Historical myths define group boundaries: A mathematical sketch and evidence from Ukraine.

The authors' proposal for the evolutionary origins of historical myths does not hold up to scrutiny, as illustrated by a simple mathematical model. Group-level explanations, such as defining the conditions for in-group membership, are dismissed by the authors but are far more plausible, as illustrated by the ongoing war in Ukraine.

Constraints on cooperation shape hierarchical versus distributed structure in human groups.

Some human groups are organized hierarchically and some are distributed. Both types of groups occur in economic, political, and military domains, but it is unclear why hierarchical organizations are favored in certain contexts and distributed organizations are favored in others. I propose that these different organizational structures can be explained by human groups having different constraints on their ability to foster cooperation within the group.

Combat stress in a small-scale society suggests divergent evolutionary roots for posttraumatic stress disorder symptoms.

Military personnel in industrialized societies often develop posttraumatic stress disorder (PTSD) during combat. It is unclear whether combat-related PTSD is a universal evolutionary response to danger or a culture-specific syndrome of industrialized societies. We interviewed 218 Turkana pastoralist warriors in Kenya, who engage in lethal cattle raids, about their combat experiences and PTSD symptoms.

Integrating models of cognition and culture will require a bit more math.

We support the goal to integrate models of culture and cognition. However, we are not convinced that the free energy principle and Thinking Through Other Minds will be useful in achieving it. There are long traditions of modeling both cultural evolution and cognition.

An evolutionary theory of large-scale human warfare: Group-structured cultural selection.

When humans wage war, it is not unusual for battlefields to be strewn with dead warriors. These warriors typically were men in their reproductive prime who, had they not died in battle, might have gone on to father more children. Typically, they are also genetically unrelated to one another.

Many important group-level traits are institutions.

Smaldino makes a solid contribution to the literature on the evolution of human social organization by pointing out that group-level-traits (GLTs) often emerge from the interactions of group members in such a way that their effects are not easily partitioned into individual selection. However, we argue that he too readily dismisses institutional analysis as a tool for understanding these traits.