Human Nature

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I present a detailed ethnographic study of magic and divination of the Nuosu people in southwest China and offer a cognitive account of the surprising prevalence of these objectively ineffective practices in a society that has ample access to modern technology and mainstream Han culture. I argue that in the belief system of the Nuosu, ghosts, divination, and magical healing rituals form a closely interconnected web that gives sense and meaning to otherwise puzzling practices, and such a belief system is importantly supported and reinforced by individual’s everyday experiences. Contemporary Nuosu people overwhelmingly treat these practices as instruments for achieving specific ends and often entertain considerable uncertainty regarding their efficacy, which may be overestimated for a number of reasons, including the following: (1) the intuitive plausibility of divination for ghost identification and exorcist rituals is enhanced by the belief in the existence of ghosts as a result of abductive reasoning, (2) negative instances (divinatory or healing ritual failures) are underreported, and (3) people’s misperception of the probability of uncertain events’ occurrence often prevents them from realizing that the efficacies of magical/divinatory practices do not outperform chance. I conclude with some comments on the generalizability of the psychological and social mechanisms discussed.
 
Plot (a) shows London’s mean daily temperature in 2000, along with two polynomial models fitted using the least squares method. The first is a degree-3 polynomial with 4 parameters (the simpler model), and the second is a degree-12 polynomial with 13 parameters (the more complex model). Plot (b) shows both the mean error in fitting samples of 30 observations (the training data), and the mean predictive error of the same models against the test data, both as a function of degree of polynomial. Figure and modified caption from Brighton and Gigerenzer (2012:Fig. 1, licensed under Creative Commons)
The bias-variance trade-off. Simpler models have more bias but less variance, and therefore often have less total error
Proportion of 115 magico-religious practitioners in the Human Relations Area Files with various traits. Practitioners could have multiple traits.
Adapted from Winkelman (1984)
A data-driven taxonomy of medicinal specialists in 47 cultures derived from ethnographic text records in the Human Relations Area Files. This minimum spanning tree estimates the similarities of binary presence/absence data for each of the coded variables (vertices) in the cross-cultural dataset. Vertex sizes correspond to levels of text record evidence for each variable. Edge lengths represent binary distances between variables. Colors refer to our interpretations of each branch in the taxonomy of medicinal specialists.
Adapted from Lightner et al. (2021a)
Examples of the proposed domains of important socially and individually learned information. Top: Infrequent situations are the focus of religious and other knowledge specialists. Bottom: Common situations are the focus of most individuals in the general population. Left: Games against nature. Right: Games against others
Many cognitive and evolutionary theories of religion argue that supernatural explanations are byproducts of our cognitive adaptations. An influential argument states that our supernatural explanations result from a tendency to generate anthropomorphic explanations, and that this tendency is a byproduct of an error management strategy because agents tend to be associated with especially high fitness costs. We propose instead that anthropomorphic and other supernatural explanations result as features of a broader toolkit of well-designed cognitive adaptations, which are designed for explaining the abstract and causal structure of complex, unobservable, and uncertain phenomena that have substantial impacts on fitness. Specifically, we argue that (1) mental representations about the abstract vs. the supernatural are largely overlapping, if not identical, and (2) when the data-generating processes for scarce and ambiguous observations are complex and opaque, a naive observer can improve a bias-variance trade-off by starting with a simple, underspecified explanation that Western observers readily interpret as “supernatural.” We then argue that (3) in many cases, knowledge specialists across cultures offer pragmatic services that involve apparently supernatural explanations, and their clients are frequently willing to pay them in a market for useful and effective services. We propose that at least some ethnographic descriptions of religion might actually reflect ordinary and adaptive responses to novel problems such as illnesses and natural disasters, where knowledge specialists possess and apply the best available explanations about phenomena that would otherwise be completely mysterious and unpredictable.
 
Relationship between current frequency p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p$$\end{document} and change in frequency p′-p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${p}^{^{\prime}}-p$$\end{document} (p′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${p}^{^{\prime}}$$\end{document} denotes the frequency in the next generation) under different parameter combinations. b1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${b}_{1}$$\end{document} is fixed at 1, σ2=0.1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\upsigma }^{2}=0.1$$\end{document} (the variance for the payoff error term in agent-based simulation), and both wn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${w}_{n}$$\end{document} and wb\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${w}_{b}$$\end{document} are set to be 1. Analytic computation and agent-based simulation are represented by black solid lines and red dotted lines, respectively, and the approximated equilibrium values according to Eq. (5), (b1b1+b2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\frac{{b}_{1}}{{b}_{1}+{b}_{2}}$$\end{document}) is marked by dotted blue lines
Relationship between current frequency p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p$$\end{document} and change in frequency p′-p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${p}^{^{\prime}}-p$$\end{document} in the presence of conformist bias (D>0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$D>0$$\end{document}), anticonformist bias (D<0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$D<0$$\end{document}), or unbiased frequency-dependent transmission (D=0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$D=0$$\end{document}) under different parameter combinations. b1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${b}_{1}$$\end{document} is fixed at 1, and both wn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${w}_{n}$$\end{document} and wb\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${w}_{b}$$\end{document} are set to be 1. The reference line y=0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$y=0$$\end{document} is marked by the solid blue line. All values are computed according to Eq. (7)
Temporal evolutionary trajectories of C1 frequency as well as weight on frequency information (wn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${w}_{n}$$\end{document}) and the magnitude of conformist bias (D\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{D}$$\end{document}) under various payoff conditions (average of 2000 independent simulations). σi2=0.3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\upsigma }_{i}^{2}=0.3$$\end{document}, σ2=0.1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\upsigma }^{2}=0.1$$\end{document}, N=1000\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{N}=1000$$\end{document}, and number of traits each agent possesses = 20 (e.g., each agent needs to make 20 independent variant adoption decisions, with new variants introduced every 10 generation). Dotted lines are reference lines (y=0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{y}=0$$\end{document}). Other parameter values are specified in the ESM
Most research on transmission biases in cultural evolution has treated different biases as distinct strategies. Here I present a model that combines both frequency dependent bias (including conformist bias) and payoff bias in a single decision-making calculus and show that such an integrated learning strategy may be superior to relying on either bias alone. Natural selection may operate on humans’ relative dependence on frequency and payoff information, but both are likely to contribute to the spread of variants with high payoffs. Importantly, the magnitude of conformist bias affects the evolutionary dynamics, and I show that an intermediate level of conformity may be most adaptive and may spontaneously evolve as it resists the invasion of low-payoff variants yet enables the fixation of high-payoff variants in the population.
 
Examples of the five instructions we gave to participants for dataset 1: (1) Make a drawing with scribbles; (2) Make a drawing with circles; (3) Make a drawing with different angles; (4) Make a drawing with a starry sky; (5) Make a drawing with fan patterns
correlation chart of the 14 metrics for dataset 1. The diagonal of the graph provides the distribution of each metric; the bottom left and top right provide the correlation figure and the correlation coefficient, respectively, between two metrics. Statistical value is given with the correlation coefficient: * p < 0.05, ** p < 0.01, and *** p < 0.001
Examples of dataset 1 (third step) drawings (a) according to dimension 1 and dimension 2, as provided by the PCA. Dimension 1 may represent representativeness and dimension 2 may represent diversity. (b) according to dimension 1 and dimension 3, as provided by the PCA. Dimension 1 may represent representativeness and dimension 3 may represent periodicity. (c) according to dimension 2 and dimension 3, as provided by the PCA. Dimension 2 may represent diversity and dimension 3 may represent periodicity
Examples of scribbles for dataset 1 (adults) and dataset 2 (3-year-old children) and boxplot of dimensions 1 to 3 for these two categories
Violin plots representing dimension 1, dimension 2, and dimension 3 across age categories of dataset 2. Violin plots represent the distribution of data, and the black dots represent the mean. Age groups with the same letter belong to the same group according to pairwise comparison tests (see details in ESM).
Figurative drawing is a skill that takes time to learn, and it evolves during different childhood phases that begin with scribbling and end with representational drawing. Between these phases, it is difficult to assess when and how children demonstrate intentions and representativeness in their drawings. The marks produced are increasingly goal-oriented and efficient as the child’s skills progress from scribbles to figurative drawings. Pre-figurative activities provide an opportunity to focus on drawing processes. We applied fourteen metrics to two different datasets (N=65 and N= 344) to better understand the intentional and representational processes behind drawing, and combined these metrics using principal component analysis (PCA) in different biologically significant dimensions. Three dimensions were identified: efficiency based on spatial metrics, diversity with color metrics, and temporal sequentiality. The metrics at play in each dimension are similar for both datasets, and PCA explains 77% of the variance in both datasets. Gender had no effect, but age influenced all three dimensions differently. These analyses for instance differentiate scribbles by children from those drawn by adults. The three dimensions highlighted by this study provide a better understanding of the emergence of intentions and representativeness in drawings. We discussed the perspectives of such findings in comparative psychology and evolutionary anthropology.
 
Example of facial measurements. Eye–mouth–eye angle = a–b–c. Cheekbone prominence = d–e/f–g. Lower face to full face height = i–j/h–j. Facial width to lower face height = d–e/i–j. Image from Chicago Face Database (Ma et al., 2015)
Descriptive statistics of and correlations among dependent variables
Descriptive statistics of and correlations among indices of masculinity for men
We tested the good genes ovulatory shift hypothesis through speed-dating, an ecologically valid paradigm with real life consequences. Fifteen speed-dating sessions of 262 single Asian Americans were held. We analyzed 850 speed-dates involving 132 men and 100 normally ovulating women, finding ovulatory shifts in the desirability of men with more masculine facial measurements (smaller eye–mouth–eye angle, larger lower face to full face height ratio, and smaller facial width to lower face height ratio) in the predicted direction. However, there was no support for ovulatory shifts in preferences for men’s self-reported height. In addition, the expected shifts were not found for women’s second date offers to men. Therefore, with natural stimuli and in a competitive dating scenario, we partially replicated previously documented ovulatory shifts in women’s preferences for men.
 
Boxplots of WAZ, HAZ, and BMIZ. These boxplots illustrate that a substantial majority of children have z-scores below 0.0 on measures of WAZ, HAZ, and BMIZ; the dashed red line indicates the proportion of the sample at or below − 2.0
Venn diagram illustrating children who are underweight (WAZ ≤ − 2 SD) in blue, stunted (HAZ ≤ − 2SD) in purple, and calorically deficient (BMIZ ≤ − 2 SD) in green, in relation to the broader sample (gray). Overlapping areas indicate children deficient in two or more of these measures
Scatterplots of the sibling–polygyny interaction effect on (A) WAZ and (B) HAZ, with estimation values assuming agriculture as primary family occupation and lack of electricity, for polygynous and nonpolygynous families
Mediation model of effects of WAZ, siblings, polygyny, electricity, and agriculture on HAZ. * p < 0.05; **p < 0.01; ***p < 0.001
Weight- (WAZ), height- (HAZ), and BMI-for-age (BMIZ) are frequently used to assess malnutrition among children. These measures represent different categories of risk and are usually hypothesized to be affected by distinct factors, despite their inherent relatedness. Life history theory suggests weight should be sacrificed before height, indicating a demonstrable relationship among them. Here we evaluate impact of family composition and household economics on these measures of nutritional status and explore the role of WAZ as a factor in HAZ. Anthropometrics, family demographics, and measures of household economy were collected from Sidama agropastoralist children in a peri-urban village in southwestern Ethiopia (n = 157; 79 girls). Just over half of the sample (50.9%) had z-scores of − 2SD or below on at least one measure, indicating an elevated risk of morbidity/mortality; 30% were at or below − 2SD on two or more measures. We used hierarchical linear regression with random intercept analysis to model WAZ and HAZ. Siblings and crop sales significantly decrease WAZ while electricity, agriculture, and polygyny improve z-scores; however, an interaction between polygyny and siblings indicates negative effects of siblings in polygynous families and positive effects in nonpolygynous ones (adj. R² = 66.5%). For HAZ, agriculture and electricity are positively associated with z-scores whereas siblings have a negative effect; the interaction term again indicates that effects of siblings vary in polygynous and nonpolygynous families (adj. R² = 74.2%). A mediation model exploring the role of weight in height outcomes suggests not only that WAZ has direct effects on HAZ but also that effects of electricity and agriculture on HAZ are partially mediated by WAZ. Our findings indicate that WAZ and HAZ are primarily affected by shared variables, but effects of siblings vary by polygyny status. Long-term outcomes (HAZ) among Sidama children would likely benefit from interventions focused on stabilizing WAZ across family members.
 
Bar chart of women’s self-reported fasting behavior in previous pregnancies. Green represents women who chose to fast, and red represents women who chose not to fast
Smith’s S scores of free-list data for perceived positive consequences of fasting in pregnancy, divided across the three study populations: Bhubaneshwar Hindus (BH), Mysore Hindus (MH), and Mysore Muslims (MM)
Smith’s S scores of free-list data for perceived negative consequences of fasting in pregnancy, divided across the three study populations: Bhubaneshwar Hindus (BH), Mysore Hindus (MH), and Mysore Muslims (MM)
Fasting during pregnancy is an enigma: why would a woman restrict her food intake during a period of increased nutritional need? Relative to the costs to healthy individuals who are not pregnant, the physiological costs of fasting in pregnancy are amplified, with intrauterine death being one possible outcome. Given these physiological costs, the question arises as to the socioecological factors that give rise to fasting during pregnancy. There has been little formal research regarding the emic perceptions and socioecological factors associated with such fasting. This study therefore took an emic approach and investigated the types of fasts that are common in pregnancy, women’s perceptions of the consequences of fasting, and the socioecological models of pregnancy fasting in three Indian communities. This cross-sectional study took place in Bhubaneshwar, Odisha state, and Mysore, Karnataka state, among two populations of Hindu women and one population of Muslim women (N = 85). In total, 64% of women fasted in prior pregnancies. Findings revealed variation in the number and types of fasts that are common in pregnancy across the three communities. Each community reported differences in positive and negative consequences of fasting, with varied emphasis on reproductive health, religiosity, and general health and well-being. Finally, quantitative analyses indicated that the best-fitting model for fasting during pregnancy was religiosity, and the poorest-fitting models were resource scarcity and general health. This study provides insight into motivations for such fasting and highlights the need to investigate the relationship between supernatural beliefs and maternal–fetal protection further, as well as social functions of pregnancy fasting within the family and community.
 
(A) Predicted bolivianos (the local currency in Bolivia) given by a participant to an out-group stranger as a function of the total estimated value of market items owned by the participant, normalized relative to other participants in the same population (Pisor & Gurven, 2016, 2018). The shaded areas are the 90% credible intervals. Predictions for Intercultural participants are in black, Mosetén in orange, and Tsimane’ in blue. For details on this model, see ESM §1.3. (B) Average bolivianos given by a participant to an out-group stranger (that is, an individual from another pueblo indígena or with a different religious affiliation) in the NAGG (Pisor & Gurven, 2016, 2018). The initial allocation was 3 bolivianos per recipient. Points are jittered
Each participant was asked to name someone who could help them (A) with a loan of 500 bolivianos ($70, or 8 days’ wages) if a flood destroyed their crops, and (B) find “a good job that pays well.” Most participants named individuals, but some named government entities, organizations, or private companies. Counts reflect the distance between the participant and where these named individuals or entities were located
Each participant (n = 125) was presented with a pair of hypothetical individuals and was asked which they preferred as a new friend. Each evaluated 18 pairs of individuals. Here, we present nonstandardized estimates (means and 90% credible regions) from a logistic regression; these estimates reflect the odds of selecting one individual if it were to differ by only a single attribute from the other individual. The base case is a candidate friend who lives in the same community, is from the same pueblo indígena and has the same religious affiliation, and who is not good, not trustworthy, and has no money. The estimates indicate that participants preferred a same-community friend over more distant friends, same-ethnic- and same-religious-group friends over those from other groups, and friends that are “good people,” trustworthy, and—interestingly—not excessively wealthy
Intergroup and long-distance relationships are both central features of human social life, but because intergroup relationships are emphasized in the literature, long-distance relationships are often overlooked. Here, we make the case that intergroup and long-distance relationships should be studied as distinct, albeit related, features of human sociality. First, we review the functions of both kinds of relationship: while both can be conduits for difficult-to-access resources, intergroup relationships can reduce intergroup conflict whereas long-distance relationships are especially effective at buffering widespread resource shortfalls. Second, to illustrate the importance of distinguishing the two relationship types, we present a case study from rural Bolivia. Combining ethnography and two different experimental techniques, we find that the importance of intergroup relationships—and the salience of group membership itself—varies across populations and across methods. Although ethnography revealed that participants often rely on long-distance relationships for resource access, we were unable to capture participant preferences for these relationships with a forced-choice technique. Taken together, our review and empirical data highlight that (1) intergroup and long-distance relationships can have different functions and can be more or less important in different contexts and (2) validating experimental field data with ethnography is crucial for work on human sociality. We close by outlining future directions for research on long-distance relationships in humans.
 
Image-making is a nearly universal human behavior, yet the visual strategies and conventions to represent things in pictures vary greatly over time and space. In particular, pictorial styles can differ in their degree of figurativeness, varying from intersubjectively recognizable representations of things to very stylized and abstract forms. Are there any patterns to this variability, and what might its ecological causes be? Experimental studies have shown that demography and the structure of interaction of cultural groups can play a key role: the greater the degree of contact with other groups, the more recognizable and less abstract are the representations. Here we test this hypothesis on a real-world dataset for the first time. We constructed a balanced database of Indigenous Australian rock art motifs from both isolated and contact Aboriginal groups (those often in contact with other groups). We then ran a survey asking participants to judge the recognizability of the motifs and to provide interpretations. Results show that motifs from contact Aboriginal groups were more likely to be judged as inter-subjectively recognizable and also elicited more convergent descriptions than motifs from isolated groups. This is consistent with the idea that intergroup contact is likely to be an important factor in the cultural evolution of pictorial representation. We discuss the implications of these findings for the archaeology and anthropology of art, and the parallels with language evolution.
 
COVID-19 have an unusual breakout around the end of 2019. Due to lock down situations the online education has become the popular alternative to conventional face to face teaching, yet it comes with some issues and challenges faced by online teachers. The purpose of this study is to investigate the challenges faced by the male and female conventional teachers shifted to online teaching due to this Pandemic. This paper focused on challenges such as pedagogical, technological, time management, online group assessments and lack of interaction. The study conducted using questionnaire survey. A sample of 70 teachers from different university of Lahore, Pakistan was selected. A five point scale questionnaire was developed to collect the data. Frequencies and percentage were used to analyze the overall perception of online teachers about the issues they faced. Independent samples t-test was applied to assess the difference in the perception and experiences of male and female teachers while teaching in an online setting. The correlation analysis was also applied to assess the association among the above-mentioned factors. It was observed that the teachers are mostly facing the pedagogical issues including unfamiliar courses, less visible connection with the students, multitasking and improvements in course contents, time management due to heavy workloads. Only a few teachers are facing technological issues. Most of the teachers found satisfied with the process of assessing the students in online learning. No gender differences were found regarding the issues except that female instructors face more technology-related issues than male. This research provide a baseline to investigate challenges faced by teachers in online space. To address the challenges like Pedagogical, technological, time management, online group assessments and lack of interaction, higher education institutions need to provide training, support and opportunities for the continuous professional development of teachers.
 
African carnivore species (extinct and extant) that overlapped with Homo and other hominins, by body size, habitat, pack hunting, and epoch. Body size ratio is the ratio of the mass of the carnivore relative to that of Homo erectus (46 kg), displayed log-scaled. The gray rectangle indicates the range of body sizes of hominins relative to H. erectus. Data from Treves and Palmqvist (2007)
Extant carnivore maximum sprint speeds, relative to the maximun modern human sprint speed (45 km/hr), by hunting strategy. Data from Hirt et al. (2020)
An image sequenceshowing the propagation of a spiral wave in a colony of giant honeybees (Apis dorsata) (from Kastberger et al., 2008)
After they diverged from panins, hominins evolved an increasingly committed terrestrial lifestyle in open habitats that exposed them to increased predation pressure from Africa’s formidable predator guild. In the Pleistocene, Homo transitioned to a more carnivorous lifestyle that would have further increased predation pressure. An effective defense against predators would have required a high degree of cooperation by the smaller and slower hominins. It is in the interest of predator and potential prey to avoid encounters that will be costly for both. A wide variety of species, including carnivores and apes and other primates, have therefore evolved visual and auditory signals that deter predators by credibly signaling detection and/or the ability to effectively defend themselves. In some cooperative species, these predator deterrent signals involve highly synchronized visual and auditory displays among group members. Hagen and Bryant (Human Nature, 14(1), 21–51, 2003) proposed that synchronized visual and auditory displays credibly signal coalition quality. Here, this hypothesis is extended to include credible signals to predators that they have been detected and would be met with a highly coordinated defensive response, thereby deterring an attack. Within-group signaling functions are also proposed. The evolved cognitive abilities underlying these behaviors were foundations for the evolution of fully human music and dance.
 
Volunteers simulating digging tasks with the help of wooden sticks. Energy expenditure was monitored using an Oxycon Mobile JAEGER.® portable device
Energy expenditure by sex and age group. A Resting metabolic rate (RMR) and B net cost of digging (DIGNet). The vertical bars represent the 95% confidence interval. Age groups: group 1 (from 8 to 10 years old), group 2 (from 11 to 12 years old), and group 3 (from 13 to 14 years old)
Extractive foraging tasks, such as digging, are broadly practiced among hunter-gatherer populations in different ecological conditions. Despite tuber-gathering tasks being widely practiced by children and adolescents, little research has focused on the physical traits associated with digging ability. Here, we assess how age and energetic expenditure affect the performance of this extractive task. Using an experimental approach, the energetic cost of digging to extract simulated tubers is evaluated in a sample of 40 urban children and adolescents of both sexes to measure the intensity of the physical effort and the influence of several anatomical variables. Digging is a moderately vigorous activity for inexperienced girls and boys from 8 to 14 years old, and it requires significant physical effort depending on strength and body size. However, extracting subterranean resources is a task that may be performed effectively without previous training. Sex-specific and age-specific differences in the net energy expenditure of digging were detected, even though both sexes exhibited similar proficiency levels when performing the task. Our results highlight that both boys and girls spend considerable energy while digging, with differences largely driven by body size and age. Other factors beyond ability and experience, such as strength and body size, may influence the proficiency of juveniles in performing certain physically intensive foraging tasks, such as gathering tubers.
 
Three measures of humanness: (a) Ascent of Man, (b) the Face Continuum, and (c) the Human Silhouette. Ratings on each measure were coded using a 4-point scale from 1 = fully human to 4 = the least human-like (as illustrated in panel d)
Perceived humanness of the ingroup and the outgroup across three measures in adults (Study 1). (a) Ratings on the Ascent of Man scale. (b) Ratings on the Face Continuum scale. (c) Ratings on the Human Silhouette scale. To depict the levels of dehumanization, the ratings were coded using a 4-point scale from 1 = fully human to 4 = the least human-like. As such, higher ratings represent lower perceived humanness. Each histogram indicates the number of participants who made the rating
Dehumanization on each measure of humanness in adults (Study 1). Dehumanization occurs when the outgroup is more likely (odds ratio > 1) than the ingroup to be rated less human-like. Error bars represent 95% confidence intervals. Odds ratios and confidence intervals are calculated from the results reported in Table S3 in the ESM
Perceived humanness by children (Study 2) of the ingroup and the outgroup across three measures. (a) Ratings on the Ascent of Man scale. (b) Ratings on the Face Continuum scale. (c) Ratings on the Human Silhouette scale. The ratings were coded using a 4-point scale from 1 = fully human to 4 = the least human-like. As such, higher ratings represent lower perceived humanness. Each histogram indicates the number of participants who made the rating
Dehumanization on each measure of humanness in children (Study 2). Dehumanization occurs when the outgroup is more likely (odds ratio > 1 on the horizontal axis) than the ingroup to be rated less human-like. Error bars represent 95% confidence intervals. Odds ratios and confidence intervals are calculated from the results reported in ESM Table S13
Dehumanization is observed in adults across cultures and is thought to motivate human violence. The age of its first expression remains largely untested. This research demonstrates that diverse representations of humanness, including a novel one, readily elicit blatant dehumanization in adults (N = 482) and children (aged 5–12; N = 150). Dehumanizing responses in both age groups are associated with support for outgroup inferiority. Similar to the link previously observed in adults, dehumanization by children is associated with a willingness to punish outgroup transgressors. These findings suggest that exposure to cultural norms throughout adolescence and adulthood are not required for the development of outgroup dehumanization.
 
The present study examined women’s mate competition tactics in response to female and feminine-male rivals in two cultures in which competition against both occurs. In Samoa and the Istmo Zapotec (Southern Mexico), women not only compete with other women (intrasexually) but also compete with rival feminine males (intersexually) in order to access/retain the same masculine men as sexual/romantic partners. Using a mixed-method paradigm, women were asked about their experiences of intra- and intersexual mate competition, and these narratives were recorded. The tactics reportedly employed by participants, and those attributed to mate competitors, were categorized according to established taxonomies of mate competition tactics, and their frequencies compared. Within-culture, the likelihood that participant women had ever experienced intra- and intersexual mate competition did not differ. Furthermore, participants reported a similar pattern of behavioral tactics whether their rival was another woman or a feminine male. These included benefit provisioning tactics during mate acquisition and cost-inflicting tactics during mate retention. Similarly, the mate competition tactics attributed to rival women and rival feminine males bore a striking resemblance, focused on enticing target men. Results highlight the mate competition tactics employed by women outside of a Euro-American context, and the way cultural factors impact mating landscapes presumed to be exclusively heterosexual. The presence of feminine males, alongside masculine men’s willingness to engage in sexual activity with them, induces women in such cultures to compete intersexually in comparable ways to intrasexual competition with rival women.
 
Global distribution of norms of female premarital sex in the sample (N = 128)
a Decline in covariance in FPS norms with increasing phylogenetic distance among societies based on the predictors & phylogeny model. Vertical axis indicates covariance, horizontal axis indicates scaled phylogenetic distance. Gray curves show 100 draws from the joint posterior distribution of the parameters η² and ρ². Black curve shows mean covariance. b Posterior distributions of regression coefficients from the predictors model. Estimates are on the log-cumulative odds scale. Values on the right side of each distribution indicate the percentage of posterior probability (PP) that is on the expected side of zero (dashed vertical line). Color scales correspond to a given theory about FPS restrictions: purple – male control, yellow – female control, brown – parental control, and turquoise – marriage transactions/parental control
Posterior predictions based on the predictors model. Slopes indicate predicted change in the cumulative probability of each response category (vertical axis) along values of each predictor (horizontal axis) and shaded areas indicate 89% compatibility intervals. Color scales correspond to a given theory about FPS restrictions: purple – male control, yellow – female control, brown – parental control, and turquoise – marriage transactions/parental control
Although norms of premarital sex vary cross-culturally, the sexuality of adolescent girls has been consistently more restricted than that of adolescent boys. Three major theories that attempt to explain restrictions on female premarital sex (FPS) concern male, female, and parental control. These competing theories have not been tested against each other cross-culturally. In this study, we do this using a sample of 128 nonindustrial societies and socioecological predictors capturing extramarital sex, paternal care, female status, sex ratio, parental control over a daughter’s mate choice, residence, and marriage transactions, while also controlling for phylogenetic non-independence across societies. We found that multiple parties benefit from restrictions on FPS. Specifically, FPS is more restricted in societies intolerant of extramarital sex and where men transfer property to their children (male control), as well as where marriages are arranged by parents (parental control). Both paternity uncertainty (partitioned among marital fidelity and paternal investment) and parent–offspring conflict (prompting parents to control their daughter’s sexuality) were identified as possible mechanisms of FPS restrictions. The evidence for female control is ambiguous, mainly because it can be equally well interpreted as both male control and parental control, and because fathers, rather than mothers, are often the primary decision makers about a daughter’s mate choice. Our results also emphasize the importance of social roles, rather than stereotyped sex roles, as a more useful approach to understanding the evolution of FPS restrictions.
 
Proportion of information transmitted for the three content biases in the transmission chain setup of experiment 1 (Left: Negative content. Centre: Disgust-eliciting content; Right: Threat-related content). Points indicate the means, and error bars indicate standard errors
Proportion of shares for the two conditions of experiment 2, for the three content biases (Left: “anonymous sharing” condition; Right: “sharing with friends” condition)
Cultural evolution researchers use transmission chain experiments to investigate which content is more likely to survive when transmitted from one individual to another. These experiments resemble oral storytelling, wherein individuals need to understand, memorize, and reproduce the content. However, prominent contemporary forms of cultural transmission—think an online sharing—only involve the willingness to transmit the content. Here I present two fully preregistered online experiments that explicitly investigated the differences between these two modalities of transmission. The first experiment ( N = 1,080 participants) examined whether negative content, information eliciting disgust, and threat-related information were better transmitted than their neutral counterpart in a traditional transmission chain setup. The second experiment ( N = 1,200 participants) used the same material, but participants were asked whether or not they would share the content in two conditions: in a large anonymous social network or with their friends, in their favorite social network. Negative content was both better transmitted in transmission chain experiments and shared more than its neutral counterpart. Threat-related information was successful in transmission chain experiments but not when sharing, and finally, information eliciting disgust was not advantaged in either. Overall, the results present a composite picture, suggesting that the interactions between the specific content and the medium of transmission are important and, possibly, that content biases are stronger when memorization and reproduction are involved in the transmission—as in oral transmission—than when they are not—as in online sharing. Negative content seems to be reliably favored in both modalities of transmission.
 
Relationship between socioeconomic position (SEP) and average interbirth interval (IBI), grouped by ethnic self-identification, geographical region, and urban-rural living. There is a line and a point shape for each geographical region. The columns show the relationship in urban (left) and rural (right) settlements. The rows show the relationship among individuals that self-identify (or not) as Indigenous
Relationship between socioeconomic position (SEP) and birthing density, grouped by ethnic self-identification, geographical region and urban-rural living. There is a line and a point shape for each geographical region. The columns show the relationship in urban (left) and rural (right) settlements. The rows show the relationship among individuals that self-identify (or not) as Indigenous
Relationship between socioeconomic position (SEP) and age at first reproduction (AFR), grouped by geographical region. Each geographical region is indicated by a distinctive point and line color
Relationship between socioeconomic position (SEP) and age at last reproduction (ALR)
Relationship between socioeconomic position (SEP) and number of offspring, grouped by geographical region. There is a line and a point shape for each geographical region. The socioeconomic position (SEP) is square-root transformed
Globally, mortality and fertility rates generally fall as resource abundance increases.This pattern represents an evolutionary paradox insofar as resource-rich ecological contexts can support higher numbers of offspring, a component of biological fitness. This paradox has not been resolved, in part because the relationships between fertility, life history strategies, reproductive behavior, and socioeconomic conditions are complex and cultural-historically contingent. We aim to understand how we might make sense of this paradox in the specific context of late-twentieth-century, mid–demographic transition Chile. We use distribution-specific generalized linear models to analyze associations between fertility-related life-history traits—number of offspring, ages at first and last reproduction, average interbirth interval, and aver-age number of live births per reproductive span year—and socioeconomic position(SEP) using data from a cohort of 6,802 Chilean women born between 1961 and1970. We show that Chilean women of higher SEP have shorter average interbirth intervals, more births per reproductive span year, later age at first reproduction, earlier ages at last reproduction, and, ultimately, fewer children than women of lower SEP. Chilean women of higher SEP consolidate childbearing over a relatively short time span in the middle of their reproductive careers, whereas women of lower SEP tend to reproduce over the entirety of their reproductive lifespans. These patterns may indicate that different SEP groups follow different pathways toward declining fertility during the demographic transition, reflecting different life-history trade-offs in the process.
 
The predicted impact of resource-acquisition ability on the number of indicators of interest (IOI) a dating profile received. Predictions are separated by country and by sex. Ribbons showing 95% confidence intervals are present but imperceivable
The predicted impact of resource-acquisition ability on the number of indicators of interest (IOI) a dating profile received, separated by sex. Ribbons showing 95% confidence intervals are present but imperceivable
The predicted difference between high (+1 SD) vs. low (−1 SD) resource-acquisition ability on the level of interest a dating profile receives depending on the Gross National Income (GNI), Operational sex ratio (OSR), Gender Development (GDI), and proportion of the population not in education, employment, or training (NEET) of the country the profile sits in. Men and women are plotted separately for NEET due to the involvement of sex in the interaction. Lines are accompanied by ribbons showing 95% confidence intervals
How humans choose their mates is a central feature of adult life and an area of considerable disagreement among relationship researchers. However, few studies have examined mate choice (instead of mate preferences) around the world, and fewer still have considered data from online dating services. Using data from more than 1.8 million online daters from 24 countries, we examined the role of sex and resource-acquisition ability (as indicated by level of education and income) in mate choice using multilevel modeling. We then attempted to understand country-level variance by examining factors such as gender equality and the operational sex ratio. In every nation, a person’s resource-acquisition ability was positively associated with the amount of attention they received from other site members. There was a marked sex difference in this effect; resource-acquisition ability improved the attention received by men almost 2.5 times that of women. This sex difference was in every country, admittedly with some variance between nations. Several country-level traits moderated the effects of resource-acquisition ability, and in the case of unemployment this moderating role differed by sex. Overall, country-level effects were more consistent with evolutionary explanations than sociocultural ones. The results suggest a robust effect of resource-acquisition ability on real-life mate choice that transcends international boundaries and is reliably stronger for men than women. Cross-cultural variance in the role of resource-acquisition ability appears sensitive to local competition and gender equality at the country level.
 
Network digraphs of the floor sponsorship networks observed annually between 2005 and 2008. Nodes (individuals) are colored by their party (Democrats blue; Republicans red) and shaped by their gender (Males as circles; Females as squares). Reciprocal ties are black, and nonreciprocal ties are gray. Isolates (n2005 = 8, n2006 = 5, n2007 = 4, n2008 = 1) have been removed for visualization purposes
Utah state legislators organized by party and gender between 2005 and 2008. Each square represents one legislator. Values within squares denote total count of legislators with the same party and gender as square color
Bill introduction and floor sponsorship rates grouped by party, gender, or chamber between 2005 and 2008. Each observation represents the average number of bills a specific legislator introduced or floor sponsored in a year. n=133
Forest plot of parameter estimates (β^\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\widehat{\mathrm{\beta}}$$\end{document}) and confidence intervals (CI) from our full Stochastic Actor-Oriented Model. Note that our outdegree and ego parameters depict authors to successfully recruit floor sponsors, while indegree and alter denote the tendency for legislators to be successfully recruited as floor sponsors. Similarity means the tendency for floor sponsorship to occur between legislators who score similarly on that covariate. See text for further explanation and interpretation of our parameters
Social network analysis has become an increasingly important tool among political scientists for understanding legislative cooperation in modern, democratic nation-states. Recent research has demonstrated the influence that group affinity (homophily) and mutual exchanges (reciprocity) have in structuring political relationships. However, this literature has typically focused on political cooperation where costs are low, relationships are not exclusive, and/or partisan competition is high. Patterns of legislative behavior in alternative contexts are less clear and remain largely unexamined. Here, we compare theoretical expectations of cooperation in these contexts from the political and biosocial sciences and implement the first assessment of political alliance formation in a novel legislative environment where costs to cooperation are high and party salience low. We implement a stochastic actor-oriented model (SAOM) to examine bill floor sponsorship, a process in which a “floor sponsor” becomes the exclusive advocate for a colleague’s piece of legislation, in the Utah state legislature from 2005 to 2008—a context in which gender (male) and political party (Republican) supermajorities exist. We find that (1) party and gender homophily predict who legislators recruit as floor sponsors, whereas seniority does not, and (2) legislators frequently engage in reciprocal exchanges of floor sponsorship. In addition, whereas gender homophily increases the likelihood of reciprocity, party homophily decreases it. Our findings suggest that when the cost of cooperation is high, political actors use in-group characteristics for initiating alliances, but once a cooperative relationship is established with an out-group political member, it is reinforced through repeated exchanges. These findings may be useful for understanding the rise of political polarization and gridlock in democracies internationally.
 
Forming long-term intimate relationships constitutes an important aspect of human nature. Within the context of an evolutionary theoretical framework, the current research has attempted to investigate what motivates people to keep an intimate relationship. Using a combination of qualitative research methods in a sample of 131 Greek-speaking participants, 58 reasons that motivated individuals to keep their intimate relationship were identified. Using quantitative research methods in a sample of 789 Greek-speaking participants who were in an intimate relationship, these reasons were classified in nine broad factors and two broader domains. Having a supporting and compatible partner with whom one shares similar goals, and with whom one has good sex and a strong emotional attachment, were rated among the most important factors motivating participants to keep their relationship. Moreover, as indicated by the domain means, participants were more strongly motivated to keep their intimate relationship if their partners had desirable attributes, such as providing them with support, and less so by their own attributes, such as fear of loneliness. Significant effects of sex, age, marital status, presence of children, and years in a relationship were found for several factors.
 
Research in various disciplines has highlighted that humans are uniquely able to solve the problem of cooperation through the informal mechanisms of reputation and gossip. Reputation coordinates the evaluative judgments of individuals about one another. Direct observation of actions and communication are the essential routes that are used to establish and update reputations. In large groups, where opportunities for direct observation are limited, gossip becomes an important channel to share individual perceptions and evaluations of others that can be used to condition cooperative action. Although reputation and gossip might consequently support large-scale human cooperation, four puzzles need to be resolved to understand the operation of reputation-based mechanisms. First, we need empirical evidence of the processes and content that form reputations and how this may vary cross-culturally. Second, we lack an understanding of how reputation is determined from the muddle of imperfect, biased inputs people receive. Third, coordination between individuals is only possible if reputation sharing and signaling is to a large extent reliable and valid. Communication, however, is not necessarily honest and reliable, so theoretical and empirical work is needed to understand how gossip and reputation can effectively promote cooperation despite the circulation of dishonest gossip. Fourth, reputation is not constructed in a social vacuum; hence we need a better understanding of the way in which the structure of interactions affects the efficiency of gossip for establishing reputations and fostering cooperation.
 
Core audiovisual sequence presented to participants for this experiment on the computer screen. Screen 1: Five seconds after the instruction at the top of the screen appeared, an icon emerged from the middle-left side of the screen with a “Boy A” or “Girl A” indicated below, and then a neutral sentence (e.g., uttered by a 5-year-old child) was presented. Screen 2: One second later the second icon with a “Boy B” or “Girl B” indicated below appeared, and the same neutral sentence uttered by the other child of the pair (in this example, a 10-year-old child) was presented. Screen 3: After the participant pressed a key on the keyboard, the first question appeared at the bottom of the screen; once the first question was answered, 13 more questions with their corresponding 13 adjectives or short statements were delivered sequentially, in random order, at the same screen place
Proportion of people selecting the child with the immature voice (Voices-Only), the immature supernatural thinking (Vignettes-Only), and the immature face (Faces-Only) by trait dimension (Positive Affect, Negative Affect, Intelligence, Helpless). Voices-Only data is from the current study; Vignettes-Only and Faces-Only data from Hernández Blasi et al. (2015) for comparative purposes. Note: t tests on scores between .40 and .60 were not statistically different from chance in their corresponding studies; scores above .60 reflect that immature children were selected significantly greater than expected by chance; and scores below .40 indicate that mature children were selected significantly greater than expected by chance
Mean pitch (fundamental frequency, in Hz) for a sample of 42 4- to 11-year-old children (22 boys, 20 girls) when verbalizing a neutral-content sentence (“I like the beach more than the mountains”)
The aim of this study was to explore the role of voices as cues to adults of children’s needs for potential caregiving during early childhood. To this purpose, 74 college students listened to pairs of 5-year-old versus 10-year-old children verbalizing neutral-content sentences and indicated which voice was better associated with each of 14 traits, potentially meaningful in interactions between young children and adults. Results indicated that children with immature voices were perceived more positively and as being more helpless than children with mature voices. Children’s voices, regardless of the content of speech, seem to be a powerful source of information about children’s need for caregiving for parents and others during the first six years of life.
 
Nine levels in the explanation of behavior
Reciprocal causation in the nine-level model
Tinbergen’s classic “On Aims and Methods of Ethology” (Zeitschrift für Tierpsychologie, 20, 1963) proposed four levels of explanation of behavior, which he thought would soon apply to humans. This paper discusses the need for multilevel explanation; Huxley and Mayr’s prior models, and others that followed; Tinbergen’s differences with Lorenz on “the innate”; and Mayr’s ultimate/proximate distinction. It synthesizes these approaches with nine levels of explanation in three categories: phylogeny, natural selection, and genomics (ultimate causes); maturation, sensitive period effects, and routine environmental effects (intermediate causes); and hormonal/metabolic processes, neural circuitry, and eliciting stimuli (proximate causes), as a respectful extension of Tinbergen’s levels. The proposed classification supports and builds on Tinbergen’s multilevel model and Mayr’s ultimate/proximate continuum, adding intermediate causes in accord with Tinbergen’s emphasis on ontogeny. It requires no modification of Standard Evolutionary Theory or The Modern Synthesis, but shows that much that critics claim was missing was in fact part of Neo-Darwinian theory (so named by J. Mark Baldwin in The American Naturalist in 1896) all along, notably reciprocal causation in ontogeny, niche construction, cultural evolution, and multilevel selection. Updates of classical examples in ethology are offered at each of the nine levels, including the neuroethological and genomic findings Tinbergen foresaw. Finally, human examples are supplied at each level, fulfilling his hope of human applications as part of the biology of behavior. This broad ethological framework empowers us to explain human behavior—eventually completely—and vindicates the idea of human nature, and of humans as a part of nature.
 
Map of the study area in Norway. Kautokeino is in Troms and Finnmark County (marked with light blue) in the North. Røros is in Sør-Trøndelag and Hedmark County (marked with light blue) in the South. Reindeer districts are marked with orange, red, and blue. Map created in Python 3.8.10 (https:// www. python. org/) with background map from GADM (https:// gadm. org/ maps/ NOR. html and official reindeer districts from the Norwegian Institute of Bioeconomy Research's Kilden (https:// kart8. nibio. no/ nedla sting/ dashb oard)
Map of the study area in Norway. Kautokeino is in Troms and Finnmark County (marked with light blue) in the North. Røros is in Sør-Trøndelag and Hedmark County (marked with light blue) in the South. Reindeer districts are marked with orange, red, and blue. Map created in Python 3.8.10 (https://www.python.org/) with background map from GADM (https://gadm.org/maps/NOR.html and official reindeer districts from the Norwegian Institute of Bioeconomy Research’s Kilden (https://kart8.nibio.no/nedlasting/dashboard)
Contour plot showing the size of gifts given in the South (A) and North (B) as a function of the effect of the cooperative context (CoopAround) and kinship (r). Points show the scatterplot of CoopAround as a function of r, whereas contour lines show the predicted values from the model presented in Table 3. Please note that the predicted values are were back-transformed from loge- to normal-scale based on the model output presented in Table 3. See ESM §4 for a visualization of how the two predictor variables affect the effect sizes (the estimated slope, or β) of each other
Contour plot showing the size of gifts received in the South (A) and North (B) as a function of the effect of the cooperative context (CoopAround) and kinship (r) from the model presented in Table 4. The caption for Fig. 2 provides technical details
Descriptive statistics of the participants in the different regions
Kin relations have a strong theoretical and empirical basis for explaining cooperative behavior. Nevertheless, there is growing recognition that context—the cooperative environment of an individual—also shapes the willingness of individuals to cooperate. For nomadic pastoralists in Norway, cooperation among both kin and non-kin is an essential predictor for success. The northern parts of the country are characterized by a history of herder-herder competition exacerbating between-herder conflict, lack of trust, and subsequent coordination problems. In contrast, because of a history of herder-farmer competition, southern Norway is characterized by high levels of between-herder coordination and trust. This comparative study investigates the relative importance of “cooperative context” and kinship in structuring cooperative behavior using an experimental gift game. The main findings from this study were that in the South, a high level of cooperation around an individual pushes gifts to be distributed evenly among other herders. Nevertheless, kinship matters, since close kin give and receive larger gifts. In contrast, kinship seems to be the main factor affecting gift distribution in the North. Herders in the North are also concerned with distributing gifts equally, albeit limiting them to close kin: the level of intragroup cooperation drives gifts to be distributed evenly among other closely related herders. The observed regional contrasts in cooperative decisions fit with the different historical levels of conflict and trust in the two regions: whereas herders in the South are affected by both cooperative context and kinship, kinship seems to be the main determinant of cooperation in the North.
 
Percentage of different disguise tactics used across the hunter-gatherer societies in the PSF. N = 24 total disguise cases. Animal mimicry, impersonate spirits, and masquerade as plants involved an actor or actors disguising themselves as an animal species, a “spirit-being,” or as plant species respectively. Disruptive coloration involved the use of pigment or other materials to create false edges to hinder recognition of parts of an actor’s true outline and shape, while background matching involved the use of clothing to blend into the color of a background
Percentage of cases where each material was used as part of disguises. N = 24 total disguise cases, with some cases including multiple materials (see ESM Table S1)
Different clothing types/motives for clothing use among the hunter-gatherer societies in the PSF
Hunter-gatherer societies in the Probability Sample Files (PSF) with reported contexts of disguise use
Strategies and context of disguise use across the hunter-gatherer societies in the PSF
Thermoregulation is often thought to be a key motivating factor behind the origins of clothing. Less attention has been given, however, to the production and use of clothing across traditional societies in contexts outside of thermoregulatory needs. Here I investigate the use of disguises, modesty coverings, and body armor among the 10 hunter-gatherer societies in the Probability Sample Files (PSF) within the Human Relations Area Files (HRAF) World Cultures database, with a particular focus on disguise cases and how they compare with strategies of deception across other taxa. The employment of disguises-defined as altering one's appearance for purposes of deceiving conspecifics or other animals-is noted for eight of the 10 societies, with their use occurring in contexts of hunting, religious or cult practices, and war or interpersonal violence. Most hunter-gatherer disguises demonstrated clear similarities to cases of visual deception found in other species, with the majority of examples fitting categories of animal mimicry, masquerading as plants, disrup-tive coloration (camouflage), or background matching (camouflage), while disguises unique to humans involved the impersonation of culture-specific "spirit-beings." Clothing for modesty purposes (nine societies) and body armor (six societies) are also noted. I propose that strategic initiatives by individuals or groups to disguise or conceal themselves represents one possible initial pathway to the cultural evolution of clothing. There are likely multiple potential (nonexclusive) social and functional pathways to the emergence of clothing outside of thermoregulatory needs.
 
Research has found that both cisgender and transgender androphilic males (i.e., males sexually attracted to and aroused by other adult males) have female-typical occupational preferences when compared with gynephilic males (i.e., males sexually attracted to and aroused by adult females). Moreover, whereas cisgender androphilic males’ occupational preferences tend to be intermediate between those of gynephilic men and androphilic women, transgender androphilic males tend to have occupational preferences that are more similar to androphilic women. No study has directly compared both types of androphilic males within the same culture. The present study investigated occupational preference and its relation to childhood sex-atypical behavior (CSAB), among gynephilic men (n = 208), androphilic women (n = 138), and cisgender (n = 132) and transgender (n = 129) androphilic males from the Istmo region of Oaxaca, Mexico, where androphilic males are recognized as third gender, muxes. The study found large sex differences in occupational preferences (d = 2.80). Furthermore, both cisgender muxe nguiiu (d = 2.36) and transgender muxe gunaa (d = 3.44) reported having more sex-atypical occupational preferences compared with men. However, muxe gunaa reported higher female-typical occupational preferences than women (d = 0.59) and muxe nguiiu (d = 0.57), whereas muxe nguiiu and women did not differ (d = 0.08). These findings are consistent with the conclusion that sex-atypical occupational preferences are a cross-culturally universal aspect of male androphilia. Finally, CSAB was associated with sex-atypical occupational preferences among all participants. These findings suggest that a developmental continuity exists between childhood and adulthood sex-atypicality.
 
Volunteers simulating the gestures and movements involved in the outdoor multitask activity (Gymkhana). a Walking trial. b–d Locomotion and picking gestures used during the Gathering trial
Effect of body mass on GrossCOT in both tests a, b. The dotted line represents the trend for both sexes together. Red thin and blue thick lines show the trends for girls and boys, respectively. The regression equations are shown in Tables 2 and 3
In some small-scale societies, a sexual division of labor is common. For subadult hunter-gatherers, the onset of this division dates to middle childhood and the start of puberty; however, there is apparently no physiological explanation for this timing. The present study uses an experimental approach to evaluate possible energetic differences by sex in gathering-related activities. The energetic cost of gathering-related activities was measured in a sample of 42 subjects of both sexes aged between 8 and 14 years. Body mass and other anthropometric variables were also recorded. Our results show that the energetic differences in the simulated gathering activities depend only on body mass. Both sexes expend a similar amount of energy during locomotion activities related to gathering. Discarding the energetic factor, the sexual division of tasks may be explained as an adaptation to acquire the skills needed to undertake the complex activities required during adulthood as early as possible. Carrying out gathering activities during childhood and adolescence could be favored by the growth and development cycles of Homo sapiens. Moreover, if most of the energetic costs of gathering activities depend on body mass, the delayed growth in humans relative to other primates allows subadults to practice these tasks for longer periods, and to become better at performing them. In fact, this strategy could enable them to acquire adults’ complex skills at a low energetic cost that can be easily subsidized by other members of the group.
 
Map of the study region, with place names mentioned in the text
Judges, alters, and experimenters in experiments 1–3. Photo by Bram Tucker
Distribution of classification success rate in experiments 1–3, by ethnicity of judges and alters
Random and fixed effects, experiments 1–3
Results of experiment 4. (a) Fixed and random effects. (b) Test of probabilities that judges of one sex were more likely to trust or mistrust alters of the same or different sex
People often signal their membership in groups through their clothes, hairstyle, posture, and dialect. Most existing evolutionary models argue that markers label group members so individuals can preferentially interact with those in their group. Here we ask why people mark ethnic differences when interethnic interaction is routine, necessary, and peaceful. We asked research participants from three ethnic groups in southwestern Madagascar to sort photos of unfamiliar people by ethnicity, and by with whom they would prefer or not prefer to cooperate, in a wage labor vignette. Results indicate that southwestern Malagasy reliably send and detect ethnic signals; they signal less in the marketplace, a primary site of interethnic coordination and cooperation; and they do not prefer co-ethnics as cooperation partners in novel circumstances. Results from a cultural knowledge survey and calculations of cultural FST suggest that these ethnic groups have relatively little cultural differentiation. We concur with Moya and Boyd (Human Nature 26:1–27, 2015) that ethnicity is unlikely to be a singular social phenomenon. The current functions of ethnic divisions and marking may be different from those at the moment of ethnogenesis. Group identities may persist without group conflict or differentiation.
 
Signs such as this one are found at all entrances to the MSC, instructing patrons to remove their hats and explaining the motivation to do so
Responses to the question “Assuming that you have asked them to uncover, they declined and moved on, what would you do next? (Check all that apply, assuming that the person continues to decline each request)”
Hat behavior, norm compliance and punishment at the MSC. (a) shows the frequency of hat wearing. (b) shows norm compliance among those who wear hats. (c) shows the frequency of enforcement on a subsample of hat wearers
Hat removal at the three sites. Hat-wearers entering the MSC are significantly more likely to remove their hats than those entering Evans Library or HEB
Hazard of punishment. Punishment varied with protocol but was not consistent with the expectation that violators would be vigorously reprimanded
Culturally inherited institutional norms structure much of human social life. Successfully replicating institutions train their current members to behave in the generally adaptive ways that served past members. Ancestor veneration is a well-known manifestation of this phenomenon whereby deference is conferred to prestigious past members who are used as cultural models. Such norms of respect may be maintained by punishment based on evidence from theory and laboratory experiments, but there is little observational evidence to show that punishment is commonly used. To test for punishment as a mechanism that maintains these norms, we examine a norm of ancestor veneration in a natural field experiment at the Memorial Student Center (MSC) at Texas A&M University. The MSC is a memorial to university war dead, and the expectation is that all who enter the building remove their hats out of respect. Observations reveal that hat removal is significantly more common at the MSC than at two control locations. Survey data indicate that most, but not all, subjects understand the norm to be veneration of the dead, and most expect others to follow the norm. Many report a strong negative emotional response when asked to imagine the norm being violated. Sixty-two percent report they would definitely or probably ask the noncompliant to uncover. Focal follow data show that punishment is relatively rare, however, with the majority of behatted subjects going unreproached as they pass through the building. Both survey and observational data indicate there is a motivated minority that enthusiastically enforces the norm.
 
Religions “in the wild” are the varied set of religious activities that occurred before the emergence of organized religions with doctrines, or that persist at the margins of those organized traditions. These religious activities mostly focus on misfortune; on how to remedy specific cases of illness, accidents, failures; and on how to prevent them. I present a general model to account for the cross-cultural recurrence of these particular themes. The model is based on (independently established) features of human psychology—namely, (a) epistemic vigilance, the set of systems whereby we evaluate the quality of information and of sources of information, and (b) threat-detection psychology, the set of evolved systems geared at detecting potential danger in the environment. Given these two sets of systems, the dynamics of communication will favor particular types of messages about misfortune. This makes it possible to predict recurrent features of religious systems, such as the focus on nonphysical agents, the focus on particular cases rather than general aspects of misfortune, and the emergence of specialists. The model could illuminate not just why such representations are culturally successful, but also why people are motivated to formulate them in the first place.
 
Although a substantial literature in anthropology and comparative religion explores divination across diverse societies and back into history, little research has integrated the older ethnographic and historical work with recent insights on human learning, cultural transmission, and cognitive science. Here we present evidence showing that divination practices are often best viewed as an epistemic technology, and we formally model the scenarios under which individuals may overestimate the efficacy of divination that contribute to its cultural omnipresence and historical persistence. We found that strong prior belief, underreporting of negative evidence, and misinferring belief from behavior can all contribute to biased and inaccurate beliefs about the effectiveness of epistemic technologies. We finally suggest how scientific epistemology, as it emerged in Western societies over the past few centuries, has influenced the importance and cultural centrality of divination practices.
 
Friendship network. These social network data consist of connections among the men (blue circles) and women (orange circles) of the collegiate athletic team and the number of Friendships on the team. The image has a dense amount of both one-directional arrows, which indicates a large number of connections and a very closely-knit team
Positive gossip network. These social network data consist of connections among the men (blue circles) and women (orange circles) of the collegiate athletic team and the amount of Positive Gossip. The dense amount of connections indicates that there is a large amount of Positive Gossip on the team
Negative gossip network. These social network data consist of connections among the men (blue circles) and women (orange circles) of the collegiate athletic team and the amount of Negative Gossip. The dense amount of connections indicates that there is Negative Gossip on the team
Gossip (evaluative talk about others) is ubiquitous. Gossip allows important rules to be clarified and reinforced, and it allows individuals to keep track of their social networks while strengthening their bonds to the group. The purpose of this study is to decipher the nature of gossip and how it relates to friendship connections. To measure how gossip relates to friendship, participants from men’s and women’s collegiate competitive rowing (crew) teams (N = 44) noted their friendship connections and their tendencies to gossip about each of their teammates. Using social network analysis, we found that the crew members’ friend group connectedness significantly correlated with their positive and negative gossip network involvement. Higher connectedness among friends was associated with less involvement in spreading negative gossip and/or being a target of negative gossip. More central connectedness to the friend group was associated with more involvement in spreading positive gossip and/or being a target of positive gossip. These results suggest that the spread of both positive and negative gossip may influence and be influenced by friendship connections in a social network.
 
Frequencies of general namesakes (a, d), paternal namesakes (b, e), and maternal namesakes (c, f) across sex (top row) and primogeniture (bottom row). Asterisks indicate significant differences at * < 0.05, ** < 0.01, *** < 0.001; "ns" is nonsignificant. P-values are based on the χ 2 test (see "Results")
Coefficient plots for the regression models. From the top left, LMM/GLMM for the s-EMBU: a protection, b rejection, and c emotional warmth. From the bottom left, CLMM: d relationship quality, e financial investment, and f time investment. Estimates for the s-EMBU models are in units of predictors. Estimates for the relationship quality, financial investment and time investment models are on the logit scale. Error bars represent 95% CI. Predictor has a significant effect when its confidence intervals (CI) do not include zero (vertical dashed line)
Namesaking (naming a child after a parent or other relative) can be viewed as a mechanism to increase perceived parent-child similarity and, consequently, parental investment. Male and, to a lesser extent, firstborn children are more frequently namesakes than female and later-born children, respectively. However, a direct link between namesaking and parental investment has not been examined. In the present study, 632 participants (98 men and 534 women) from Central Europe indicated their first name, sex, birth order, number of siblings, sexual orientation, socioeconomic status, paternal and maternal first names, as well as relationship quality with, and time and financial investment they received from, both parents during childhood. Mixed-effects models revealed associations between namesaking and parental investment. However, the effect of namesaking often appeared significant only in interaction with specific predictors, such as sex and primogeniture. It suggests instead that namesaking has an additive effect-it enhances the effect of biological factors on parental investment. In general, we found evidence for the bias in parental investment linked to name similarity among both parents, and support for the hypothesis that namesaking serves as a mechanism to increase paternity confidence and, thus, paternal investment. The effect of namesaking influences only certain types of parental investment-namely, those at the level of relationship quality. In addition, nonheterosexual orientation was the strongest negative predictor of paternal investment. Our study extends the research on parental investment by showing that cultural mechanisms, such as namesaking, can also exert some influence on parental rearing behavior.
 
Exclusive breastfeeding (EBF)—giving infants only breast-milk for the first 6 months of life—is a component of optimal breastfeeding practices effective in preventing child morbidity and mortality. EBF practices are known to vary by population and comparable subnational estimates of prevalence and progress across low- and middle-income countries (LMICs) are required for planning policy and interventions. Here we present a geospatial analysis of EBF prevalence estimates from 2000 to 2018 across 94 LMICs mapped to policy-relevant administrative units (for example, districts), quantify subnational inequalities and their changes over time, and estimate probabilities of meeting the World Health Organization’s Global Nutrition Target (WHO GNT) of ≥70% EBF prevalence by 2030. While six LMICs are projected to meet the WHO GNT of ≥70% EBF prevalence at a national scale, only three are predicted to meet the target in all their district-level units by 2030
 
Screenshots from the experimental video showing the control condition (top: babies moving their mouths) and the yawning condition (bottom)
Effect of the type of the video condition (yawning/control) on the yawning response (experimental setting). Line plot showing the yawning response (Y axis) in the experimental setting as a function of the condition (yawning/control; X axis). The presence of a yawning response was significantly more likely in the yawning (M = 0.3322; SE = 0.039) than in the control (M = 0.120; SE = 0.026) condition (statistical results: Table 1), which confirms the presence of yawn contagion. Mean (circle) and 95% confidence interval (bars) are indicated
Effect of the reproductive status on the yawning response (experimental setting). Line plot showing the yawning response (Y axis) in the experimental setting as a function of the reproductive status of the woman potential responder (nulliparous/pregnant; X axis). The presence of a yawning response in the yawning video condition was significantly more likely (M = 0.416; SE = 0.057) in pregnant than in nulliparous (M = 0.217; SE = 0.050) women (Statistical results: Table 2). Mean (circle) and 95% confidence interval (bars) are indicated
Effect of the social bond on the yawning response (naturalistic setting). Line plot showing the yawning response (Y axis) in the naturalistic setting as a function of social bond between trigger and potential responder (strangers/acquaintances; X axis). The presence of a yawning response was significantly more likely between acquaintances (Mean ± SE: 0.168 ± 0.031) than between strangers (M = 0.164; SE = 0.029) (statistical results: Table 3). Mean (circle) and 95% confidence interval (bars) are indicated
Effect of the reproductive status on the yawning response (naturalistic setting). Line plot showing the yawning response (Y axis) in the naturalistic setting as a function of the reproductive status of the woman potential responder (nulliparous/pregnant; X axis). The presence of a yawning response was significantly more likely in pregnant (M = 0.225; SE = 0.036) than in nulliparous (M = 0.118; SE = 0.025) women (statistical results: Table 3). Mean (circle) and 95% confidence interval (bars) are indicated
Contrary to spontaneous yawning, which is widespread in vertebrates and probably evolutionary ancient, contagious yawning—yawning triggered by others’ yawns—is considered an evolutionarily recent phenomenon, found in species characterized by complex sociality. Whether the social asymmetry observed in the occurrence of contagious yawning is related to social and emotional attachment and may therefore reflect emotional contagion is a subject of debate. In this study we assessed whether yawn contagion was enhanced in pregnant women, a cohort of subjects who develop prenatal emotional attachment in preparation for parental care, via hormonal and neurobiological changes. We predicted that if yawn contagion underlies social and emotional attachment, pregnant women would be more likely to contagiously yawn than nonpregnant, nulliparous women of reproductive age. We gathered data in two different settings. In the experimental setting, 49 women were exposed to video stimuli of newborns either yawning or moving their mouth (control) and we video-recorded the women during repeated trials to measure their yawning response. In the naturalistic setting, 131 women were observed in a social environment and their yawning response was recorded. We tested the factors influencing the yawning response, including the reproductive status (pregnant vs. not pregnant). In both settings, yawn contagion occurred significantly more in pregnant than nonpregnant women. By showing that pregnant women were most likely to respond to others’ yawns, our results support the hypothesis that the social variation observed in yawn contagion may be influenced by emotional attachment and that yawning in highly social species might have been coopted for emotional contagion during evolution.
 
Map showing the location of the study. We conducted interviews with 24 ranchers in this region and sent out 1053 surveys to owners of registered cattle brands in Cochise and Hidalgo counties. We received 118 surveys in return from respondents who indicated they were ranchers
Proportion of respondents who expect some kind of payment in return for help provided for a particular reason or of a particular type (yellow) and proportion of respondents who reported that the need for a particular kind of help or a particular reason for help arises at times that are either very or somewhat unpredictable (blue)
Mean expectations of repayment for helping at each level of predictability of risk. Ranchers’ expectations of repayment for the help they provide increase as the predictability of the type of help or the reason why the help is needed increases
When responses of “same kind of help at a later date” are interpreted not as expressions of a repayment requirement but as an expectation that respondents will be helped if similar events should befall someone on their ranch, the proportion of respondents who expect repayment is reduced. Y axis is the proportion of responses expressing an expectation of repayment
To better understand risk management and mutual aid among American ranchers, we interviewed and mailed a survey to ranchers in Hidalgo County, New Mexico, and Cochise County, Arizona, focusing on two questions: (1) When do ranchers expect repayment for the help they provide others? (2) What determines ranchers’ degrees of involvement in networks of mutual aid, which they refer to as “neighboring”? When needs arise due to unpredictable events, such as injuries, most ranchers reported not expecting to be paid back for the help they provide. When help is provided for something that follows a known schedule or that can be scheduled, such as branding, most ranchers did expect something in return for the help they provide. This pattern makes sense in light of computational modeling that shows that transfers to those in need without expectations of repayment pool risk more effectively than transfers that create debt. Ranchers reported helping other ranchers more often when they belonged to more religious and civic organizations, when they owned larger ranches, when they relied less on ranch vs. other income, and when they had more relatives in the area. Operators of midsize ranches reported helping other ranchers more frequently than did those on smaller and larger ranches. None of our independent variables predicted how many times ranchers reported receiving help from other ranchers. Although ranch culture in the American West is often characterized by an ethic of individualism and independence, our study suggests that this ethic stands alongside an ethic of mutual aid during times of need.
 
Bar-scatter plot of testosterone reactivity to watching a teammate compete by condition (win/loss). Horizontal lines represent the respective group medians, white boxes represent the middle 50% of the data, and the vertical lines represent the data range
The relationship between cognitive centrality and T reactivity by condition (win/loss). Bars around trendlines indicate 95% confidence intervals and area slopes around exterior represent frequency distributions of the data (density plots). This figure excludes one outlier; N = 25. See https://osf.io/tu6ns/ for replica of figure that includes the outlier
Testosterone (T) fluctuates in response to competitive social interactions, with the direction of change typically depending on factors such as contest outcome. Watching a competition may be sufficient to activate T among fans and others who are invested in the outcome. This study explores the change in T associated with vicarious experiences of competition among combat sport athletes viewing a teammate win or lose and assesses how individual differences in social identification with one’s team relates to these patterns of T reactivity. Twenty-six male combat athletes completed a social identity questionnaire on a neutral day. Later, salivary samples (assayed for T) were obtained before and after athletes viewed a video of a teammate engaged in a formal contest. T reactivity to viewing a teammate compete varied among participants in both the magnitude and direction of change, independent of contest outcome. Individual differences in cognitive centrality, a core feature of social identification, showed a strong positive relationship with T reactivity, particularly if their teammate won. Initial findings suggest that dominance-linked androgen responses associated with watching a teammate win a competition might depend on the belief that team membership is central to one’s own identity. These exploratory results in a small sample of combat athletes should be interpreted with caution. Uncovering the role of social group dynamics in influencing T responses to competition is particularly important in light of the evolutionary history of coalitional combat in humans.
 
Frequencies of general namesakes (a, d), paternal namesakes (b, e), and maternal namesakes (c, f) across sex (top row) and primogeniture (bottom row). Asterisks indicate significant differences at * < 0.05, ** < 0.01, *** < 0.001; "ns" is nonsignificant. P-values are based on the χ 2 test (see "Results")
Coefficient plots for the regression models. From the top left, LMM/GLMM for the s-EMBU: a protection, b rejection, and c emotional warmth. From the bottom left, CLMM: d relationship quality, e financial investment, and f time investment. Estimates for the s-EMBU models are in units of predictors. Estimates for the relationship quality, financial investment and time investment models are on the logit scale. Error bars represent 95% CI. Predictor has a significant effect when its confidence intervals (CI) do not include zero (vertical dashed line)
Namesaking (naming a child after a parent or other relative) can be viewed as a mechanism to increase perceived parent-child similarity and, consequently, parental investment. Male and, to a lesser extent, firstborn children are more frequently namesakes than female and later-born children, respectively. However, a direct link between namesaking and parental investment has not been examined. In the present study, 632 participants (98 men and 534 women) from Central Europe indicated their first name, sex, birth order, number of siblings, sexual orientation, socioeconomic status, paternal and maternal first names, as well as relationship quality with, and time and financial investment they received from, both parents during childhood. Mixed-effects models revealed associations between namesaking and parental investment. However, the effect of namesaking often appeared significant only in interaction with specific predictors, such as sex and primogeniture. It suggests instead that namesaking has an additive effect-it enhances the effect of biological factors on parental investment. In general, we found evidence for the bias in parental investment linked to name similarity among both parents, and support for the hypothesis that namesaking serves as a mechanism to increase paternity confidence and, thus, paternal investment. The effect of namesaking influences only certain types of parental investment-namely, those at the level of relationship quality. In addition, nonheterosexual orientation was the strongest negative predictor of paternal investment. Our study extends the research on parental investment by showing that cultural mechanisms, such as namesaking, can also exert some influence on parental rearing behavior.
 
Previous research indicates that Euro-American women are more upset by imagining their male partners committing homosexual infidelities than heterosexual ones. The present studies sought to replicate these findings and extend them to two non-Western cultures wherein masculine men frequently engage in sexual interactions with feminine third-gender males. Across six studies in three cultural locales (Canada, Samoa, and the Istmo Zapotec), women were asked to rate their degree of upset when imagining that their partner committed infidelity that was heterosexual in nature, as well as infidelity that was homosexual. In two Canadian undergraduate samples, women reported greater upset at imagining partner infidelity with a female, whereas a community sample of middle-aged women reported equal upset across infidelity types. Samoan women reported substantially less upset at the thought of partner infidelity with a third-gender male (fa'afafine) than with a female. Istmo Zapotec women reported equal upset toward infidelity with a female or a third-gender male (muxe), whereas a second Zapotec sample reported slightly greater upset at the thought of infidelity with a muxe. Results illustrate how cultural contexts moderate the degree to which same-sex infidelity scenarios are upsetting to women.
 
Sex ratios have widely been recognized as an important link between demographic contexts and behavior because changes in the ratio shift sex-specific bargaining power in the partner market. Implicitly, the literature considers individual partner market experiences to be a function of local sex ratios. However, empirical evidence on the correspondence between subjective partner availability and local sex ratios is lacking so far. In this paper, we analyzed how closely a set of different local sex ratio measures correlates with subjective partner market experiences. Linking a longitudinal German survey to population data for different entities (states, counties, municipalities), we used multilevel logistic regression models to explore associations between singles’ subjective partner market experiences and various operationalizations of local sex ratios. Results suggest that local sex ratios correlated only weakly with subjective partner market experiences. Adult sex ratios based on broad age brackets, including those for lower-level entities, did not significantly predict whether individuals predominantly met individuals of their own sex. More fine-grained, age-specific sex ratios prove to be better predictors of subjective partner market experiences, in particular when age hypergamy patterns were incorporated. Nevertheless, the respective associations were only significant for selected measures. In a complementary analysis, we illustrate the validity of the subjective indicator as a predictor of relationship formation. In sum, our results suggest that subjective partner availability is not adequately represented by the broad adult sex ratio measures that are frequently used in the literature. Future research should be careful not to equate local sex ratios and conscious partner market experiences.
 
Fifteen motifs or kupesi gathered from continual scans in public spaces across Nuku’alofa, Tonga, in 2016
Recognition of motifs. Motifs along the horizontal axis were the result of a continuous scan in public spaces (Fig. 1). Bars show the fraction of the time the respondents answered “yes” to having seen a motif, and the numbers below the images report the percent of participants providing a name for a motif. Calculations stem from 70 ethnographic surveys in Tonga
Similarity of choices in the motif classification task across a Tongan and a reference population. The left panel plots the results of multidimensional scaling, performed on a difference matrix of values across all possible dyads for 114 Tongan participants and 51 U.S. non-Tongan students. Cluster analysis suggests two clusters, with the group of solid points to the right forming a separate cluster from the rest of the plot. The right panel shows dendrograms generated from the same difference matrix, showing where the differences in classification lie between the Tongan and reference sample
Ethnic markers are a prominent organizing feature of human society when individuals engage in significant anonymous interactions. However, identifying markers in natural settings is nontrivial. Although ad hoc assignment of markers to groups is widely documented in the ethnographic literature, predicting the membership of individuals based on stylistic variation is less clear. We argue that a more systematic approach is required to satisfy the basic assumptions made in ethnic marker theory. To this end we introduce a three-step ethnographic method to assess the presence, recognition, and transmission of markers of group identity: (1) continual scans, (2) a utilization survey, and (3) a comparative classification task. Applying the method to a study of culturally significant motifs in the South Pacific Island nation of Tonga, we provide evidence that the motif set satisfies basic theoretical assumptions and thus the motifs are likely expressions for social coordination. We also found that the coordinating role of each motif is variable and requires further investigation.
 
This study analyzes the influence of grandmothers’ household residency on the presence of low height-for-age and excessive fat (FMI = fat mass [kg]/height [m2]), waist circumference, and sum of triceps and subscapular skinfolds in a sample of 247 6- to 8-year-old urban Maya children from Yucatan, Mexico. Between September 2011 and January 2014, we obtained anthropometric and body composition data from children and mothers, as well as socioeconomic characteristics of participants and households. Grandmothers’ place of residence was categorized as either in the same household as their grandchildren (n = 71) or in separate households (n = 176). Multiple logistic regression models were used to analyze the association between grandmothers’ residency and outcome variables. Models were adjusted for maternal anthropometric characteristics and the following socioeconomic variables: family size, location, maternal education, monthly family income, and household crowding. Models showed that the presence of grandmothers in their grandchildren’s households was not associated with any of the outcome variables. In contrast, larger family size, overcrowding in the household, and lower family income predicted low height-for-age in children. Larger family size decreased the risk for being overweight based on the three parameters of body composition. Overcrowding in the household increased the risk for greater skinfolds thickness, while low family income increased the risk for higher fat mass index. The residency of grandmothers in their adult daughters’ households is not significantly associated with the outcome variables in this sample of urban Maya families. Instead, maternal anthropometric characteristics and socioeconomic conditions of the family have a greater influence on the overall growth of children.
 
Laboratory setup for administering Bayley III Screening Test
This study investigates how allomaternal care (AMC) impacts human development outside of energetics by evaluating relations between important qualitative and quantitative aspects of AMC and developmental outcomes in a Western population. This study seeks to determine whether there are measurable differences in cognitive and language outcomes as predicted by differences in exposure to AMC via formal (e.g., childcare facilities) and informal (e.g., family and friends) networks. Data were collected from 102 mothers and their typically developing infants aged 13–18 months. AMC predictor data were collected using questionnaires, structured daily diaries, and longitudinal interviews. Developmental outcomes were assessed using the Cognitive, Receptive Language, and Expressive Language subtests of the Bayley III Screening Test. Additional demographic covariates were also evaluated. Akaike Information Criterion (AIC)-informed model selection was used to identify the best-fitting model for each outcome across three working linear regression models. Although AMC variables had no significant effects on Receptive and Expressive Language subtest scores, highly involved familial AMC had a significant medium effect on Cognitive subtest score (β = 0.23, p < 0.01, semi-partial r = 0.28). Formal childcare had no effect on any outcome. This study provides preliminary evidence that there is a measurable connection between AMC and cognitive development in some populations and provides a methodological base from which to assess these connections cross-culturally through future studies. As these effects are attributable to AMC interactions with networks of mostly related individuals, these findings present an area for further investigation regarding the kin selection hypothesis for AMC.
 
In Fig. 2 of the aforementioned article the mean value of the “chair” condition is incorrectly displayed as 0.011 when it should be 0.008. All statistics in the text are correct, and the conclusions remain the same. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
 
Bifactor versus second-order factor model. d = domain specific; f = first-order factor; gen general, r residual (Richardson et al., 2017: Fig. 1)
In this article we attend to recent critiques of psychometric applications of life history (LH) theory to variance among humans and develop theory to advance the study of latent LH constructs. We then reanalyze data (n = 4,244) previously examined by Richardson et al. (Evolutionary Psychology, 15(1), 2017, https://doi.org/10.1177/1474704916666840 to determine whether (a) previously reported evidence of multidimensionality is robust to the modeling approach employed and (b) the structure of LH indicators is invariant by sex. Findings provide further evidence that a single LH dimension is implausible and that researchers should cease interpreting K-factor scores as empirical proxies for LH speed. In contrast to the original study, we detected a small inverse correlation between mating competition and Super-K that is consistent with a trade-off. Tests of measurement invariance across the sexes revealed evidence of metric invariance (i.e., equivalence of factor loadings), consistent with the theory that K is a proximate cause of its indicators; however, evidence of partial scalar invariance suggests use of scores likely introduces bias when the sexes are compared. We discuss limitations and identify approaches that researchers may use to further evaluate the validity of the K-factor and other applications of LH to human variation.
 
Aspects of human life history and cognition, such as our long childhoods and extensive use of teaching, theoretically evolved to facilitate the acquisition of complex tasks. The present paper empirically examines the relationship between subsistence task difficulty and age of acquisition, rates of teaching, and rates of oblique transmission among Hadza and BaYaka foragers from Tanzania and the Republic of Congo. We further examine cross-cultural variation in how and from whom learning occurred. Learning patterns and community perceptions of task difficulty were assessed through interviews. We found no relationship between task difficulty, age of acquisition, and oblique transmission, and a weak but positive relationship between task difficulty and rates of teaching. While same-sex transmission was normative in both societies, tasks ranked as more difficult were more likely to be transmitted by men among the BaYaka, but not among the Hadza, potentially reflecting cross-cultural differences in the sexual division of subsistence and teaching labor. Further, the BaYaka were more likely to report learning via teaching, and less likely to report learning via observation, than the Hadza, possibly owing to differences in socialization practices.
 
A fundamental cognitive function found across a wide range of species and necessary for survival is the ability to navigate complex environments. It has been suggested that mobility may play an important role in the development of spatial skills. Despite evolutionary arguments offering logical explanations for why sex/gender differences in spatial abilities and mobility might exist, thus far there has been limited sampling from nonindustrialized and subsistence-based societies. This lack of sampling diversity has left many unanswered questions regarding the effects that environmental variation and cultural norms may have in shaping mobility patterns during childhood and the development of spatial competencies that may be associated with it. Here we examine variation in mobility (through GPS tracking and interviews), performance on large-scale spatial skills (i.e., navigational ability), and performance on small-scale spatial skills (e.g., mental rotation task, Corsi blocks task, and water-level task) among Twa forager/pastoralist children whose daily lives have been dramatically altered since settlement and the introduction of government-funded boarding schools. Unlike in previous findings among Twa adults, boys and girls (N = 88; aged 6–18) show similar patterns of travel on all measures of mobility. We also find no significant differences in spatial task performance by gender for large- or small-scale spatial skills. Further, children performed as well as adults did on mental rotation, and they outperformed adults on the water-level task. We discuss how children’s early learning environments may influence the development of both large- and small-scale spatial skills.
 
Percentage of forager clusters/cultures in the study sample (n = 53) evincing the use of ostensive-communicative behaviors in oral storytelling, by ostensive behavior type and geographic region
Number of North American and non-North American clusters/cultures in the study sample (n = 53) evincing the use of 14 different ostensive communicative behaviors in oral storytelling
Number of different ostensive-communicative behaviors used within clusters/cultures in the study sample (n = 53). All cultures in the sample evinced the use of at least two different ostensive-communicative behaviors in oral storytelling
Teaching is hypothesized to be a species-typical behavior in humans that contributed to the emergence of cumulative culture. Several within-culture studies indicate that foragers depend heavily on social learning to acquire practical skills and knowledge, but it is unknown whether teaching is universal across forager populations. Teaching can be defined ethologically as the modification of behavior by an expert in the presence of a novice, such that the expert incurs a cost and the novice acquires skills/knowledge more efficiently or that it would not acquire otherwise. One behavioral modification hypothesized to be an adaptation for teaching is ostensive communication—exaggerations of prosody and gesture that signal intent to transmit generalizable knowledge and indicate the intended receiver. On this view, the use of ostensive communication in conjunction with the transmission of generalizable knowledge constitutes evidence of teaching. Oral storytelling appears to meet these criteria: Indigenous peoples regard their traditions as important sources of ecological and social knowledge, and oral storytelling is widely reported to employ paralinguistic communication. To test this hypothesis, descriptions of performed narrative in forager societies were coded for the use of 14 ostensive-communicative behaviors and the presence of generalizable knowledge. Although biased toward North America, the study sample comprised 53 forager cultures spanning five continents, 34 language families, and diverse biomes. All cultures evinced the predicted behaviors. Results suggest that foragers use storytelling as a mode of instruction, thus providing cross-cultural evidence of teaching in forager populations.
 
Recent work with infants suggests that plant foraging throughout evolutionary history has shaped the design of the human mind. Infants in Germany and the US avoid touching plants and engage in more social looking toward adults before touching them. This combination of behavioral avoidance and social looking strategies enables safe and rapid social learning about plant properties within the first two years of life. Here, we explore how growing up in a context that requires frequent interaction with plants shapes children’s responses with the participation of communities in rural Fiji. We conducted two interviews with adults and a behavioral study with children. The adult interviews map the plant learning landscape in these communities and provide context for the child study. The child study used a time-to-touch paradigm to examine whether 6- to 48-month-olds (N = 33) in participating communities exhibit avoidance behaviors and social looking patterns that are similar to, or different from, those of German and American infants. Our adult interview results confirmed that knowledge about daily and medicinal uses of plants is widely known throughout the communities, and children are given many opportunities to informally learn about plants. The results of the child behavioral study suggest that young Fijian children, like German and American infants, are reluctant to reach for novel artificial plants and are fastest to interact with familiar household items and shells. In contrast to German and American infants, Fijian children also quickly reached for familiar real plants and did not engage in differential social looking before touching them. These results suggest that cultural contexts flexibly shape the development of plant-relevant cognitive design.
 
Hunter-gatherer subsistence tasks stratified by skill and strength. Tasks are not exhaustive; placement is qualitative and relative
Savanna Pumé children at work, play and learning. Top row L to R: a mixed-sex group of 3- to 5-year-olds cooking roots after collecting them from the edge of camp; b 6- to 10-year-olds constructing a miniature house (girls not in picture); c 12-year-old boy caring for a cousin with his younger siblings; d 12-year-old boy and girl and young cousins helping to thatch house (little boys handing palm thatch to older children, who pass them to adults on the roof, who are securing the leaves). Bottom row L to R: e 3-year-old boy practicing with child’s bow, getting ready to shoot lizards; f mixed-sex group of 2- to 12-year-olds playing on whirligig; g 2-year-old boy playing with machete; h 9-year-old boy watching his uncle make an axe handle. Photo credits: Russell D. Greaves
Time allocation budgets for Savanna Pumé children ages 3–16. Each bar represents a child, with sex and age identified. See text for activity codes. Time allocated to each activity is given as the proportion of total scan observations per individual (mean = 298 ± 12)
Time allocation budgets for Savanna Pumé children aggregated by age group. Time allocated to each activity is given as the proportion of the total scan observations recorded per age group
The time that children allocate to subsistence tasks (line) and return rates (markers) for common resources, both given as the proportion of the adult mean for (a) girls and (b) boys. Markers show individual data points for return rates (see “Analytic Approach” for details), and line shows the loess smooth of time allocated to subsistence tasks as a proportion of the adult mean
Research in nonindustrial small-scale societies challenges the common perception that human childhood is universally characterized by a long period of intensive adult investment and dedicated instruction. Using return rate and time allocation data for the Savanna Pumé, a group of South American hunter-gatherers, age patterns in how children learn to become productive foragers and from whom they learn are observed across the transition from childhood to adolescence. Results show that Savanna Pumé children care for their siblings, are important economic contributors, learn by doing rather than by instruction, and spend their time principally in the company of other children. This developmental experience contrasts with that of children in postindustrial societies, who are dependent on adults, often well past maturity; learn in formal settings; and spend much of their time in the company of adults. These differences raise questions about whether normative behaviors observed in postindustrial societies are representative of human children. This comparison also identifies the potential mismatch between hunter-gatherer and postindustrial societies in the extent to which children may be well adapted to learn from and teach each other. In particular, spending time in autonomous work and play groups develops the cooperation and coordination skills that are foundational to human subsistence and growing up to be socially and productively adept adults and parents.
 
Top-cited authors
Steven W Gangestad
  • University of New Mexico
Randy Thornhill
  • University of New Mexico
Elizabeth Cashdan
  • University of Utah
Aurelio José Figueredo
  • The University of Arizona
Barbara H. Brumbach
  • Oregon Health and Science University