The evolution of (intergroup) peace hinges on how we define groups and peace.

Glowacki defines peace as harmonious relationships between groups maintained without the threat of violence, where groups can be anything from families to nation states. However, defining such contentious concepts like "peace" and "groups" is a difficult task, and we discuss the implications of Glowacki's definitions for understanding intergroup relationships and their evolutionary history.

Long-distance social relationships can both undercut and promote local natural resource management.

The management of large common-pool resources, like fisheries and forests, is more difficult when more people and more communities can access them-a particular problem given increased population sizes, higher mobility and globalized trade in the Anthropocene. Social relationships spanning communities, such as kin relationships, business or trade relationships and friendships, can make management even more challenging by facilitating and transmitting norms of overharvesting. However, these long-distance relationships can also bolster management by transmitting norms for sustainability, promoting interdependence and laying the groundwork for nested management systems.

Generalized morality culturally evolves as an adaptive heuristic in large social networks.

Why do people assume that a generous person should also be honest? Why do we even use words like "moral" and "immoral"? We explore these questions with a new model of how people perceive moral character. We propose that people vary in the extent to which they perceive moral character as "localized" (varying along many contextually embedded dimensions) versus "generalized" (varying along a single dimension from morally bad to morally good). This variation might be partly the product of cultural evolutionary adaptations to different kinds of social networks.

Lying about the future: Shuar-Achuar epistemic norms, predictions, and commitments.

Is there variation across cultures in what counts as a lie? Here we present evidence for a potentially unique conceptualization of lying in Shuar-Achuar communities in Ecuador, contrasting this conceptualization with people in twelve other countries and non-Shuar-Achuar Ecuadorians. In Shuar-Achuar communities, but not others, predictions of the future that turn out to be false are considered lies, even when the events that render them false are unforeseen. Failed commitments, on the other hand, are not seen as lies when unforeseen events prevent them from being kept.

Hearing Prosocial Stories Increases Hadza Hunter-Gatherers' Generosity in an Economic Game.

Folk stories featuring prosocial content are ubiquitous across cultures. One explanation for the ubiquity of such stories is that stories teach people about the local socioecology, including norms of prosociality, and stories featuring prosocial content may increase generosity in listeners. We tested this hypothesis in a sample of 185 Hadza hunter-gatherers.

Hadza hunter-gatherers with greater exposure to other cultures share more with generous campmates.

Humans are motivated to compete for access to valuable social partners, which is a function of their willingness to share and ability to generate resources. However, relative preferences for each trait should be responsive to socioecological conditions. Here, we test the flexibility of partner choice psychology among Hadza hunter-gatherers of Tanzania.

Evidence against the "anomalous-is-bad" stereotype in Hadza hunter gatherers.

People have an "anomalous-is-bad" stereotype whereby they make negative inferences about the moral character of people with craniofacial anomalies like scars. This stereotype is hypothesized to be a byproduct of adaptations for avoiding pathogens. However, evidence for the anomalous-is-bad stereotype comes from studies of European and North American populations; the byproduct hypothesis would predict universality of the stereotype.

Hunter-Gatherers Maintain Assortativity in Cooperation despite High Levels of Residential Change and Mixing.

Widespread cooperation is a defining feature of human societies from hunter-gatherer bands to nation states [1, 2], but explaining its evolution remains a challenge. Although positive assortment of cooperators is recognized as a basic requirement for the evolution of cooperation, the mechanisms governing assortment are debated. Moreover, the social structure of modern hunter-gatherers, characterized by high mobility, residential mixing, and low genetic relatedness [3], undermines assortment and adds to the puzzle of how cooperation evolved.

Hadza Men With Lower Voice Pitch Have a Better Hunting Reputation.

Previous research with hunter-gatherers has found that women perceive men with voices manipulated to be lower in pitch to be better hunters, and men perceive women with lower pitch to be better gatherers. Here, we test if actual voice pitch is associated with hunting and gathering reputations in men and women, respectively. We find that voice pitch does relate to foraging reputation in men, but not in women, with better hunters having a lower voice pitch.

Development of a Low-Cost Medical Ultrasound Scanner Using a Monostatic Synthetic Aperture.

Objective: In this paper, we present the design of low-cost medical ultrasound scanners aimed at the detection of maternal mortality risk factors in developing countries.

Method: Modern ultrasound scanners typically employ a high element count transducer array with multichannel transmit and receive electronics. To minimize hardware costs, we employ a single piezoelectric element, mechanically swept across the target scene, and a highly cost-engineered single channel acquisition circuit.

Winners, losers, and posers: The effect of power poses on testosterone and risk-taking following competition.

A contribution to a special issue on Hormones and Human Competition. The effect of postural power displays (i.e.