megías2021). The often claimed uniqueness of humans (e.g., in terms of capacity of large-scale cooperation or of waging deadly wars) rests on the assumption that we have a deep knowledge of the behaviour of other animal taxa.
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The history of research on peace and war (broadly used here to describe aggressive between-group interactions) is full of debates, mainly related to whether humans are inherently peaceful or violent and to whether evolutionary or cultural forces shape our behaviour (e.g., Fry, Reference Fry2013; Majolo, Reference Majolo2019). Researchers have often investigated the causes and consequences of war, but sometimes neglected to focus on peaceful interactions. However, there is a growing literature on the evolutionary, socioecological, and cultural factors shaping the maintenance and restoration of peaceful interactions between groups (e.g., Pisor & Surbeck, Reference Pisor and Surbeck2019). Glowacki provides a detailed critical evaluation of the challenges humans face when they attempt to maintain or restore peace. Below I critically evaluate four main points that emerge from Glowacki's study, in relation to the existing literature on the topic.
The first point is that the integration of genetic and cultural evolution into a unified theory (Henrich & McElreath, Reference Henrich and McElreath2003; Laland et al., Reference Laland, Uller, Feldman, Sterelny, Müller, Moczek and Odling-Smee2015) is leading to the progressive abandonment, at least in the biology-grounded disciplines, of the old-fashioned, erroneous dichotomy between genetic and cultural drivers of human behaviour. However, some clarifications are still necessary. It is time to stop using the gene versus culture approach and to start focusing on how genetic evolution can drive cultural diversification, and vice versa, an approach that has been successfully used in several studies (e.g., lactose digestion: Holden & Mace, Reference Holden and Mace2009). Moreover, using evolutionary explanations to describe a behaviour rarely means that that behaviour is innate, fixed, or always displayed; it means that there is an evolved propensity to display that behaviour under specific socioecological conditions. Clearly, something as complex as peace (or war) cannot be described by a set of fixed, innate responses that do not consider the socioecological challenges that an individual or group face. At the same time, humans have to regularly cope with collective action problems and prisoner's dilemma scenarios (Maynard Smith, Reference Maynard Smith1982): These can be addressed via group-specific rituals and norms, but the challenges they pose are universal and our responses to them are likely rooted in our evolutionary history. Analyses that integrate our evolved propensity to solve these challenges with the emergence and design of norms and rituals that can maintain peace are a more powerful way to explain human behaviour than putting genetic evolution and cultural forces in contrast to one another.
The second point is that peace cannot simply be described by the lack of war, but it requires the evolution and emergence of cultural practices that maintain tolerance and cooperation, reduce the risk of escalation of conflicts of interest, and restore peace when violence is unavoidable. Kim and Kissel (Reference Kim and Kissel2018) define these practices “peacefare.” Glowacki's study goes in this direction, when he effectively highlights how game theory can explain the challenges of restoring or maintaining peace. The recognition that peace requires the active solution of collective action problems and not “just” the avoidance of war is important, because it highlights that similar socioecological challenges can be solved either peacefully or aggressively. Humans faced both genetic and cultural evolutionary pressure to peacefully solve collective action problems.
The third point is that peace and war are intertwined phenomena. Peaceful and aggressive interactions between groups can sometimes be mutually exclusive to one another, in time or space. However, they may also occur simultaneously; for example, in modern warfare it is common for two countries to organise peace talks while they are still fighting each other. Moreover, prosocial behaviours that aim to maintain peace and cooperation can be extremely violent. Altruistic punishment may result in the killing of free-riders. Similarly, capital punishment of the most violent members of a group is often an effective way to restore peace and break the chain of reciprocal revenge that may “lock” two groups into a long-term period of conflict (target article). Various authors have suggested that peace and war coevolved (e.g., Bowles, Reference Bowles2009; target article). Indeed, humans have to cope with collective action problems both when they try to maintain peace and when they wage war. Shared intentionality, theory of mind, and our capacity for large-scale cooperation and for keeping track of resources exchanged with other individuals/groups, are some of the key cognitive and behavioural traits that can be effectively used to maintain a long period of peace between two groups or to wage a deadly war against our enemies. As Glowacki effectively points out, the intertwined nature of peace and war means that attempts to determine whether humans are inherently peaceful or violent are futile, because we, as a species, are a combination of both.
The fourth point is that an in-depth investigation of the origin, causes, and consequences of peace and war should be a collegial effort: It cannot be undertaken by a single discipline or without comparing different study populations or species. For example, the diversity, across human societies, of socioecological conditions, rituals, and norms leading to peace and war (Fry, Reference Fry2013; target article) requires an integration of anthropology, ethnography, and psychology with gene–culture evolution, in order to explain the sources of such diversity. Glowacki argues that the main evolutionary changes, that led to the way modern humans maintain peace, wage war, and tackle collective action problems, occurred relatively recently in our evolutionary past (i.e., in the last 300,000 years). Consequently, he mainly focuses on prestate and modern human societies. While this approach has merit, it should not discourage researchers from comparing how humans and other species tackle collective action problems related to cooperation or violence. Such comparative work should not simply focus on the two extant, most closely related species to humans (chimpanzees and bonobos), but it should include other primates, mammals, and birds to better identify the evolution of key cognitive and behavioural transitions affecting peace and war (e.g., Gómez, Verdú, & González-Megías, Reference Gómez, Verdú and González-Megías2021). The often claimed uniqueness of humans (e.g., in terms of capacity of large-scale cooperation or of waging deadly wars) rests on the assumption that we have a deep knowledge of the behaviour of other animal taxa.
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