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Data, Materials, and Software Availability: All study data are included in the article and/or supporting information available online at https://www.pnas.org/lookup/doi/10.1073/pnas.2220124120#supplementary-materials . Copyright © 2023 the Author(s). To address claims of human exceptionalism, we determine where humans fit within the greater mammalian distribution of reproductive inequality. We show that humans exhibit lower reproductive skew (i.e., inequality in the number of surviving offspring) among males and smaller sex differences in reproductive skew than most other mammals, while nevertheless falling within the mammalian range. Additionally, female reproductive skew is higher in polygynous human populations than in polygynous nonhumans mammals on average. This patterning of skew can be attributed in part to the prevalence of monogamy in humans compared to the predominance of polygyny in nonhuman mammals, to the limited degree of polygyny in the human societies that practice it, and to the importance of unequally held rival resources to women’s fitness. The muted reproductive inequality observed in humans appears to be linked to several unusual characteristics of our species—including high levels of cooperation among males, high dependence on unequally held rival resources, complementarities between maternal and paternal investment, as well as social and legal institutions that enforce monogamous norms. This work was conducted as a part of the “Emergence of Hierarchy and Leadership in Mammalian Societies” group at the National Institute for Mathematical and Biological Synthesis, supported by NSF Award DBI-1300426 and the University of Tennessee, Knoxville. It was supported by NSF awards SMA-1329089 and SMA-1743019, and the Santa Fe Institute, as well as the Max Planck Institute for Evolutionary Anthropology, Department of Human Behavior, Ecology and Culture. S.G. was supported by the US Army Research Office grants W911NF-14-1-0637, W911NF-17-1-0150, and the Office of Naval Research grant W911NF-18-1-0138. Additional funding for data collection was provided by the Wenner-Gren Foundation for Anthropological Research awards: 8913 and 7970, by NSF awards: BCS-0924630, BCS-0925910, BCS-0848360, BCS-0514559, BCS-0613226, BCS-0827277, SES-9870429, and DDRIG-1357209, by the National Geographic Society awards: HJ-099R-17, 20113909, 8671-09, and 7968-06, by the Kone Foundation awards: 086809, 088423, and 088423, and by the Jacobs Foundation, the UCSB Broom Center for Demography, and the UCSB Department of Anthropology.

Research on emotion communication typically focuses on facial expressions, yet scientists dating back to Darwin have noted the importance of the body in conveying emotions. In fact, studies have found that the body is reliably used to express and recognize anger, fear, and sadness, by individuals in several industrialized populations. Here, we provide the first evidence that bodily expressions of these three emotions are reliably recognized by members of an isolated small-scale traditional society: the Mayangna of Nicaragua. Specifically, we found that recognition rates for sadness and anger bodily expressions were high, and recognition rates for a fear bodily expression were lower but still significantly greater than chance. Given that the Mayangna are unlikely to have learned these bodily expressions through cross-cultural transmission, their ability to recognize these displays provides strong evidence for the universality of each expression. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s42761-021-00052-y.

Funder: Max Planck Institute for Evolutionary Anthropology (2), A key issue distinguishing prominent evolutionary models of human life history is whether prolonged childhood evolved to facilitate learning in a skill- and strength-intensive foraging niche requiring high levels of cooperation. Considering the diversity of environments humans inhabit, children's activities should also reflect local social and ecological opportunities and constraints. To better understand our species' developmental plasticity, the present paper compiled a time allocation dataset for children and adolescents from twelve hunter-gatherer and mixed-subsistence forager societies (n = 690; 3-18 years; 52% girls). We investigated how environmental factors, local ecological risk, and men and women's relative energetic contributions were associated with cross-cultural variation in child and adolescent time allocation to childcare, food production, domestic work, and play. Annual precipitation, annual mean temperature, and net primary productivity were not strongly associated with child and adolescent activity budgets. Increased risk of encounters with dangerous animals and dehydration negatively predicted time allocation to childcare and domestic work, but not food production. Gender differences in child and adolescent activity budgets were stronger in societies where men made greater direct contributions to food production than women. We interpret these findings as suggesting that children and their caregivers adjust their activities to facilitate the early acquisition of knowledge which helps children safely cooperate with adults in a range of social and ecological environments. These findings compel us to consider how childhood may have also evolved to facilitate flexible participation in productive activities in early life.

The multilevel social relations model (SRM) is a commonly used statistical method for the analysis of social networks. In this article and accompanying supplemental materials, we demonstrate the estimation and interpretation of the SRM using Stat-JR software. Multiple software templates permit the analysis of different response types, including binary, counts, and continuous responses.

As the world's most ubiquitous carnivore, domestic dogs maintain unique proximity to human populations. Partly because dogs potentially serve as hosts of zoonotic diseases, determinants of canine health are increasingly the focus of interdisciplinary research. Emerging perspectives suggest that dogs' health may vary as a function of their owners' wealth and financial resources, a correlation that could potentially inform public health programs and conservation efforts. The objective of this study was to evaluate associations between household wealth and the health of domestic dogs (n = 208) among indigenous Mayangna communities in the Bosawás Biosphere Reserve, Nicaragua. The dogs were evaluated using serum biochemistry, complete blood count, and physical exam findings. Using these data, a principal components analysis (PCA) determined the presence of four "syndromes": 1) decreased body condition score (BCS) & hypoalbuminemia; 2) lymphocytosis & eosinophilia; 3) segmented neutrophilia; and 4) lymphadenopathy, tick infestation, & hyperglobulinemia. An inventory of possessions indexed household wealth. For all four syndromes, household wealth was a weak and uninformative predictor of the dogs' health. The few differences seen among dogs from households with different degrees of wealth likely reflect that nearly all dogs had marginal health and all households were relatively poor. Results from this study imply that owners' wealth may have diverse effects on canine health in rural settings.

The present pre-registered research provides the first evidence that a downwards head tilt is sufficient to communicate dominance from a neutral facial expression among the Mayangna, members of an unindustrialized, small-scale traditional society in Nicaragua who have had minimal exposure to North American culture. Consistent with the Action Unit imposter effect observed in North American populations (Witkower and Tracy in Psychol Sci 30:893–906, 2019), changes to the appearance of the upper face caused by a downwards head tilt were sufficient to elicit perceptions of dominance among this population. Given that the Mayangna are unlikely to associate a downwards head tilt or related apparent facial changes with dominance as a result of cross-cultural learning, the present results suggest that perceptions of dominance formed from a downwards head tilt, and the visual illusion shaping these perceptions, are a widely generalizable, and possibly universal, feature of human psychology.

Across multiple species of social mammals, a growing number of studies have found that that individual sociality is associated with survival. In long-lived species, like primates, lifespan is one of the main components of fitness. We used 18 years of data from the Lomas Barbudal Monkey project to quantify social integration in 11 capuchin (Cebus capucinus) groups and tested whether female survivorship was associated with females’ tendencies to interact with three types of partners: (1) all group members, (2) adult females, (3) adult males. We found strong evidence that females who engaged more with other females in affiliative interactions and foraged in close proximity experienced increased survivorship. We found some weak evidence that females might also benefit from engaging in more support in agonistic contexts with other females. These benefits were evident in models that account for the females’ rank and group size. Female interactions with all group members also increased survival, but the estimates of the effects were more uncertain. In interactions with adult males, only females who provided more grooming to males survived longer. The results presented here suggest that social integration may result in survival-related benefits. Females might enjoy these benefits through exchanging grooming for other currencies, such as coalitionary support or tolerance.

There exists a paucity of evolution-oriented research focusing on why relationships end, particularly in comparison to the substantial literature centered around individual preferences that define the beginning of relationships. In contrast, there is a long tradition in the fields of sociology and family studies of exploring divorce, however, this body of research is largely limited to studies of Western populations. We address these gaps in the literature with an examination of patterns of divorce among a small-scale horticultural population in Nicaragua. We test a number of hypotheses derived from behavioral ecology perspective regarding the timing and causes of divorce. Results lend support to all but one of the hypotheses. Overall divorce rates are comparable to U.S. rates, however, they tend to occur earlier in marriages. Children appear to provide a slight buffering effect against divorce, although age in marriage does not. Gender differences in the reported causes of divorce fall along the lines that would be expected due to differences in partner preferences reported in previous research. Finally, this population also exhibits a similar peculiar pattern exhibited by Western populations, in which divorce is more costly for women, and yet women are slightly more likely to initiate divorces than husbands.

Studies of dogs have proliferated among canine scientists, aided in part by the logistical convenience of working with owned animals whose care is handled by others. These pet dogs are unlike most dogs that have lived in contemporary or prehistoric settings. In particular, many of the dogs studied by canine scientists are NATIVE dogs: (1) neutered, (2) alimented, (3) trained, (4) isolated, (5) vaccinated, and (6) engineered. The distinct genotypes and unusual environments of NATIVE dogs stand in contrast to the characteristics of dogs who have adapted to lives in other human communities and settings. For a holistic perspective on the evolution of dogs, it is helpful to study dogs in environments that share features of the settings in which dogs evolved.

The rich history and global abundance of domestic dogs (Canis familiaris) present a unique opportunity and an ideal model for interdisciplinary research. Canine evolutionary history demonstrates unprecedented changes across all levels of biological organization. These include diversification from highly social, pack-dwelling wild carnivores (extant gray wolves, C. lupus), to increased dependence on humans (domestication), to modern in-home colonization featuring close physical proximity to humans (interspecies bonding). The young, emerging field of “canine science” comprises diverse biological disciplines including evolution, genetics, cognition, behavior, physiology, comparative medicine, and ecology, drawing on studies of both natural and experimental systems and scaling across all levels of biological organization, from genomes to ecosystems. However, limited connections bridge the various fields associated with canine science, although in every branch it is recognized that this species is one of the most phenotypically variable mammals. Yet there has been growing interest in integrating the insights from genomic evolution with those from ecophysiology and ecology, thus facilitating a more biologically comprehensive perspective of dogs. In particular, integrative, mechanistic, and/or ecological studies have been generally underrepresented. To address these emerging interests, we have collected the most compelling questions in the field of canine biology and present avenues of current and future research. This paper serves to both orient the reader to this special issue, as well as offer a forward-looking perspective from diverse biological sub-disciplines to highlight current and future goals in canine research.

Researchers often use moral dilemmas to investigate the specific factors that influence participants’ judgments of the appropriateness of different actions. A common construction of such a dilemma is the Trolley Problem, which pits an obvious utilitarian solution against a common deontological dictum to not do harm to others. Cross-cultural studies have validated the robustness of numerous contextual biases, such as judging utilitarian decisions more negatively if they require contact with other individuals (contact bias), they force others to serve as a means to an end (means bias), and if they require direct action rather than inaction (omission bias). However, such cross-cultural research is largely limited to studies of industrialized, nation-state populations. Previous research has suggested that the more intimate community relationships that characterize small-scale populations might lead to important differences, such as an absence of an omission bias. Here we contribute to this literature by investigating perceptions of Trolley Problem solutions among a Mayangna/Miskito community, a small-scale indigenous population in Nicaragua. Compared to previously sampled populations, the Mayangna/Miskito participants report higher levels of acceptance of utilitarian solutions and do not exhibit an omission bias. We also examine the justifications participants offered to explore how Mayangna/Miskito culture might influence moral judgments.

Humans have long possessed an extensive, intimate relationship to the domesticated dog, and cultures around the world today continue to rely on dogs to carry out vital tasks, including hunting, guarding, and transportation. Thus, it is important to understand the dynamics that play into a dog’s ability to carry out human-assigned tasks. Cortisol is a glucocorticoid hormone which plays a critical role in a number of regulatory functions in the body and is often analyzed to assess aspects of health, stress response, and growth and reproduction. Current published research on cortisol in dogs has been relatively limited, leaving a need for larger-scale studies to assess whether current understandings of how cortisol acts in dogs is applicable to dogs within dynamic and heterogeneous environments. This study examines the relationships between hair cortisol concentrations (HCC) and sex, nutritional status (as determined by body condition scores, or BCS), and body mass (geometric mean calculated from morphometric measurements), as well as the potential influence of hair pigmentation (light, dark, or agouti/mixed) on HCC in domesticated Nicaraguan hunting dogs of the Bosawas Biosphere Reserve. The dogs examined in this study live in a marginal environment where disease, malnutrition, and mortality rates are high. For fur color, HCC was significantly higher in light fur than in than dark and mixed fur (p

The study of moral dilemmas enables researchers to investigate the specific factors that influence humans’ judgments of the appropriateness of different actions. A common construction of this dilemma is the so-called Trolley Problem, which pits an obvious utilitarian solution, one which saves the largest number of lives, against a common deontological dictum to not do harm to others. Participants vacillate on their preferred preferences based on a number of well-documented contextual factors. Although the literature is replete with cross-cultural studies validating the robustness of such biases, the sampled cultural variation within this literature is largely limited to Western, industrialized, educated, rich, and democratic (WEIRD) populations. Here we expand this variation by investigating preferred solutions to common Trolley Problem scenarios among a Mayangna community, a small-scale indigenous population residing in northern Nicaragua. Compared to previously sampled populations, the Mayangna participants report much higher levels of acceptance of utilitarian solutions. Furthermore, while some tests suggest a contact/means bias, there is no evidence of an omission bias. We examine spontaneously reported justifications to explore how Mayangna culture might lead participants to take into account considerations that are largely absent in WEIRD populations.

Hunters exhibit high skill across the life span, individuals vary substantially in skill, and age-related peaks vary across sites., Human adaptation depends on the integration of slow life history, complex production skills, and extensive sociality. Refining and testing models of the evolution of human life history and cultural learning benefit from increasingly accurate measurement of knowledge, skills, and rates of production with age. We pursue this goal by inferring hunters’ increases and declines of skill from approximately 23,000 hunting records generated by more than 1800 individuals at 40 locations. The data reveal an average age of peak productivity between 30 and 35 years of age, although high skill is maintained throughout much of adulthood. In addition, there is substantial variation both among individuals and sites. Within study sites, variation among individuals depends more on heterogeneity in rates of decline than in rates of increase. This analysis sharpens questions about the coevolution of human life history and cultural adaptation.

Becoming valuable to fellow group members so that one would attract assistance in times of need is a major adaptive problem. To solve it, the individual needs a predictive map of the degree to which others value different acts so that, in choosing how to act, the payoff arising from others’ valuation of a potential action (e.g., showing bandmates that one is a skilled forager by pursuing a hard-to-acquire prey item) can be added to the direct payoff of the action (e.g., gaining the nutrients of the prey captured). The pride system seems to incorporate all of the elements necessary to solve this adaptive problem. Importantly, data from western(-ized), educated, industrialized, rich, and democratic (WEIRD) societies indicate close quantitative correspondences between pride and the valuations of audiences. Do those results generalize beyond industrial mass societies? To find out, we conducted an experiment among 567 participants in 10 small-scale societies scattered across Central and South America, Africa, and Asia: (i) Bosawas Reserve, Nicaragua; (ii) Cotopaxi, Ecuador; (iii) Drâa-Tafilalet, Morocco; (iv) Enugu, Nigeria; (v) Le Morne, Mauritius; (vi) La Gaulette, Mauritius; (vii) Tuva, Russia; (viii) Shaanxi and Henan, China; (ix) farming communities in Japan; and (x) fishing communities in Japan. Despite widely varying languages, cultures, and subsistence modes, pride in each community closely tracked the valuation of audiences locally (mean r = +0.66) and even across communities (mean r = +0.29). This suggests that the pride system not only develops the same functional architecture everywhere but also operates with a substantial degree of universality in its content.

Long-lasting, romantic partnerships are a universal feature of human societies, but almost as ubiquitous is the risk of instability when one partner strays. Jealous response to the threat of infidelity is well studied, but most empirical work on the topic has focused on a proposed sex difference in the type of jealousy (sexual or emotional) that men and women find most upsetting, rather than on how jealous response varies(1,2). This stems in part from the predominance of studies using student samples from industrialized populations, which represent a relatively homogenous group in terms of age, life history stage and social norms(3,4). To better understand variation in jealous response, we conducted a 2-part study in 11 populations (1,048 individuals). In line with previous work, we find a robust sex difference in the classic forced-choice jealousy task. However, we also show substantial variation in jealous response across populations. Using parental investment theory, we derived several predictions about what might trigger such variation. We find that greater paternal investment and lower frequency of extramarital sex are associated with more severe jealous response. Thus, partner jealousy appears to be a facultative response, reflective of the variable risks and costs of men’s investment across societies.

A hypothesis for the evolution of long post-reproductive lifespans in the human lineage involves asymmetries in relatedness between young immigrant females and the older females in their new groups. In these circumstances, inter-generational reproductive conflicts between younger and older females are predicted to resolve in favour of the younger females, who realize fewer inclusive fitness benefits from ceding reproduction to others. This conceptual model anticipates that immigrants to a community initially have few kin ties to others in the group, gradually showing greater relatedness to group members as they have descendants who remain with them in the group. We examine this prediction in a cross-cultural sample of communities, which vary in their sex-biased dispersal patterns and other aspects of social organization. Drawing on genealogical and demographic data, the analysis provides general but not comprehensive support for the prediction that average relatedness of immigrants to other group members increases as they age. In rare cases, natal members of the community also exhibit age-related increases in relatedness. We also find large variation in the proportion of female group members who are immigrants, beyond simple traditional considerations of patrilocality or matrilocality, which raises questions about the circumstances under which this hypothesis of female competition are met. We consider possible explanations for these heterogenous results, and we address methodological considerations that merit increased attention for research on kinship and reproductive conflict in human societies.This article is part of the theme issue ‘The evolution of female-biased kinship in humans and other mammals’.

A common assumption is that individuals continue to accumulate ethnobiological knowledge throughout their lives, resulting in greater expertise among the elder generations. Alternative theoretical perspectives suggest that ethnobiological knowledge about animals should peak earlier in life, paralleling and facilitating the emergence of foraging proficiency among younger adults. We test these competing models among indigenous Nicaraguans with three measures of knowledge about fish behavior. Our results indicate that individuals exhibit considerable domain knowledge as relatively young adults. There is also a positive correlation between some measures of knowledge and fishing ability, suggesting that knowledge may promote and develop from specialization and the allocation of effort to fishing. These results imply a model of humans as flexible learners, assimilating ethnobiological knowledge via social learning and related experiences. Contrary to conventional perspectives, we suggest that age-related variat...

Author(s): Ross, Cody T; Mulder, Monique Borgerhoff; Oh, Seung-Yun; Bowles, Samuel; Beheim, Bret; Bunce, John; Caudell, Mark; Clark, Gregory; Colleran, Heidi; Cortez, Carmen; Draper, Patricia; Greaves, Russell D; Gurven, Michael; Headland, Thomas; Headland, Janet; Hill, Kim; Hewlett, Barry; Kaplan, Hillard S; Koster, Jeremy; Kramer, Karen; Marlowe, Frank; McElreath, Richard; Nolin, David; Quinlan, Marsha; Quinlan, Robert; Revilla-Minaya, Caissa; Scelza, Brooke; Schacht, Ryan; Shenk, Mary; Uehara, Ray; Voland, Eckart; Willfuhr, Kai; Winterhalder, Bruce; Ziker, John | Abstract: With apologies, an incorrect author list was given in the article. An additional author, Chris von Rueden, (Jepson School of Leadership Studies, University of Richmond) also contributed to this work. Author Ryan Schacht's affiliation was out-of-date. His correct affiliation is: Department of Anthropology, East Carolina University.

© 2018 The Author(s) Published by the Royal Society. All rights reserved. Monogamy appears to have become the predominant human mating system with the emergence of highly unequal agricultural populations that replaced relatively egalitarian horticultural populations, challenging the conventional idea - based on the polygyny threshold model - that polygyny should be positively associated with wealth inequality. To address this polygyny paradox, we generalize the standard polygyny threshold model to a mutual mate choice model predicting the fraction of women married polygynously. We then demonstrate two conditions that are jointly sufficient to make monogamy the predominant marriage form, even in highly unequal societies. We assess if these conditions are satisfied using individual-level data from 29 human populations. Our analysis shows that with the shift to stratified agricultural economies: (i) the population frequency of relatively poor individuals increased, increasing wealth inequality, but decreasing the frequency of individuals with sufficient wealth to secure polygynous marriage, and (ii) diminishing marginal fitness returns to additional wives prevent extremely wealthy men from obtaining as many wives as their relative wealth would otherwise predict. These conditions jointly lead to a high population-level frequency of monogamy.

For individuals, status is derived both from their personal attributes and the groups with whom they are affiliated. Depending on the performance of their groups, the status of individuals may benefit or suffer from identifying closely with the group. When the group excels, high-status members potentially receive much of the credit and increased status. Conversely, high-status members of underperforming groups potentially suffer disproportionate declines in their status relative to the low-status group members. We therefore predict an interaction between group performance and individual status on the willingness to associate with the group and its members. We test our prediction by examining social media ties among teammates in the National Basketball Association. Specifically, we investigate the "following" ties of teammates on Twitter at the end of the 2014-2015 season. Elections to All-Star games are used to measure the status of players, and team performance is measured by recent success in the postseason playoffs. The results show that compared to high-status players on successful teams, high-status players on underperforming teams are less likely to follow their teammates. This result aligns with research on status inconsistency, suggesting that individuals deemphasize their group affiliation when it jeopardizes their individual status. An additional contribution is the advancement of the probit Social Relations Model for the analysis of binary ties in social networks.

Among social mammals, humans uniquely organize themselves into communities of households that are centred around enduring, predominantly monogamous unions of men and women. As a consequence of this social organization, individuals maintain social relationships both within and across households, and potentially there is conflict among household members about which social ties to prioritize or de-emphasize. Extending the logic of structural balance theory, I predict that there will be considerable overlap in the social networks of individual household members, resulting in a pattern of group-level reciprocity. To test this prediction, I advance the Group-Structured Social Relations Model, a generalized linear mixed model that tests for group-level effects in the inter-household social networks of individuals. The empirical data stem from social support interviews conducted in a community of indigenous Nicaraguan horticulturalists, and model results show high group-level reciprocity among households. Although support networks are organized around kinship, covariates that test predictions of kin selection models do not receive strong support, potentially because most kin-directed altruism occurs within households, not between households. In addition, the models show that households with high genetic relatedness in part from children born to adulterous relationships are less likely to assist each other.

Behavioral ecologists have recently begun using multilevel modeling for the analysis of social behavior. We present a multilevel modeling formulation of the Social Relations Model that is well suited for the analysis of dyadic network data. This model, which we adapt for count data and small datasets, can be fitted using standard multilevel modeling software packages. We illustrate this model with an analysis of meal sharing among Ye'kwana horticulturalists in Venezuela. In this setting, meal sharing among households is predicted by an association index, which reflects the amount of time that members of the households are interacting. This result replicates recent findings that interhousehold food sharing is especially prevalent among households that interact and cooperate in multiple ways. We discuss opportunities for human behavioral ecologists to expand their focus to the multiple currencies and cooperative behaviors that characterize interpersonal relationships in preindustrial societies. We discuss possible extensions to this statistical modeling approach and applications to research by human behavioral ecologists and primatologists. Am J Phys Anthropol 157:507–512, 2015. © 2015 Wiley Periodicals, Inc.

Behavioral ecologists frequently use observational methods, such as instantaneous scan sampling, to record the behavior of animals at discrete moments in time. We develop and apply multilevel, multinomial logistic regression models for analyzing such data. These statistical methods correspond to the multinomial character of the response variable while also accounting for the repeated observations of individuals that characterize behavioral datasets. Correlated random effects potentially reveal individual-level trade-offs across behaviors, allowing for models that reveal the extent to which individuals who regularly engage in one behavior also exhibit relatively more or less of another behavior. Using an example dataset, we demonstrate the estimation of these models using Hamiltonian Monte Carlo algorithms, as implemented in the RStan package in the R statistical environment. The supplemental files include a coding script and data that demonstrate auxiliary functions to prepare the data, estimate the models, summarize the posterior samples, and generate figures that display model predictions. We discuss possible extensions to our approach, including models with random slopes to allow individual-level behavioral strategies to vary over time and the need for models that account for temporal autocorrelation. These models can potentially be applied to a broad class of statistical analyses by behavioral ecologists, focusing on other polytomous response variables, such as behavior, habitat choice, or emotional states. Electronic supplementary material The online version of this article (doi:10.1007/s00265-017-2363-8) contains supplementary material, which is available to authorized users.

Dietary reconstruction via stable isotope analysis is an important part of the study of past populations, but can raise issues in many parts of the world where human remains are scarce, absent, or restricted due to ethical concerns. Given these issues, some researchers have used domesticated dogs as human dietary proxies via the Canine Surrogacy Approach (CSA). We performed carbon and nitrogen stable isotope analysis on the hair of 304 humans and 57 dogs from 45 households in two contemporary indigenous communities in Nicaragua’s Bosawas Biosphere Reserve to explore whether dogs function as dietary proxies for their human owners in this Neotropical horticulturalist context. While CSA is broadly viable at these study sites, on a more precise scale the diets of dogs do not reflect the diets of their owners. This raises questions about the applicability of CSA to archaeological contexts, suggesting that relying on dogs as dietary proxies may overlook key variation in past human diets.

When adult males are temporarily away from the household,observational evidence suggests cross-culturaland intra-cultural variation in the effects of their absence on the labor ofother householdmembers.Insubsistence-based econ- omies, we predict that other adolescent or older members will work more in essential production activities that otherwise would be performed by the missing men. We test this hypoth- esis using spot-check time allocation datasets from rural Nicaragua and Peru and the methodology of mixed-effects statistical models. In Nicaragua, we find that the absence of male household heads rarely necessitates substitute labor by household co-residents, apparently because men typically time their absences to coincide with the non-peak agricultural season. In Peru, the absence of male household heads results in increased men's work by co-residents only under unusual circumstances, as households apparently rely on other strate- gies to mitigate for the loss of labor. In addition to the com- parative empirical analysis of the two cases, we show how mixed-effects models allow for individual heterogeneity and data structures that confound more familiar statistical techni- ques and occasionally produce spurious results. Mixed-effects modeling techniques will be necessary if we are to realize the analytic potential of the extensive, standardized time al- location datasets gathered by anthropologists.

Given the complexity of human foraging strategies, especially hunting, recent attention has focused on the ways in which hunters acquire needed knowledge and skills, including via social learning. One potentially useful heuristic is a “conformist bias,” in which individuals identify and adopt the most common beliefs or strategies, but the usefulness of this heuristic depends on the accuracy of the information. In this study, 45 indigenous Mayangna and Miskito informants in Nicaragua were asked to rank 17 game species on the extent to which harvests of these species are associated with the use of hunting dogs. Consensus analysis indicates that there is high agreement on the rankings, and the aggregated rankings closely reflect harvest data from a yearlong study that documented the use of dogs and other hunting accessories (e.g., firearms). There were noteworthy outliers in the analysis, however, and a possible explanation is that informants are inferring that dogs are useful for some species because they are valuable for hunting perceptually similar species, as revealed by pile sort data. In addition, the consensus analysis reveals sex-related subgroup agreement in the rankings, but the aggregated rankings of neither men nor women seem to more closely correspond to the harvest data. Overall, these results suggest that a conformist learning bias could allow novice hunters to acquire information that would promote optimizing hunting strategies.

Recent analyses of food sharing in small-scale societies indicate that reciprocal altruism maintains interhousehold food transfers, even among close kin. In this study, matrix-based regression methods are used to test the explanatory power of reciprocal altruism, kin selection, and tolerated scrounging. In a network of 35 households in Nicaragua's Bosawas Reserve, the significant predictors of food sharing include kinship, interhousehold distance, and reciprocity. In particular, resources tend to flow from households with relatively more meat to closely related households with little, as predicted by kin selection. This generalization is especially true of household dyads with mother-offspring relationships, which suggests that studies of food sharing may benefit from distinctions between lineal and collateral kin. Overall, this analysis suggests that exchanges among kin are primarily associated with differences in need, not reciprocity. Finally, although large game is distributed widely, qualitative observations indicate that hunters typically do not relinquish control of the distribution in ways predicted by costly signaling theory.

In preindustrial societies, kin may exert influence on the mating choices of women, but there have been few systematic studies of the preferred characteristics of husbands for female kin. In an indigenous Mayangna and Miskito community, photographs of 29 male household heads were presented to informants, who ranked the men on three characteristics: desirability as a spouse, hunting ability and wealth. For the desirability rankings, informants were asked to consider the advice that they would give to young female relatives and rank the men based on the qualities that such women should seek in a husband. Consensus analysis indicates that there is high agreement among informants on all three sets of rankings. There is no evidence that the age and sex of informants are associated with variation in evaluations of the desirability of men, which suggests that the evaluations by reproductively active women do not significantly differ from rankings by other informants. Multivariate analysis indicates that perceptions of both a man's wealth and his hunting ability are positively associated with his desirability as a prospective husband for female kin. By contrast, a strong kin-based social network, as measured by the presence of consanguineal kin in the community, seems unimportant to a man's desirability as a husband. Although it remains unclear to what extent hunting ability is a signal of phenotypic quality, these results support predictions that individuals will encourage female kin to marry men who are good resource providers. Finally, compared to a conventional reliability analysis, consensus analysis is demonstrated as a superior method for assessing both unidimensionality and subgroup variation in informant rankings.

By focusing on the caloric composition of hunted prey species, optimal foraging research has shown that hunters usually make economically rational prey choice decisions. However, research by meat scientists suggests that the gustatory appeal of wildlife meats may vary dramatically. In this study, behavioral research indicates that Mayangna and Miskito hunters in Nicaragua inconsistently pursue multiple prey types in the optimal diet set. We use cognitive methods, including unconstrained pile sorts and cultural consensus analysis, to investigate the hypothesis that these partial preferences are influenced by considerations of meat flavor. Native informants exhibit high agreement on the relative appeal of different meats. Given the absence of other noteworthy differences between spider monkeys (Ateles geoffroyi) and howler monkeys (Alouatta palliata), the unappealing flavor of howler monkeys seems to be a factor in the partial preference for this species.

OBJECTIVES We measured carbon and nitrogen isotopic ratios in a contemporary population, and tested how the isotopic variability relates to measures of socioeconomic status (e.g., household wealth) and anthropometric measures (e.g., standardized height-for-age and weight-for-age z-scores). METHODS Hair samples from individuals living in the Bosawas Biosphere Reserve in Nicaragua were analyzed for δ13 C and δ15 N, and these data were examined in relation to individual (e.g., age, sex, anthropometrics) and household (e.g., household size, wealth) variables. RESULTS We found through mixed-effects modeling that δ13 C and δ15 N varied predictably with individual age and household wealth. δ13 C and δ15 N did not, however, improve models predicting variation in individual anthropometric measures. CONCLUSION These results indicate that, although there is a relationship between diet (δ13 C and δ15 N) and socioeconomic variables, these dietary differences are not the main cause of health differences in this population.

Once absent in much of Amazonia, dogs are now commonly used for hunting throughout the lowland Neotropics. Although some ethnographers have questioned their usefulness, dogs are particularly effective in pursuits of several mammalian prey species. The return rates of hunting with dogs appear to compare favorably with those of hunting with firearms, and dogs may be especially beneficial in anthropogenic habitats. There is considerable cross-cultural variation in the training and care of dogs. Good hunting dogs typically receive better care than their less-talented conspecifics. Mortality rates for dogs in the Neotropics are high, and the causes of death include malnutrition and attacks by other animals. Although isolated Neotropical societies may not have initially recognized the overall value of hunting dogs, a more likely explanation for the absence of dogs in prehistoric Amazonia is the high mortality of dog populations in the region. Additional research is needed to resolve ethnological questions about...

Assessment of the δ 15N ratios and δ 13C isotope values of archaeological dog and human bone collagen, ethnoarchaeological dog bone collagen, and ethnoarchaeological dog and human hair protein demonstrates that these tissues can be used to show subtle differences in diet between households at the same site. While δ 13C isotope values for dog and human bone and hair protein can be used as evidence of C4 photosynthetic plant foods, it is not necessarily an accurate measure for the presence or absence of maize in the diet. Less than 50% of the ethnoarchaeological dog and human samples from households that consumed an average of 0.01 kg of maize per day, had δ 13C isotope values greater than −19%.

Although dogs are used by subsistence hunters in many locations throughout the world, hunters with dogs have not been studied from an optimal foraging perspective. A study of indigenous Mayangna and Miskito hunters in Nicaragua indicates that the use of dogs affects both the encounter rates and the pursuit times of several prey types. Before hunters can identify the prey type and initiate a pursuit, they must first catch up to the dogs, and their dogs sometimes chase unprofitable prey types. These costs are incorporated as an additional constraint in the optimal prey choice model. The results of the optimal foraging analysis indicate that hunters generally focus on prey types that are in the optimal diet set. However, hunters do not consume two rarely encountered species that are in the optimal diet set, giant anteaters and northern tamanduas. Although hunting with both rifles and dogs increases the likelihood of harvesting tapirs, the return rates of hunting with dogs, hunting with rifles, and hunting wi...

SUMMARYAlthough they are used throughout the Neotropics, the impact of dogs on the composition of wildlife harvests has received little systematic attention. In the Bosawas Biosphere Reserve of Nicaragua, indigenous hunters rely heavily on dogs to locate prey. Hunting harvest data over a year-long period in two indigenous Mayangna and Miskito communities indicate that the use of hunting dogs is significantly associated with the harvests of several terrestrial mammalian species. The use of dogs is also a significant predictor of the extent to which the species composition of harvests deviates from Neotropical averages. Although dogs appear to have little effect on the sex profiles of harvested game species, the use of dogs is significantly associated with hunting in agricultural landscapes. From a conservation perspective, the disadvantages of dogs include their indiscriminate pursuit of prey species, including species that hunters would not otherwise pursue. Advantages of dogs include their relative ineffectiveness in pursuits of species that are particularly vulnerable to overhunting, such as primates and white-lipped peccaries (Tayassu pecari). Hunting dogs may be an economical option for many Neotropical societies, and their role in wildlife management plans merits increased attention from conservationists.

Men’s investments in parenting and long-term reproductive relationships are a hallmark feature of human reproduction and life history. The uniqueness of such male involvement among catarrhines has driven an extensive debate surrounding the selective pressures that led to and maintain such capacities in men. Three major pathways have been proposed through which men’s involvement might confer fitness benefits: enhancing child well-being, increasing couple fertility, and decreasing likelihood of partner desertion. Previous research has explored the impact of father involvement on these factors individually, but here we present novel research that explores all three pathways within the same population, the Mayangna/Miskito horticulturalists of Nicaragua. Furthermore, we expand the traditional dichotomous measure of father presence/absence by using a continuous measure of overall male investment, as well as two continuous measures of its subcomponents: direct care and wealth. We find that men’s investments are associated with children’s growth and possibly with wife’s marital satisfaction; however, they are not associated with couple fertility.

Behavioral ecologists have recently begun using multilevel modeling for the analysis of social behavior. We present a multilevel modeling formulation of the Social Relations Model that is well suited for the analysis of dyadic network data. This model, which we adapt for count data and small datasets, can be fitted using standard multilevel modeling software packages. We illustrate this model with an analysis of meal sharing among Ye'kwana horticulturalists in Venezuela. In this setting, meal sharing among households is predicted by an association index, which reflects the amount of time that members of the households are interacting. This result replicates recent findings that interhousehold food sharing is especially prevalent among households that interact and cooperate in multiple ways. We discuss opportunities for human behavioral ecologists to expand their focus to the multiple currencies and cooperative behaviors that characterize interpersonal relationships in preindustrial societies. We discuss possible extensions to this statistical modeling approach and applications to research by human behavioral ecologists and primatologists.

Distributions of human foraging success across age have implications for many aspects of human evolution. Estimating the distribution of foraging returns is complicated by (1) the zero-inflated nature of hunting returns, as many if not most trips fail, and (2) the substantial variation among hunters, independent of age. We develop a multilevel mixture analysis of human foraging data to address these difficulties. Using a previously published 20-year record of hunts by 147 individual Ache hunters in eastern Paraguay, we estimate returns-by-age functions for both hunting failures and the size of harvests, while also estimating the heterogeneity among hunters. Consistent with previous analyses, we find that most hunters peak around 40 years of age. We can also show, however, that much more of the variation among Ache hunters arises from heterogeneity in failure rates (zero returns), not harvest sizes. We also introduce a new R package, glmer2stan, to assist in defining and fitting similar multilevel mixture models.

This report is the first to document giant anteaters (Myrmecophaga tridactyla) in Nicaragua. An indigenous hunter killed four giant anteaters in the Bosawas Biosphere Reserve, Nicaragua. The Mayangna and Miskito residents of the reserve do not eat giant anteaters, but hunters sometimes kill the animals because of the threat they pose to hunting dogs.

Postmarital residence patterns in traditional human societies figure prominently in models of hominid social evolution with arguments for patrilocal human bands similar in structure to female-dispersal systems in other African apes. However, considerable flexibility in hunter-gatherer cultures has led to their characterization as primarily multilocal. Horticulturalists are associated with larger, more sedentary social groups with more political inequality and intergroup conflict and may therefore provide additional insights into evolved human social structures. We analyze coresidence patterns of primary kin for 34 New World horticultural societies (6,833 adults living in 243 residential groupings) to show more uxorilocality (women live with more kin) than found for hunter-gatherers. Our findings further point to the uniqueness of human social structures and to considerable variation that is not fully described by traditional postmarital residence typologies. Sex biases in coresident kin can vary according to the scale of analysis (household vs. house cluster vs. village) and change across the life span, with women often living with more kin later in life. Headmen in large villages live with more close kin, primarily siblings, than do nonheadmen. Importantly, human marriage exchange and residence patterns create meta-group social structures, with alliances extending across multiple villages often united in competition against other large alliances at scales unparalleled by other species. Fil: Walker, Robert S.. University of Missouri; Estados Unidos Fil: Beckerman, Stephen. Pennsylvania State University; Fil: Flinn, Mark V.. University of Missouri; Estados Unidos Fil: Gurven, Michael. University of California; Estados Unidos Fil: von Rueden, Chris R.. University of California; Estados Unidos Fil: Kramer, Karen L.. Harvard University; Estados Unidos Fil: Greaves, Russell D.. Harvard University; Estados Unidos Fil: Córdoba, Lorena Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Villar, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Hagen, Edward H.. Washington State University; Estados Unidos Fil: Koster, Jeremy M.. University Of Cincinnati; Estados Unidos Fil: Sugiyama, Lawrence. University of Oregon; Estados Unidos Fil: Hunter, Tiffany E.. University of Pennsylvania; Estados Unidos Fil: Hill, Kim R.. Arizona State University; Estados Unidos

In past and modern human societies, dogs have played an important role as hunting companions. Given considerable ethnographic evidence that dogs vary in their hunting abilities, this paper addresses the effects of key demographic variables, namely age and sex, on the amount of harvested game that dogs contribute in an indigenous Nicaraguan community. Controlling for variation in the time spent potentially hunting, male dogs and older dogs are significantly associated with greater harvests. These results may account for documented preferences for males in both archaeological and ethnographic contexts. Among societies in which dogs are used both as hunting companions and sources of food, the age-related delay in peak hunting ability also suggests a tradeoff that might explain the consumption of dogs shortly after they have reached adult size. Informant rankings of two cohorts of dogs indicate that residents of the community exhibit high agreement about the relative abilities of the dogs, and the rankings indicate that dogs from the same household exhibit comparable skill. There is little evidence that talented, highly-ranked dogs are provided a more nutritious diet, as measured by nitrogen-based and carbon-based isotopic analysis of hair samples. Overall, although dogs can be quite advantageous as hunting companions, this research suggests that the heterogeneity of hunting ability combines with the high mortality of dogs to impose risks on households that depend on dogs as a source of harvested meat.