The Myth of Man the Hunter: Women's contribution to the hunt across ethnographic contexts

Synthesis of sexual selection: a systematic map of meta-analyses with bibliometric analysis

Sexual selection has been a popular subject within evolutionary biology because of its central role in explaining odd and counterintuitive traits observed in nature. Consequently, the literature associated with this field of study became vast. Meta-analytical studies attempting to draw inferences from this literature have now accumulated, varying in scope and quality, thus calling for a synthesis of these syntheses. We conducted a systematic literature search to create a systematic map with a report appraisal of meta-analyses on topics associated with sexual selection, aiming to identify the conceptual and methodological gaps in this secondary literature. We also conducted bibliometric analyses to explore whether these gaps are associated with the gender and origin of the authors of these meta-analyses. We included 152 meta-analytical studies in our systematic map. We found that most meta-analyses focused on males and on certain animal groups (e.g. birds), indicating severe sex and taxonomic biases. The topics in these studies varied greatly, from proximate (e.g. relationship of ornaments with other traits) to ultimate questions (e.g. formal estimates of sexual selection strength), although the former were more common. We also observed several common methodological issues in these studies, such as lack of detailed information regarding searches, screening, and analyses, which ultimately impairs the reliability of many of these meta-analyses. In addition, most of the meta-analyses' authors were men affiliated to institutions from developed countries, pointing to both gender and geographical authorship biases. Most importantly, we found that certain authorship aspects were associated with conceptual and methodological issues in meta-analytical studies. Many of our findings might simply reflect patterns in the current state of the primary literature and academia, suggesting that our study can serve as an indicator of issues within the field of sexual selection at large. Based on our findings, we provide both conceptual and analytical recommendations to improve future studies in the field of sexual selection.

Exploring Within-Gender Differences in Friendships Using an Online Social Network

People tend to befriend others similar to themselves, generating a pattern called homophily. However, existing studies on friendship patterns often rely on surveys that assess the perspective of relatively few participants on their friendships but do not measure actualized friendship patterns. Here, we used data from a large Slovakian online social network to assess the role of gender, age, and body mass index (BMI) in same-gender online connections among more than 400,000 users. We found that age and BMI homophily occurred in both men's and women's same-gender connections, but somewhat more strongly among men's. Yet, as women diverged in BMI, their connections were less likely to be reciprocated. We discuss how the evolutionary legacy of men's coalitional competition (e.g., warfare) and women's mating competition or recruitment of allocare providers might contribute to these patterns in modern same-gender relationships. For example, men's engagement in physical activities may lead to similar formidability levels among their same-gender peers. Altogether, our findings highlight the importance of trait similarity to same-gender friendship patterns.

Human behaviors driving disease emergence

Interactions between humans, animals, and the environment facilitate zoonotic spillover-the transmission of pathogens from animals to humans. Narratives that cast modern humans as exogenous and disruptive forces that encroach upon "natural" disease systems limit our understanding of human drivers of disease. This review leverages theory from evolutionary anthropology that situates humans as functional components of disease ecologies, to argue that human adaptive strategies to resource acquisition shape predictable patterns of high-risk human-animal interactions, (2) humans construct ecological processes that facilitate spillover, and (3) contemporary patterns of epidemiological risk are emergent properties of interactions between human foraging ecology and niche construction. In turn, disease ecology serves as an important vehicle to link what some cast as opposing bodies of theory in human ecology. Disease control measures should consider human drivers of disease as rational, adaptive, and dynamic and capitalize on our capacity to influence ecological processes to mitigate risk.

Remembering the null hypothesis when searching for brain sex differences

Human brain sex differences have fascinated scholars for centuries and become a key focus of neuroscientists since the dawn of MRI. We recently published a major review in Neuroscience and Biobehavioral Reviews showing that most male-female brain differences in humans are small and few have been reliably replicated. Although widely cited, this work was the target of a critical Commentary by DeCasien et al. (Biol Sex Differ 13:43, 2022). In this response, I update our findings and confirm the small effect sizes and pronounced scatter across recent large neuroimaging studies of human sex/gender difference. Based on the sum of data, neuroscientists would be well-advised to take the null hypothesis seriously: that men and women's brains are fundamentally similar, or "monomorphic". This perspective has important implications for how we study the genesis of behavioral and neuropsychiatric gender disparities.

Muscle activity during crouched walking

OBJECTIVES

Muscle activity during crouched walking has been previously studied in the context of the evolution of hominin bipedalism and human movement disorders. However, crouched walking could also be used in approach hunting where postural height (actual height of the body from the ground to the top of the head during locomotion) is the limiting factor. Here, we aim to analyze the relationship between relative postural height (%stature), kinematics, and muscle activity during crouched walking.

MATERIALS AND METHODS

Adult males (n = 19) walked with extended limbs and at three degrees of crouch while their 3D motion capture kinematics and lower limb muscle electromyography were recorded. We measured activation of tibialis anterior, soleus, gastrocnemius medialis, gastrocnemius lateralis, vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus. We analyzed the effects of postural height on kinematics and muscle activation using linear mixed effects model.

RESULTS

Flexion angles, individual muscle activation (except for medial gastrocnemius), and total muscle activation were negatively related to relative postural height, that is, were greater at more crouched postures. Relative postural height had a stronger effect on the activation of the thigh and gluteal muscles compared to shank muscles.

DISCUSSION

General increase in lower limb muscle activation at lower postural heights suggests a negative relationship between relative postural height and fatigue, and may indicate a possible mechanism by which short stature could benefit the hunter in approach hunting. Greater activation of thigh and gluteal muscles relative to shank muscles may help to identify crouched walking in past human populations.

Lithic usewear confirms the function of Wilamaya Patjxa projectile points

Approximately 9000 years ago at the Andean highland site of Wilamaya Patjxa, forager communities interred female and male individuals with projectile points, suggesting that large-mammal hunting may have been a gender neutral activity among that community. We report a lithic usewear analysis, which confirms that the ostensible projectile points were indeed used as projectile points. The data further reveal evidence of cutting and hide scraping consistent with animal processing activities. A new radiocarbon date shows that the female and male individuals were contemporaries, or nearly so, sometime between 9.0 and 8.7 cal. ka. These findings support a model of early subsistence practices in which both female and male individuals at Wilamaya Patjxa hunted large mammals.

Evidence of the active participation of women in the intergroup conflict based on the use of aggression and cooperation

Intergroup conflict has been a persistent aspect of human societies since the emergence of our species. Various researchers have proposed that competition between groups has acted as a key selective force throughout human evolutionary history. Such intergroup competition for limited resources exacerbated the expression of intergroup aggression and intragroup cooperation. Furthermore, it would have a sexual dimorphism, with men demonstrating increased sensitivity to conflict threats-in order to maximize reproductive opportunities-, while women generally reject from active engagement in intergroup conflict. In the present study, we conducted behavioral experiments under controlled laboratory conditions to measure cooperation and aggression from using virtual games, specifically the Public Good Games and the Point Subtraction Aggression Paradigm, in a sample of 541 participants. We created control and experimental intergroup competition scenarios, where aggression and cooperation were necessary to increase monetary rewards. Our results shows that men modulate aggression and cooperation in the presence of intergroup conflict. In addition, our data also reveals that women cooperate more than men and display heightened levels of cooperation and aggression when confronted with intergroup conflict. These findings prompt a reevaluation of current functional theoretical models concerning the role of women in intergroup conflict and suggest that the dynamics of human aggression and cooperation may be more nuanced than previously believed.

On the utility of Colour in shape analysis: An introduction to Colour science via palaeographical case studies

In this article, we explore the use of colour for the analysis of shapes in digital images. We argue that colour can provide unique information that is not available from shape alone, and that familiarity with the interdisciplinary field of colour science is essential for unlocking the potential of colour. Within this perspective, we offer an illustrated overview of the colour-related aspects of image management and processing, perceptual psychology, and cultural studies, using for exemplary purposes case studies focused on computational palaeography. We also discuss the changing roles of colour in society and the sciences, and provide technical solutions for using digital colour effectively, highlighting the impact of human factors. The article concludes with an annotated bibliography. This work is a primer, and its intended readership are scholars and computer scientists unfamiliar with colour science.

Atlatl use equalizes female and male projectile weapon velocity

The atlatl is a handheld, rod-shaped device that employs leverage to launch a dart, and represents a major human technological innovation. One hypothesis for forager atlatl adoption over its presumed predecessor, the thrown javelin, is that a diverse array of people could achieve equal performance results, thereby facilitating inclusive participation of more people in hunting activities. We tested this hypothesis via a systematic assessment of 2160 weapon launch events by 108 people who used both technologies. Our results show that, unlike the javelin, the atlatl equalizes the velocity of female- and male-launched projectiles. This result indicates that a javelin to atlatl transition would have promoted a unification, rather than division, of labor. Moreover, our results suggest that female and male interments with atlatl weaponry should be interpreted similarly.