Competing for the benefit of offspring eliminates the gender gap in competitiveness

Gender disparities in material and educational resources differ by kinship system

Contemporary inequality exists at an unprecedented scale. Social scientists have emphasized the role played by material wealth in driving its escalation. Evolutionary anthropologists understand the drive to accumulate material wealth as one that is coupled ultimately to increasing reproductive success. Owing to biological caps on reproduction for women, the efficiency of this conversion can differ by gender, with implications for understanding the evolution of gender disparities in resource accumulation. Efficiency also differs according to the type of resources used to support reproductive success. In this paper, we review evolutionary explanations of gender disparities in resources and investigate empirical evidence to support or refute those explanations among matrilineal and patrilineal subpopulations of ethnic Chinese Mosuo, who share an ethnolinguistic identity, but differ strikingly in terms of institutions and norms surrounding kinship and gender. We find that gender differentially predicts income and educational attainment. Men were more likely to report income than women; amounts earned were higher for men overall, but the difference between men and women was minimal under matriliny. Men reported higher levels of educational attainment than women, unexpectedly more so in matrilineal contexts. The results reveal nuances in how biology and cultural institutions affect gender disparities in wealth. This article is part of the theme issue 'Evolutionary ecology of inequality'.

Married women with children experience greater intrasexual competition than their male counterparts

Human males are considered to be more competitive than females. However, females must also compete for resources necessary for their own and their offsprings' survival. Since females use more indirect forms of competition than males, comparing observable forms of competition may be misleading. One critical driver of competition is resource asymmetry. Since competition occurs primarily within sex, reactions to resource asymmetry with same-sex peers should provide an important measure of competitiveness. We asked 596 married participants, 25-45 years of age with at least one child from three different countries to evaluate how same-sex individuals they know would react to a target individual who had a valuable resource that the same-sex individuals did not have. Half the participants evaluated reactions to same-sex targets, while the other half evaluated reactions to other-sex targets. Participants reported that women would react more negatively than men to resource asymmetry with same-sex targets, but not other-sex targets. These results suggest that women may be even more competitive than men in contexts when important resources related to reproductive success are at stake.

Sustaining the potential for cooperation as female competitive strategy

The lower female competitiveness often found in economic experiments presents a puzzle. If accumulating wealth and reaching high status affords women essential benefits for themselves and their children, why do women appear less competitive? By looking at behavioural strategies from a cooperative breeding perspective, we propose that women may have evolved an adaptation to strategically suppress competitiveness to elicit cooperation for the benefit of raising offspring. To support this idea, we review the literature that shows that women's behaviour is, in general, more reactive than men's to the social conditions of the different games. In particular, we focus on our experimental work where we show that women are not less competitive than men once the games evoke a parenting frame (by substituting cash with rewards that could benefit the participants' offspring), a gender-typical one (by using vouchers for prizes acceptable as domain of female interests), or include a prosocial option (by allowing winners to share some of the gains with losers). We conclude that, for women, nurturing the potential for cooperation intertwines with competitiveness to produce a complex, adaptive female social strategy. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.

On the robustness of gender differences in economic behavior

Because of the importance of economic decisions, researchers have looked into what factors influence them. Gender has received a lot of attention for explaining differences in behavior. But how much can be associated with gender, and how much with an individual's biological sex? We run an experimental online study with cis- and transgender participants that (1) looks into correlational differences between gender and sex for competitiveness, risk-taking, and altruism by comparing decisions across these different subject groups. (2) we prime participants with either a masculine or feminine gender identity to examine causal gender effects on behavior. We hypothesize that if gender is indeed a primary factor for decision-making, (i) individuals of the same gender (but different sex) make similar decisions, and (ii) gender priming changes behavior. Based on 780 observations, we conclude that the role of gender (and sex) is not as decisive for economic behavior as originally thought.

Our Grandmothers' Legacy: Challenges Faced by Female Ancestors Leave Traces in Modern Women's Same-Sex Relationships

Investigations of women's same-sex relationships present a paradoxical pattern, with women generally disliking competition, yet also exhibiting signs of intrasexual rivalry. The current article leverages the historical challenges faced by female ancestors to understand modern women's same-sex relationships. Across history, women were largely denied independent access to resources, often depending on male partners' provisioning to support themselves and their children. Same-sex peers thus became women's primary romantic rivals in competing to attract and retain relationships with the limited partners able and willing to invest. Modern women show signs of this competition, disliking and aggressing against those who threaten their romantic prospects, targeting especially physically attractive and sexually uninhibited peers. However, women also rely on one another for aid, information, and support. As most social groups were patrilocal across history, upon marriage, women left their families to reside with their husbands. Female ancestors likely used reciprocal altruism or mutualism to facilitate cooperative relationships with nearby unrelated women. To sustain these mutually beneficial cooperative exchange relationships, women may avoid competitive and status-striving peers, instead preferring kind, humble, and loyal allies. Ancestral women who managed to simultaneously compete for romantic partners while forming cooperative female friendships would have been especially successful. Women may therefore have developed strategies to achieve both competitive and cooperative goals, such as guising their intrasexual competition as prosociality or vulnerability. These historical challenges make sense of the seemingly paradoxical pattern of female aversion to competition, relational aggression, and valuation of loyal friends, offering insight into possible opportunities for intervention.

Staying alive includes adaptations for catalyzing cooperation

The target article interprets women's lower competitiveness than men's as evidence of adaptation to help women avoid physical conflicts and stay alive. This commentary advances the additional hypothesis that strategically suppressing competitiveness, thus signaling egalitarian intentions, could be an adaptation to catalyze cooperative behavior from males and females, turning natural competitors (other women) into allies and men into supportive partners.

Hormonal contraceptives as disruptors of competitive behavior: Theoretical framing and review

Emerging evidence suggests that hormonal contraceptives (HCs) impact psychological outcomes through alterations in neurophysiology. In this review, we first introduce a theoretical framework for HCs as disruptors of steroid hormone modulation of socially competitive attitudes and behaviors. Then, we comprehensively examine prior research comparing HC users and non-users in outcomes related to competition for reproductive, social, and financial resources. Synthesis of 46 studies (n = 16,290) led to several key conclusions: HC users do not show the same menstrual cycle-related fluctuations in self-perceived attractiveness and some intrasexual competition seen in naturally-cycling women and, further, may show relatively reduced status- or achievement-oriented competitive motivation. However, there a lack of consistent or compelling evidence that HC users and non-users differ in competitive behavior or attitudes for mates or financial resources. These conclusions are tentative given the notable methodological limitations of the studies reviewed. Implications and recommendations for future research are discussed.

Competitiveness among Nandi female husbands

Differences in competitiveness between men and women have been hypothesized as a potential explanation for important differences in education and labor market outcomes. Central to the literature is whether these differences are innate or learned. I take advantage of the distinct cultural institution of “female husbands” (biologically females but socially men) in the Nandi society in Kenya to study this question. By keeping biological sex constant, holding the society constant, but altering the social gender at an adult age, this unique setting advances our understanding of these differences. Specifically, the results support the hypothesis that competitive inclinations are channeled through social roles and the family. Social norms and social identity critically matter to tackle differences between men and women directly.

In the Nandi society in Kenya, custom establishes that a woman’s “house property” can only be transmitted to male heirs. As not every woman gives birth to a male heir, the Nandi solution to sustain the family lineage is for the heirless woman to become the “female husband” to a younger woman by undergoing an “inversion” ceremony to “change” into a man. This biological female, now socially a man, becomes a “husband” and a “father” to the younger woman’s children, whose sons become the heirs of her property. Using this unique separation of biological sex and social roles holding constant the same society, I conduct competitiveness experiments. Similar to Western cultures, I find that Nandi men choose to compete at roughly twice the rate as Nandi women. Importantly, however, female husbands compete at the same rate as males, and thus around twice as often as females. These findings are robust to controlling for several risk aversion, selection, and behavioral factors. The results provide support for the argument that social norms, family roles, and endogenous preference formation are crucially linked to differences in competitiveness between men and women.

Climate Action for (My) Children

How do we motivate cooperation across the generations-between parents and children? Here we study voluntary climate action (VCA), which is costly to today's decision-makers but essential to enable sustainable living for future generations. We predict that "offspring observability" is critical: parents will be more likely to invest in VCA when their own offspring observes their action, whereas when adults or genetically unrelated children observe them, the effect will be smaller. In a large-scale lab-in-the-field experiment, we observe a remarkable magnitude of VCA: parents invest 82% of their 69€ endowment into VCA, resulting in almost 14,000 real trees being planted. Parents' VCA varies across conditions, with the largest treatment effect occurring when a parent's own child is the observer. In subgroup analyses, we find that larger treatment effects occur among parents with a high school diploma. Moreover, VCA for parents who believe in climate change is most affected by the presence of their own child. In contrast, VCA of climate change skeptical parents is most influenced by the presence of children to whom they are not related. Our findings have implications for policy-makers interested in designing programs to encourage voluntary climate action and sustaining intergenerational public goods.

Prosocial option increases women's entry into competition

We provide evidence that women enter competitions at the same rate as men when the incentive for winning includes the option to share part of the rewards with the losers (i.e., when the incentive system is socially oriented). Using an experiment (with N = 238 subjects from three laboratories), we find that about 16% more men than women choose to compete in the standard tournament; this gender gap is eliminated in the socially oriented incentive treatment. While men's choice to compete remains unchanged, at around 52% in both conditions, women increase their entry rate from 35% in the standard tournament to 60% when the incentive includes a socially oriented option.

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.

Pandemic Leadership: Sex Differences and Their Evolutionary-Developmental Origins

The COVID-19 pandemic has caused a global societal, economic, and social upheaval unseen in living memory. There have been substantial cross-national differences in the kinds of policies implemented by political decision-makers to prevent the spread of the virus, to test the population, and to manage infected patients. Among other factors, these policies vary with politicians' sex: early findings indicate that, on average, female leaders seem more focused on minimizing direct human suffering caused by the SARS-CoV-2 virus, while male leaders implement riskier short-term decisions, possibly aiming to minimize economic disruptions. These sex differences are consistent with broader findings in psychology, reflecting women's stronger empathy, higher pathogen disgust, health concern, care-taking orientation, and dislike for the suffering of other people-as well as men's higher risk-taking, Machiavellianism, psychopathy, narcissism, and focus on financial indicators of success and status. This review article contextualizes sex differences in pandemic leadership in an evolutionary framework. Evolution by natural selection is the only known process in nature that organizes organisms into higher degrees of functional order, or counteracts the unavoidable disorder that would otherwise ensue, and is therefore essential for explaining the origins of human sex differences. Differential sexual selection and parental investment between males and females, together with the sexual differentiation of the mammalian brain, drive sex differences in cognition and behavioral dispositions, underlying men's and women's leadership styles and decision-making during a global pandemic. According to the sexually dimorphic leadership specialization hypothesis, general psychobehavioral sex differences have been exapted during human evolution to create sexually dimorphic leadership styles. They may be facultatively co-opted by societies and/or followers when facing different kinds of ecological and/or sociopolitical threats, such as disease outbreaks or intergroup aggression. Early evidence indicates that against the invisible viral foe that can bring nations to their knees, the strategic circumspection of empathic feminine health "worriers" may bring more effective and humanitarian outcomes than the devil-may-care incaution of masculine risk-taking "warriors".

Status does not predict stress: Women in an egalitarian hunter-gatherer society

It is widely believed that there is strong association between physiological stress and an individual's social status in their social hierarchy. This has been claimed for all humans cross-culturally, as well as in non-human animals living in social groups. However, the relationship between stress and social status has not been explored in any egalitarian hunter-gatherer society; it is also under investigated in exclusively female social groups. Most of human evolutionary history was spent in small, mobile foraging bands of hunter-gatherers with little economic differentiation - egalitarian societies. We analysed women's hair cortisol concentration along with two domains of women's social status (foraging reputation and popularity) in an egalitarian hunter-gatherer society, the Hadza. We hypothesized that higher social status would be associated with lower physiological indicators of stress in these women. Surprisingly, we did not find any association between either foraging reputation or popularity and hair cortisol concentration. The results of our study suggest that social status is not a consistent or powerful predictor of physiological stress levels in women in an egalitarian social structure. This challenges the notion that social status has the same basic physiological implications across all demographics and in all human societies.

Mother's social status is associated with child health in a horticulturalist population

High social status is often associated with greater mating opportunities and fertility for men, but do women also obtain fitness benefits of high status? Greater resource access and child survivorship may be principal pathways through which social status increases women's fitness. Here, we examine whether peer-rankings of women's social status (indicated by political influence, project leadership, and respect) positively covaries with child nutritional status and health in a community of Amazonian horticulturalists. We find that maternal political influence is associated with improved child health outcomes in models adjusting for maternal age, parental height and weight, level of schooling, household income, family size, and number of kin in the community. Children of politically influential women have higher weight-for-age (B = 0.33; 95% CI = 0.12-0.54), height-for-age (B = 0.32; 95% CI = 0.10-0.54), and weight-for-height (B = 0.24; 95% CI = 0.04-0.44), and they are less likely to be diagnosed with common illnesses (OR = 0.48; 95% CI = 0.31-0.76). These results are consistent with women leveraging their social status to enhance reproductive success through improvements in child health. We discuss these results in light of parental investment theory and the implications for the evolution of female social status in humans.

Contest versus scramble competition: sex differences in the quest for status

Both sexes benefit from attaining higher status than same-sex peers, but each sex employs distinctive competitive tactics. Men engage in conspicuous public contests for status and directly interfere with others' success. Despite frequent and intense contests which occasionally turn lethal, men typically employ ritualized tactics and accept status differentials within a group. More recently, research has examined women's subtle, safe, and often solitary, competitive tactics. Women's main competitive tactics consist of maintaining a few long-term alliances and gaining advantages when competitors are not present. When competitors are present, women utilize leveling, social exclusion, and low-cost forms of contest competition to best other women.

Closing the gender gap in competitiveness through priming

Men have been observed to have a greater willingness to compete compared to women, and it is possible that this contributes to gender differences in wages and career advancement. Policy interventions such as quotas are sometimes used to remedy this but these may cause unintended side-effects. Here, we present experimental evidence that a simple and practically costless tool—priming subjects with power—can close the gender gap in competitiveness. While in a neutral as well as in a low-power priming situation men are much more likely than women to choose competition, this gap vanishes when subjects are primed with a high-power situation. We show that priming with high power makes competition entry decisions more realistic and also that it reduces the level of risk tolerance among male participants, which can help explain why it leads to a closing down of the gender gap in competitiveness.

Men are often more willing to compete compared to women, which may contribute to gender differences in wages and career advancement. Here, the authors show that ‘power priming’ - encouraging people to imagine themselves in a situation of power - can close the gender gap in competitiveness.

Sex differences in political leadership in an egalitarian society

We test the contribution of sex differences in physical formidability, education, and cooperation to the acquisition of political leadership in a small-scale society. Among forager-farmers from the Bolivian Amazon, we find that men are more likely to exercise different forms of political leadership, including verbal influence during community meetings, coordination of community projects, and dispute resolution. We show that these differences in leadership are not due to gender per se but are associated with men's greater number of cooperation partners, greater access to schooling, and greater body size and physical strength. Men's advantage in cooperation partner number is tied to their participation in larger groups and to the opportunity costs of women's intrahousehold labor. We argue these results highlight the mutual influence of sexual selection and the sexual division of labor in shaping how women and men acquire leadership.