Leadership and Status in Mammalian Societies: Context Matters

The interaction between cortisol and testosterone predicts leadership within rock hyrax social groups

Group movement leadership is associated with higher risks for those in the front. Leaders are the first to explore new areas and may be exposed to predation. Individual differences in risk-taking behavior may be related to hormonal differences. In challenging circumstances, such as risk-taking leadership that may pose a cost to the leader, cortisol is secreted both to increase the likelihood of survival by restoring homeostasis, and to mediate cooperative behavior. Testosterone too has a well-established role in risk-taking behavior, and the dual-hormone hypothesis posits that the interaction of testosterone and cortisol can predict social behavior. Based on the dual-hormone hypothesis, we investigated here whether the interaction between testosterone and cortisol can predict risk-taking leadership behavior in wild rock hyraxes (Procavia capensis). We used proximity loggers, observations, and playback trials to characterize hyrax leaders in three different leadership contexts that varied in their risk levels. In support of the dual-hormone hypothesis, we found that cortisol and testosterone interactions predict leadership that involves risk. Across different circumstances that involved low or high levels of risk, testosterone was positively related to leadership, but only in individuals (both males and females) with low levels of cortisol. We also found an interaction between these hormone levels and age at the low-risk scenarios. We suggest that the close social interactions and affiliative behavior among hyrax females within small egalitarian groups may make female leadership less risky, and therefore less stressful, and allow female leaders to influence group activities.

Mechanisms of equality and inequality in mammalian societies

The extent of (in)equality is highly diverse across species of social mammals, but we have a poor understanding of the factors that produce or inhibit equitable social organizations. Here, we adopt a comparative evolutionary perspective to test whether the evolution of social dominance hierarchies, a measure of social inequality in animals, exhibits phylogenetic conservatism and whether interspecific variation in these traits can be explained by sex, age or captivity. We find that hierarchy steepness and directional consistency evolve rapidly without any apparent constraint from evolutionary history. Given this extraordinary variability, we next consider multiple factors that have evolved to mitigate social inequality. Social networks, coalitionary support and knowledge transfer advantage to privilege some individuals over others. Nutritional access and prenatal stressors can impact the development of offspring, generating health disparities with intergenerational consequences. Intergenerational transfer of material resources (e.g. stone tools, food stashes, territories) advantage those who receive. Nonetheless, many of the same social species that experience unequal access to food (survival) and mates (reproduction) engage in levelling mechanisms such as food sharing, adoption, revolutionary coalitions, forgiveness and inequity aversion. Taken together, mammals rely upon a suite of mechanisms of (in)equality to balance the costs and benefits of group living. This article is part of the theme issue 'Evolutionary ecology of inequality'.

Sex bias in intergroup conflict and collective movements among social mammals: male warriors and female guides

Intergroup conflict is a major evolutionary force shaping animal and human societies. Males and females should, on average, experience different costs and benefits for participating in collective action. Specifically, among mammals, male fitness is generally limited by access to mates whereas females are limited by access to food and safety. Here we analyse sex biases among 72 species of group-living mammals in two contexts: intergroup conflict and collective movements. Our comparative phylogenetic analyses show that the modal mammalian pattern is male-biased participation in intergroup conflict and female-biased leadership in collective movements. However, the probability of male-biased participation in intergroup conflicts decreased and female-biased participation increased with female-biased leadership in movements. Thus, female-biased participation in intergroup conflict only emerged in species with female-biased leadership in collective movements, such as in spotted hyenas and some lemurs. Sex differences are probably attributable to costs and benefits of participating in collective movements (e.g. towards food, water, safety) and intergroup conflict (e.g. access to mates or resources, risk of injury). Our comparative review offers new insights into the factors shaping sex bias in leadership across social mammals and is consistent with the 'male warrior hypothesis' which posits evolved sex differences in human intergroup psychology. This article is part of the theme issue 'Intergroup conflict across taxa'.

Third-Party Perceptions of Male and Female Status: Male Physical Strength and Female Physical Attractiveness Cue High Status

Status is a universal feature of human sociality. A lesser-studied adaptive problem surrounding status is assessing who has which levels of status in a given group (e.g., identifying which people possess high status). Here, we integrate theory and methods from evolutionary social science, animal behavior, and social psychology, and we use an emotion inference paradigm to investigate what cues render people high status in the eyes of social perceivers. This paradigm relies on robust associations between status and emotion display—particularly the anger display. If a target is expected to enact (but not necessarily feel) anger, this would suggest that social perceivers view that target as higher status. By varying target attributes, we test whether those attributes are considered status cues in the eyes of social perceivers. In two well-powered, pre-registered experiments in the United States (N = 451) and India (N = 378), participants read one of eight vignettes about a male or female target—described as high or low in either physical strength or physical attractiveness (possible status cues)—who is thwarted by another person, and then reported expectations of the target’s felt and enacted anger. We find that people expected physically stronger (versus less strong) men and more (versus less) physically attractive women to enact greater anger when thwarted by a same-sex other. Strength had no significant effect on estimations of female status and attractiveness had no significant effect on estimations of male status. There were no differences in expectations of felt anger. Results suggest that people use men’s strength and women’s attractiveness as status cues. Moreover, results underscore the notion that focusing on male-typical cues of status might obscure our understanding of the female status landscape. We discuss how this paradigm might be fruitfully employed to examine and discover other unexplored cues of male and female status.

Sex-associated and context-dependent leadership in the rock hyrax

In many mammalian species, both sexes may take leadership role, but different traits may play a role in determining variation within species. Here we examine the effect of sex on leadership. We present three complementary datasets derived from a well-studied population of wild rock hyrax (Procavia capensis). The findings demonstrated that male and female rock hyraxes take on different leadership positions, depending on the context. When risk is moderate, more likely to lead are younger resident males, which experience high cortisol and lower testosterone levels. However, during acute predation scenarios, more likely to lead are males with lower centrality status. We suggest that hyrax males exhibit risky behaviors that may reflect their need for self-advertisement. In contrast, leadership among group females is more equally distributed. Females have little to gain from risky actions due to the lack of competition among them, but nonetheless take leadership positions.

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Different traits play a role in hyrax male and female leaders, in different contexts

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On moderate risk, younger resident males with high cortisol and low testosterone lead

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During predation scenario, lower centrality status males lead

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Among group females, leadership is more equally distributed

Social hierarchies and social networks in humans

Across species, social hierarchies are often governed by dominance relations. In humans, where there are multiple culturally valued axes of distinction, social hierarchies can take a variety of forms and need not rest on dominance relations. Consequently, humans navigate multiple domains of status, i.e. relative standing. Importantly, while these hierarchies may be constructed from dyadic interactions, they are often more fundamentally guided by subjective peer evaluations and group perceptions. Researchers have typically focused on the distinct elements that shape individuals' relative standing, with some emphasizing individual-level attributes and others outlining emergent macro-level structural outcomes. Here, we synthesize work across the social sciences to suggest that the dynamic interplay between individual-level and meso-level properties of the social networks in which individuals are embedded are crucial for understanding the diverse processes of status differentiation across groups. More specifically, we observe that humans not only navigate multiple social hierarchies at any given time but also simultaneously operate within multiple, overlapping social networks. There are important dynamic feedbacks between social hierarchies and the characteristics of social networks, as the types of social relationships, their structural properties, and the relative position of individuals within them both influence and are influenced by status differentiation. This article is part of the theme issue 'The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies'.

An Evolutionary Explanation for the Female Leadership Paradox

Social influence is distributed unequally between males and females in many mammalian societies. In human societies, gender inequality is particularly evident in access to leadership positions. Understanding why women historically and cross-culturally have tended to be under-represented as leaders within human groups and organizations represents a paradox because we lack evidence that women leaders consistently perform worse than men. We also know that women exercise overt influence in collective group-decisions within small-scale human societies, and that female leadership is pervasive in particular contexts across non-human mammalian societies. Here, we offer a transdisciplinary perspective on this female leadership paradox. Synthesis of social science and biological literatures suggests that females and males, on average, differ in why and how they compete for access to political leadership in mixed-gender groups. These differences are influenced by sexual selection and are moderated by socioecological variation across development and, particularly in human societies, by culturally transmitted norms and institutions. The interplay of these forces contributes to the emergence of female leaders within and across species. Furthermore, females may regularly exercise influence on group decisions in less conspicuous ways and different domains than males, and these underappreciated forms of leadership require more study. We offer a comprehensive framework for studying inequality between females and males in access to leadership positions, and we discuss the implications of this approach for understanding the female leadership paradox and for redressing gender inequality in leadership in humans.