In his target article, Glowacki provides a thorough and even-handed review of the ethnographic and archaeological records of intergroup conflict and peace, especially in small-scale nonstate societies, underscoring the flexibility of human sociality. Glowacki defines peace as an active (rather than passive) dyadic relationship between two groups, which can include everything from family units to nation states, built on top of intergroup tolerance (Pisor & Surbeck, Reference Pisor and Surbeck2019), trade and specialization (Fearon & Laitin, Reference Fearon and Laitin1996; target article, sect. 3.2, para. 2; sect. 3.2.1, para. 1), or the organization of motivated leaders (Olson, Reference Olson1965). By making his definitions of peace and groups explicit, Glowacki has helped us better explore the challenges scholars of human sociality face when discussing these topics.

Glowacki is clear that pacification (per Helbling, Reference Helbling, Otto, Thrane and Vandkilde2006) is not peace, a point of tension in the larger literature, stating that peace is “the expectation and presence of generally harmonious relationships not enforced with the threat of violence” (emphasis added; target article, sect. 1.1, para. 5). In essence, he makes the case that when internal, within-group threat of violence enforces harmonious relationships, that counts as peace, but when external threat of violence enforces harmonious relationships, it does not. This is in contrast to Glowacki's treatment of war, where he chooses not to distinguish internal and external warfare – even though he states that “the cultural tools that allow us to develop peaceful relationships are the very same ones that allow us to sometimes engage in total war” (target article, sect. 1, para. 5). His distinction between internal enforcement of peace and external enforcement of pacification is somewhat inconsistent with his treatment of state societies, where he notes that state societies can facilitate peace in nonstate small-scale societies by introducing physical punishment and execution – threats of violence – among other externally imposed institutions. This then raises the question of when nonstate small-scale societies pacified by states count as a different group from that state society, meaning they are subservient to the state and the relationship between the two is not peaceful, versus the same group as the state society, meaning they are merely in-group members encouraged to be peaceful through threat of violence. Similarly, if a subgroup within a society is dissatisfied and protests or rebels, how severe must the sanctions be before maintaining peace becomes pacification? In short, perhaps differentiating internal peace from external pacification is useful, but the issue of which relationships counts as peaceful and which do not should be further specified, especially as it interacts with how we distinguish between intra- and intergroup relations.

What constitutes a “group” also raises key questions about the timing of when peace emerges in our evolutionary history. Glowacki emphasizes the increased importance of intergroup peace in the late Pleistocene, a point on which we agree (Pisor & Ross, Reference Pisor and Ross2022), but de-emphasizes peace-building around the time of the origins of Homo (~2 million years ago). Glowacki defines social groups as ranging from families and kin groups to nation states. While the question of what constitutes a group in humans is contentious (see Moya, Reference Moya2022; Pietraszewski, Reference Pietraszewski2022, for relevant discussion), we largely agree with this inclusive definition. But if units as small as families or bands constitute groups, then peaceful intergroup relationships were likely fostered by exogamy long before the late Pleistocene – for example, around the origins of Homo (Chapais, Reference Chapais2008). However, Glowacki's focus on conflicts between societies, rather than between family units or bands, leads him to conclude that intergroup peace did not emerge until the late Pleistocene. For example, Glowacki argues that “prior to 700,000 years ago, there is little evidence that our hominin ancestors engaged in or would have needed to engage in intergroup cooperation” (target article, sect. 6, para. 2). However, intermarriage between kin groups was likely a powerful source of intergroup tolerance and alliances – and we view the latter as cooperation. In short, with such an inclusive definition of groups, human social organization in early Homo would have facilitated intergroup peace even if the products of this cooperation did not fossilize (e.g., Kramer, Reference Kramer2023; Pisor & Surbeck, Reference Pisor and Surbeck2019; Rodseth & Wrangham, Reference Rodseth, Wrangham, Chapais and Berman2004). Arguments of the timing of different events in the evolution of sociality necessarily hinge on definitions of peace and groups.

Glowacki's target article is a tour de force, synthesizing multiple fields of study and offering a more even-handed treatment of peace and flexibility in intergroup relationships than the existing literature. By making many assumptions explicit, he presents a fruitful avenue for future research on war and peace. Of course, making assumptions explicit makes them easier to critique and reflect upon. Here, we reflected upon two of his assumptions: The distinction between pacification and peace, and a seeming disconnect in the definition and treatment of groups. These have implications for the stories we tell about the evolutionary history of intergroup relationships. It behooves researchers of human sociality to revisit their assumptions about human sociality (e.g., Glowacki, Reference Glowacki2023b; Kramer, Reference Kramer2023; Moya, Reference Moya2022; Pietraszewski, Reference Pietraszewski2022; Pisor & Ross, Reference Pisor and Ross2022, Reference Pisor and Ross2023) as it can inform where the field is headed next. Glowacki's article accentuates areas of overlap between evolutionary anthropology and other social sciences and will further advance interdisciplinary research on the flexibility of human peace.