Sex contextualism in laboratory research: Enhancing rigor and precision in the study of sex-related variables.

Understanding sex-related variation in health and illness requires rigorous and precise approaches to revealing underlying mechanisms. A first step is to recognize that sex is not in and of itself a causal mechanism; rather, it is a classification system comprising a set of categories, usually assigned according to a range of varying traits. Moving beyond sex as a system of classification to working with concrete and measurable sex-related variables is necessary for precision. Whether and how these sex-related variables matter-and what patterns of difference they contribute to-will vary in context-specific ways. Second, when researchers incorporate these sex-related variables into research designs, rigorous analytical methods are needed to allow strongly supported conclusions. Third, the interpretation and reporting of sex-related variation require care to ensure that basic and preclinical research advance health equity for all.

Precision medicine requires understanding how both sex and gender influence health.

Progress in studying sex as a biological variable (SABV) is slow, and the influence of gendered effects of the social environment on biology is largely unknown. Yet incorporating these concepts into basic science research will enhance our understanding of human health and disease. We provide steps to move this process forward.

Sex Differences in Intestinal Carbohydrate Metabolism Promote Food Intake and Sperm Maturation.

Physiology and metabolism are often sexually dimorphic, but the underlying mechanisms remain incompletely understood. Here, we use the intestine of Drosophila melanogaster to investigate how gut-derived signals contribute to sex differences in whole-body physiology. We find that carbohydrate handling is male-biased in a specific portion of the intestine. In contrast to known sexual dimorphisms in invertebrates, the sex differences in intestinal carbohydrate metabolism are extrinsically controlled by the adjacent male gonad, which activates JAK-STAT signaling in enterocytes within this intestinal portion. Sex reversal experiments establish roles for this male-biased intestinal metabolic state in controlling food intake and sperm production through gut-derived citrate. Our work uncovers a male gonad-gut axis coupling diet and sperm production, revealing that metabolic communication across organs is physiologically important. The instructive role of citrate in inter-organ communication might be significant in more biological contexts than previously recognized.

Limbic Neurons Shape Sex Recognition and Social Behavior in Sexually Naive Males.

Sexually naive animals have to distinguish between the sexes because they show species-typical interactions with males and females without meaningful prior experience. However, central neural pathways in naive mammals that recognize sex of other individuals remain poorly characterized. We examined the role of the principal component of the bed nucleus of stria terminalis (BNSTpr), a limbic center, in social interactions in mice. We find that activity of aromatase-expressing BNSTpr (AB) neurons appears to encode sex of other animals and subsequent displays of mating in sexually naive males. Silencing these neurons in males eliminates preference for female pheromones and abrogates mating success, whereas activating them even transiently promotes male-male mating. Surprisingly, female AB neurons do not appear to control sex recognition, mating, or maternal aggression. In summary, AB neurons represent sex of other animals and govern ensuing social behaviors in sexually naive males.

Host and Environmental Factors Influencing Individual Human Cytokine Responses.

Differences in susceptibility to immune-mediated diseases are determined by variability in immune responses. In three studies within the Human Functional Genomics Project, we assessed the effect of environmental and non-genetic host factors of the genetic make-up of the host and of the intestinal microbiome on the cytokine responses in humans. We analyzed the association of these factors with circulating mediators and with six cytokines after stimulation with 19 bacterial, fungal, viral, and non-microbial metabolic stimuli in 534 healthy subjects. In this first study, we show a strong impact of non-genetic host factors (e.g., age and gender) on cytokine production and circulating mediators. Additionally, annual seasonality is found to be an important environmental factor influencing cytokine production. Alpha-1-antitrypsin concentrations partially mediate the seasonality of cytokine responses, whereas the effect of vitamin D levels is limited. The complete dataset has been made publicly available as a comprehensive resource for future studies. PAPERCLIP.

Political organization and gender predict violence in the Andean archaeological record.

The relationship between sociopolitical organization and violence remains an enduring question in anthropological research. Less studied is the articulation of gender with violence in societies of different sociopolitical organization. We investigate the frequency and type of violence experienced by adult males and females in pre-Hispanic Andean archaeological contexts, comparing exposure to antemortem (nonlethal) and perimortem (potentially lethal) violence across three categories of sociopolitical organization: autonomous communities, regional cultural formations, and states. Using a database of 8,607 adults from 169 publications and over 155 sites, we construct a multinomial logistic regression using Bayesian Hamiltonian Monte Carlo methods to fit our model. The odds of antemortem and perimortem trauma were low for both sexes. However, the odds of antemortem trauma were consistently higher for males than females in all categories of sociopolitical organization, suggesting that men were more frequently exposed to violence. Males display similar odds of cranial trauma across all forms of sociopolitical organization, while females display slightly reduced odds of cranial trauma in states compared to autonomous communities. Perimortem trauma is especially strongly patterned by sex. In autonomous communities, the odds of potentially lethal cranial trauma are equivalent between the sexes; in states, they are consistent for males, but depressed for females. In the pre-Hispanic Andes, living in states dramatically reduced the chances of encountering lethal violence for females, but not males. Our study complicates the notion that increasing sociopolitical complexity leads to decreasing interpersonal violence and highlights the importance of gender in understanding the human history of violence.

Is gender primacy universal?

Emerging evidence suggests that gender is a defining feature of personhood. Studies show that gender is the primary social category individuals use to perceive humanness and the social category most strongly related to seeing someone-or something-as human. However, the universality of gender's primacy in social perception and its precedence over other social categories like race and age have been debated. We examined the primacy of gender perception in the Mayangna community of Nicaragua, a population with minimal exposure to Western influences, to test whether the primacy of gender categorization in humanization is more likely to be a culturally specific construct or a cross-cultural and potentially universal phenomenon. Consistent with findings from North American populations [A. E. Martin, M. F. Mason, J. Pers. Soc. Psychol. 123, 292-315 (2022)], the Mayangna ascribed gender to nonhuman objects more strongly than any other social category-including age, race, sexual orientation, disability, and religion-and gender was the only social category that uniquely predicted perceived humanness (i.e., the extent to which a nonhuman entity was seen as "human"). This pattern persisted even in the most isolated subgroup of the sample, who had no exposure to Western culture or media. The present results thus suggest that gender's primacy in social cognition is a widely generalizable, and potentially universal, phenomenon.

The gender agency gap in fiction writing (1850 to 2010).

Works of fiction play a crucial role in the production of cultural stereotypes. Concerning gender, a widely held presumption is that many such works ascribe agency to men and passivity to women. However, large-scale diachronic analyses of this notion have been lacking. This paper provides an assessment of agency attributions in 87,531 fiction works written between 1850 and 2010. It introduces a syntax-based approach for extracting networks of character interactions. Agency is then formalized as a dyadic property: Does a character primarily serve as an agent acting upon the other character or as recipient acted upon by the other character? Findings indicate that female characters are more likely to be passive in cross-gender relationships than their male counterparts. This difference, the gender agency gap, has declined since the 19th century but persists into the 21st. Male authors are especially likely to attribute less agency to female characters. Moreover, certain kinds of actions, especially physical and villainous ones, have more pronounced gender disparities.

Gender gaps at the academies.

Historically, a large majority of newly elected members of the National Academy of Science (NAS) and the American Academy of Arts and Science (AAAS) were men. Within the past two decades, however, that situation has changed, and in the last 3 y, women made up about 40% of the new members in both academies. We build lists of active scholars from publications in the top journals in three fields-psychology, mathematics, and economics-and develop a series of models to compare changes in the probability of selection of women as members of the NAS and AAAS from the 1960s to today, controlling for publications and citations. In the early years of our sample, women were less likely to be selected as members than men with similar records. By the 1990s, the selection process at both academies was approximately gender neutral, conditional on publications and citations. In the past 20 y, however, a positive preference for female members has emerged and strengthened in all three fields. Currently, women are 3 to 15 times more likely to be selected as members of the AAAS and NAS than men with similar publication and citation records. The positive preference for women may be in part a reflection of concerns that women face higher barriers to publishing in top journals and may receive less credit for their work.

Gender bias in teaching evaluations: the causal role of department gender composition.

Women are underrepresented in academia's higher ranks. Promotion oftentimes requires positive student-provided course evaluations. At a U.S. university, both an archival and an experimental investigation uncovered gender discrimination that affected both men and women. A department's gender composition and the course levels being taught interacted to predict biases in evaluations. However, women were disproportionately impacted because women were more often in the gender minority. A subsequent audit of the university's promotion guidelines suggested a disproportionate impact on women's career trajectories. Our framework was guided by role congruity theory, which poses that workplace positions are gendered by the ratios of men and women who fill them. We hypothesized that students would expect educators in a department's gender majority to fill more so essential positions of teaching upper-level courses and those in the minority to fill more so supportive positions of teaching lower-level courses. Consistent with role congruity theory when an educator's gender violated expected gendered roles, we generally found discrimination in the form of lower evaluation scores. A follow-up experiment demonstrated that it was possible to change students' expectations about which gender would teach their courses. When we assigned students randomly to picture themselves as students in a male-dominated, female-dominated, or gender-parity department, we shifted their expectations of whether men or women would teach upper- and lower-level courses. Violating students' expectations created negative biases in teaching evaluations. This provided a causal link between department gender composition and discrimination. The importance of gender representation and ameliorating strategies are discussed.

Persistence of gender biases in Europe.

Prior work suggests that modern gender bias might have historical roots but has not been able to demonstrate long-term persistence of this bias due to a lack of historical data. We follow archaeological research and employ skeletal records of women's and men's health from 139 archaeological sites in Europe dating back, on average, to about 1200 AD to construct a site-level indicator of historical bias in favor of one gender over the other using dental linear enamel hypoplasias. This historical measure of gender bias significantly predicts contemporary gender attitudes, despite the monumental socioeconomic and political changes that have taken place since. We also show that this persistence is most likely due to the intergenerational transmission of gender norms, which can be disrupted by significant population replacement. Our results demonstrate the resilience of gender norms and highlight the importance of cultural legacies in sustaining and perpetuating gender (in)equality today.

Girls' comparative advantage in language arts explains little of the gender gap in math-related fields: A replication and extension.

Women remain underrepresented in most math-intensive fields. [Breda and Napp, Proc. Natl. Acad. Sci. U.S.A. 116, 15435 (2019)] reported that girls' comparative advantage in reading over math (i.e., the intraindividual differences between girls' reading vs. math performance, compared to such differences for boys) could explain up to 80% of the gender gap in students' intentions to pursue math-intensive studies and careers, in conflict with findings from previous research. We conducted a conceptual replication and expanded upon Breda and Napp's study by using new global data (PISA2018, N = 466,165) and a recent US nationally representative longitudinal study (High School Longitudinal Study of 2009, N = 6,560). We coded students' intended majors and careers and their actual college majors. The difference between a student's math vs. reading performance explained only small proportions of the gender gap in students' intentions to pursue math-intensive fields (0.4 to 10.2%) and in their enrollment in math-intensive college majors (12.3%). Consistent with previous studies, our findings suggest girls' comparative advantage in reading explains a minority of the gender gap in math-related majors and occupational intentions and choices. Potential reasons for differences in the estimated effect sizes include differences in the operationalization of math-related choices, the operationalization of math and reading performance, and possibly the timing of measuring intentions and choices. Therefore, it seems premature to conclude that girls' comparative advantage in reading, rather than the cumulative effects of other structural and/or psychological factors, can largely explain the persistent gender gap in math-intensive educational and career choices.

Large motherhood penalties in US administrative microdata.

Whereas previous research has described motherhood penalties in US survey data, we leverage administrative data on 811,000 quarterly earnings histories from the US Unemployment Insurance program. We analyze contexts where smaller motherhood penalties might be expected: couples where the woman outearns her male partner prior to childbearing, at firms that are headed by women, and at firms that are predominantly women. Our startling result is that none of these propitious contexts appear to diminish the motherhood penalty, and indeed, the gap often increases in magnitude over time following childbearing. We estimate one of the largest motherhood penalties in "female-breadwinner" families, where higher-earning women experience a 60% drop from their prechildbirth earnings relative to their male partners. Turning to proximate mechanisms, women are less likely to switch to a higher-paying firm postchildbearing than men and are substantially more likely to quit the labor force. On the whole, our findings are discouraging relative even to existing research on motherhood penalties.

A critical analysis of plant science literature reveals ongoing inequities.

The field of plant science has grown dramatically in the past two decades, but global disparities and systemic inequalities persist. Here, we analyzed ~300,000 papers published over the past two decades to quantify disparities across nations, genders, and taxonomy in the plant science literature. Our analyses reveal striking geographical biases-affluent nations dominate the publishing landscape and vast areas of the globe have virtually no footprint in the literature. Authors in Northern America are cited nearly twice as many times as authors based in Sub-Saharan Africa and Latin America, despite publishing in journals with similar impact factors. Gender imbalances are similarly stark and show remarkably little improvement over time. Some of the most affluent nations have extremely male biased publication records, despite supposed improvements in gender equality. In addition, we find that most studies focus on economically important crop and model species, and a wealth of biodiversity is underrepresented in the literature. Taken together, our analyses reveal a problematic system of publication, with persistent imbalances that poorly capture the global wealth of scientific knowledge and biological diversity. We conclude by highlighting disparities that can be addressed immediately and offer suggestions for long-term solutions to improve equity in the plant sciences.

Part of the gender gap in voting for Democrats arises because a higher proportion of women than men voters are Black.

Women voted for the Democratic candidate more than men did in each US presidential election since 1980. We show that part of the gender gap stems from the fact that a higher proportion of women than men voters are Black, and Black voters overwhelmingly choose Democratic candidates. Past research shows that Black men have especially high rates of death, incarceration, and disenfranchisement due to criminal convictions. These disparities reduce the share of men voters who are Black. We show that the gender difference in racial composition explains 24% of the gender gap in voting Democratic. The gender gap in voting Democratic is especially large among those who are never-married, and, among them, the differing racial composition of men and women voters is more impactful than in the population at large, explaining 43% of the gender gap. We consider an alternative hypothesis that income differences between single men and women explain the gender gap in voting, but our analysis leads us to reject it. Although unmarried women are poorer than unmarried men, and lower-income voters vote slightly more Democratic, the latter difference is too small for income to explain much of the gender gap in voting. In short, the large gender gap among unmarried voters is not a reflection of the lower incomes of women's households but does reflect the fact that women voters are disproportionately Black. We used the General Social Survey as the data source for the analysis, then replicated results with the American National Election Survey data.

The gender gap in the ownership of promising land.

Using millions of observations compiled from the public administrative data of Taiwan, we find a surprising gender inequity in terms of real estate: Men own more land than women, and the annual rate of return (ROR) of men's land outperform women's by almost 1% per year. The latter finding of gender-based ROR difference is in sharp contrast to prior evidence that women outperform men in security investment, and also suggests a quantity-and-quality double jeopardy in female land ownership which, given the heavy weight of real estate in individual wealth, has important implications for wealth inequality among men and women. Our statistical analyses suggest that such a gender-based difference in land ROR cannot be attributed to individual-level factors such as liquidity preferences, risk attitudes, investment experience, and behavioral biases, as described in the literature. Rather, we hypothesize parental gender bias-a phenomenon that is still prevalent today-to be the key macrolevel factor. To test our hypothesis, we partition our observations into two groups: an experimental group in which parents can exercise gender discretion, and a control group in which parents cannot exercise such discretion. Our empirical evidence shows that the gender difference with respect to land ROR only exists in the experimental group. For many societies with long-lasting patriarchal traditions, our analysis provides a perspective to help explain gender differences in wealth distribution and social mobility.

Country-level gender inequality is associated with structural differences in the brains of women and men.

Gender inequality across the world has been associated with a higher risk to mental health problems and lower academic achievement in women compared to men. We also know that the brain is shaped by nurturing and adverse socio-environmental experiences. Therefore, unequal exposure to harsher conditions for women compared to men in gender-unequal countries might be reflected in differences in their brain structure, and this could be the neural mechanism partly explaining women's worse outcomes in gender-unequal countries. We examined this through a random-effects meta-analysis on cortical thickness and surface area differences between adult healthy men and women, including a meta-regression in which country-level gender inequality acted as an explanatory variable for the observed differences. A total of 139 samples from 29 different countries, totaling 7,876 MRI scans, were included. Thickness of the right hemisphere, and particularly the right caudal anterior cingulate, right medial orbitofrontal, and left lateral occipital cortex, presented no differences or even thicker regional cortices in women compared to men in gender-equal countries, reversing to thinner cortices in countries with greater gender inequality. These results point to the potentially hazardous effect of gender inequality on women's brains and provide initial evidence for neuroscience-informed policies for gender equality.

Self-esteem trajectories over three decades predict opposition to social equality in midlife.

Although life trajectories are frequently theorized to explain people's attitudes toward different social groups, few studies have been able to directly assess their importance with suitable data. Addressing this gap and focusing on the development of general and domain-specific self-esteem, we report results from a population-based sample of Norwegians (N = 2,215) followed over 28 years and five time points from adolescence to midlife. Growth curve models demonstrated that irrespective of self-esteem domain, low levels of self-esteem in adolescence as well as a depressed self-esteem development over the next three decades were related to more overall opposition to social equality as well as more opposition to gender equality and immigration in midlife. The results held when controlling for participants' baseline political orientations and other key covariates in adolescence. Our findings indicate that low self-esteem and a lack of positive self-esteem development can be detrimental to harmonious intergroup relations in ever-diversifying societies. We discuss how future psychological interventions aimed at enhancing self-esteem may promote support for a more inclusive society.

Data-driven approaches can harness crop diversity to address heterogeneous needs for breeding products.

This perspective describes the opportunities and challenges of data-driven approaches for crop diversity management (genebanks and breeding) in the context of agricultural research for sustainable development in the Global South. Data-driven approaches build on larger volumes of data and flexible analyses that link different datasets across domains and disciplines. This can lead to more information-rich management of crop diversity, which can address the complex interactions between crop diversity, production environments, and socioeconomic heterogeneity and help to deliver more suitable portfolios of crop diversity to users with highly diverse demands. We describe recent efforts that illustrate the potential of data-driven approaches for crop diversity management. A continued investment in this area should fill remaining gaps and seize opportunities, including i) supporting genebanks to play a more active role in linking with farmers using data-driven approaches; ii) designing low-cost, appropriate technologies for phenotyping; iii) generating more and better gender and socioeconomic data; iv) designing information products to facilitate decision-making; and v) building more capacity in data science. Broad, well-coordinated policies and investments are needed to avoid fragmentation of such capacities and achieve coherence between domains and disciplines so that crop diversity management systems can become more effective in delivering benefits to farmers, consumers, and other users of crop diversity.

A gender perspective on the global migration of scholars.

Although considerable progress toward gender equality in science has been made in recent decades, female researchers continue to face significant barriers in the academic labor market. International mobility has been increasingly recognized as a strategy for scientists to expand their professional networks, and that could help narrow the gender gap in academic careers. Using bibliometric data on over 33 million Scopus publications, we provide a global and dynamic view of gendered patterns of transnational scholarly mobility, as measured by volume, distance, diversity, and distribution, from 1998 to 2017. We find that, while female researchers continued to be underrepresented among internationally mobile researchers and migrate over shorter distances, this gender gap was narrowing at a faster rate than the gender gap in the population of general active researchers. Globally, the origin and destination countries of both female and male mobile researchers became increasingly diversified, which suggests that scholarly migration has become less skewed and more globalized. However, the range of origin and destination countries continued to be narrower for women than for men. While the United States remained the leading academic destination worldwide, the shares of both female and male scholarly inflows to that country declined from around 25% to 20% over the study period, partially due to the growing relevance of China. This study offers a cross-national measurement of gender inequality in global scholarly migration that is essential for promoting gender-equitable science policies and for monitoring the impact of such interventions.