Food-Sharing Networks in Lamalera,Indonesia

Exponential random graph modeling (ERGM) is used here to test hypotheses derived from human behavioral ecology about the adaptive nature of human food sharing. Respondents in all (n = 317) households in the fishing and sea-hunting village of Lamalera, Indonesia, were asked to name those households to whom they had more frequently given (and from whom they had more frequently received) food during the preceding sea-hunting season. The responses were used to construct a social network of between-household food-sharing relationships in the village. The results show that kinship, proximity, and reciprocal sharing all strongly increase the probability of giving food to a household. The effects of kinship and distance are relatively independent of each other, although reciprocity is more common among residentially and genealogically close households. The results show support for reciprocal altruism as a motivation for food sharing, while kinship and distance appear to be important partner-choice criteria.     

Factors Affecting Proximity Among Members of a Wild Group of Moor Macaques During Feeding,Moving, and Resting

We studied the effects of kinship, age, sex, and other factors on patterns of spatial proximity among group members in a wild group of moor macaques (Macaca maurus) in Sulawesi, Indonesia. We assessed the importance of each factor via multiple linear regression analyses. Moor macaques stay close to their matrilineal relatives more frequently when the group moves or rests than when they feed. Subjects of similar age, sex, or rank tended to stay close to each other. Females were in the proximity of females with newborn infants regardless of the phase of activity of the group. Kinship may have less effect on proximity during feeding in moor macaques than in Japanese macaques. Weak effects of kinship during feeding may result from weak contest competition for food within the group.     

Net hunters vs. archers: Variation in women's subsistence strategies in the Ituri Forest

BaMbuti of the Ituri Forest, Zaire, employ two primary hunting techniques: net hunting, in which women routinely participate, and bow hunting, in which women rarely participate. We hypothesize that the value of women's labor devoted to different subsistence activities, combined with the exchange value of meat, will determine whether women participate in hunts. Field observations were conducted in four different areas: two exploited by archers and two by net hunters. Results indicate that women in nethunting areas earn more calories per unit time by hunting than by working in agriculturalists' gardens; whereas women in archer areas earn more calories by working for agriculturalists than by hunting. We found no significant difference in the composition or diversity of the forests exploited by net hunters and archers. The results are discussed in light of the longstanding debate concerning the factors that account for distribution of net hunting and archery in the Ituri Forest.     

Social foraging in vampire bats is predicted by long-term cooperative relationships

Stable social bonds in group-living animals can provide greater access to food. A striking example is that female vampire bats often regurgitate blood to socially bonded kin and nonkin that failed in their nightly hunt. Food-sharing relationships form via preferred associations and social grooming within roosts. However, it remains unclear whether these cooperative relationships extend beyond the roost. To evaluate if long-term cooperative relationships in vampire bats play a role in foraging, we tested if foraging encounters measured by proximity sensors could be explained by wild roosting proximity, kinship, or rates of co-feeding, social grooming, and food sharing during 21 months in captivity. We assessed evidence for 6 hypothetical scenarios of social foraging, ranging from individual to collective hunting. We found that closely bonded female vampire bats departed their roost separately, but often reunited far outside the roost. Repeating foraging encounters were predicted by within-roost association and histories of cooperation in captivity, even when accounting for kinship. Foraging bats demonstrated both affiliative and competitive interactions with different social calls linked to each interaction type. We suggest that social foraging could have implications for social evolution if “local” within-roost cooperation and “global” outside-roost competition enhances fitness interdependence between frequent roostmates.

A combination of captive experiments and proximity sensing in the wild show that social bonds in vampire bats that are typically defined by cooperative interactions within the roost also extend beyond the roost and may provide benefits during foraging.     

Quality and quantity of genetic relatedness data affect the analysis of social structure

Kinship plays a fundamental role in the evolution of social systems and is considered a key driver of group living. To understand the role of kinship in the formation and maintenance of social bonds, accurate measures of genetic relatedness are critical. Genotype‐by‐sequencing technologies are rapidly advancing the accuracy and precision of genetic relatedness estimates for wild populations. The ability to assign kinship from genetic data varies depending on a species’ or population's mating system and pattern of dispersal, and empirical data from longitudinal studies are crucial to validate these methods. We use data from a long‐term behavioural study of a polygynandrous, bisexually philopatric marine mammal to measure accuracy and precision of parentage and genetic relatedness estimation against a known partial pedigree. We show that with moderate but obtainable sample sizes of approximately 4,235 SNPs and 272 individuals, highly accurate parentage assignments and genetic relatedness coefficients can be obtained. Additionally, we subsample our data to quantify how data availability affects relatedness estimation and kinship assignment. Lastly, we conduct a social network analysis to investigate the extent to which accuracy and precision of relatedness estimation improve statistical power to detect an effect of relatedness on social structure. Our results provide practical guidance for minimum sample sizes and sequencing depth for future studies, as well as thresholds for post hoc interpretation of previous analyses.     

Bonds of bros and brothers: Kinship and social bonding in postdispersal male macaques

Group‐living animals often maintain a few very close affiliative relationships—social bonds—that can buffer them against many of the inevitable costs of gregariousness. Kinship plays a central role in the development of such social bonds. The bulk of research on kin biases in sociality has focused on philopatric females, who typically live in deeply kin‐structured systems, with matrilineal dominance rank inheritance and life‐long familiarity between kin. Closely related males, in contrast, are usually not close in rank or familiar, which offers the opportunity to test the importance of kinship per se in the formation of social bonds. So far, however, kin biases in male social bonding have only been tested in philopatric males, where familiarity remains a confounding factor. Here, we studied bonds between male Assamese macaques, a species in which males disperse from their natal groups and in which male bonds are known to affect fitness. Combining extensive behavioural data on 43 adult males over a 10‐year period with DNA microsatellite relatedness analyses, we find that postdispersal males form stronger relationships with the few close kin available in the group than with the average nonkin. However, males form the majority of their bonds with nonkin and may choose nonkin over available close kin to bond with. Our results show that kinship facilitates bond formation, but is not a prerequisite for it, which suggests that strong bonds are not restricted to kin in male mammals and that animals cooperate for both direct and indirect fitness benefits.     

Significance of the social relationships of Efe Pygmy men in the Ituri forest,Zaire

Efe Pygmies in northeast Zaire exhibit features of social organization (small group size, flexible but predominantly patrilocal residence, close relations with kin, and pair bonds) that are common to many hunting and gathering societies. This study uses methods commonly employed in studies of nonhuman primates to investigate the associations of Efe men with other individuals as a function of their age, sex, and kinship, and it tests the hypothesis that Efe are patrilocal because hunting efficiency is improved by hunting with male relatives. The analyses of 376 hours of focal behavior observations on 16 Efe men and observations of 71 cooperative group hunts show that the majority of associations between Efe men were with other adult men. Men associated preferentially with kin over nonkin, and they associated with close kin more than with distant kin. Men's close relationships (what we call “Companionships” sensu Smuts' “Friendships” in baboons) were predominantly with other adult men, but each man who cohabited with a woman had his strongest Companionship by far with that woman. Neither the efficiency of hunts nor the hunting success of individual men were found to be related to the degree of relatedness of hunters nor the proportion of relatives on the hunt. Alternative hypotheses concerning the functional significance of patrilocality and male kin groups are considered. We conclude that strong affiliative bonds between male kin and between males and females may arise as much from the need for strong allies in the face of competitive social situations as from economic or ecological necessity.     

Social relationships in a herd of Sorraia horses Part II. Factors affecting affiliative relationships and sexual behaviours

The influence of age, dominance rank, kinship and aggressiveness over affiliative relationships and sexual behaviours were analysed in a herd of Sorraia horses, Equus caballus, kept under extensive management. Subjects were 10 adult mares 5-18 years old that had known each other since birth, and a stallion introduced into the group for breeding for the first time. Kinship coefficient and dominance rank were the most important factors affecting affiliative relationships. Bonds were reciprocal and stronger among mares with higher kinship. Mares spent more time in proximity to close-ranking and lower-ranking females. Mares with stronger affiliative relationships or higher relatedness were not less aggressive towards each other. Affiliative relationships between the stallion and the mares were not reciprocal: lower-ranking mares formed stronger bonds with the stallion but he preferred the less genetically related mares for proximity. However, the stallion was involved in sexual behaviours more frequently with the mares that were more genetically related to him. These results suggest that kinship beyond close relatives may affect affiliative relationships both among familiar and among unfamiliar horses. However, the influence of kinship does not imply that horses possess a kin recognition system and alternative explanations are discussed.     

Women's attractiveness judgments of self-resembling faces change across the menstrual cycle

Two lines of reasoning predict that women's preferences for people exhibiting cues to kinship will be lower in the follicular phase than in the luteal phase of the menstrual cycle. Women may avoid kinship cues during the follicular phase when they are most fertile due to the costs of inbreeding. Alternatively, women may seek kinship cues during the luteal phase as a byproduct of the benefits of associating with kin during pregnancy, which is also characterized by high progesterone. We find that preferences for facial resemblance, a putative kinship cue, follow this predicted pattern and are positively correlated with estimated progesterone levels based on cycle day. Neither estimated estrogen levels nor conception risk predicted preferences for self-resemblance, and the cyclic shift was stronger for preferences for female faces than male faces. These findings lead to the possibility that this cyclic change in preference for self-resemblance may be a byproduct of a hormonal mechanism for increasing affiliative behavior toward kin during pregnancy rather than a mechanism for preventing inbreeding during fertile periods.     

Genetic and Cultural Kinship among the Lamaleran Whale Hunters

The human ability to form large, coordinated groups is among our most impressive social adaptations. Larger groups facilitate synergistic economies of scale for cooperative breeding, such economic tasks as group hunting, and success in conflict with other groups. In many organisms, genetic relationships provide the structure for sociality to evolve via the process of kin selection, and this is the case, to a certain extent, for humans. But assortment by genetic affiliation is not the only mechanism that can bring people together. Affinity based on symbolically mediated and socially constructed identity, or cultural kinship, structures much of human ultrasociality. This paper examines how genetic kinship and two kinds of cultural kinship--affinal kinship and descent--structure the network of cooperating whale hunters in the village of Lamalera, Indonesia. Social network analyses show that each mechanism of assortment produces characteristic networks of different sizes, each more or less conducive to the task of hunting whales. Assortment via close genetic kin relationships (r?=?0.5) produces a smaller, denser network. Assortment via less-close kin relations (r?=?0.125) produces a larger but less dense network. Affinal networks are small and diffuse; lineage networks are larger, discrete, and very dense. The roles that genetic and cultural kinship play for structuring human sociality is discussed in the context of these results.     

The Rebirth of Kinship

Kinship was one of the key areas of research interest among anthropologists in the nineteenth century, one of the most hotly debated areas of theory in the early and mid-twentieth century, and yet an area of waning interest by the end of the twentieth century. Since then, the study of kinship has experienced a revitalization, with concomitant disputes over how best to proceed. This special issue brings together recent studies of kinship by scientific anthropologists employing evolutionary theory and quantitative methods. We argue that the melding of the evolutionary theoretical perspective with quantitative and ethnographic methodologies has strengthened and reinvigorated the study of kinship by synthesizing and extending existing research via rigorous analyses of evidence.     

Kinship and a counter-hegemonic social order: former revolutionaries in southern Oman

Critical reinterpretations of kinship studies questioned earlier ideas that kinship relations reflect and reproduce a dominant social order. ‘New’ kinship studies have nevertheless shown how even non-traditional family forms can reproduce traditional ideas about relatedness, values, and social hierarchies. Promising grounds for resisting ongoing tendencies to link kinship with conservative social reproduction arise from better understanding the circumstances under which kinship relations reproduce a counter-hegemonic social order. Kinship practices of former militants of a defeated revolutionary liberation movement in Dhufar, Oman, make visible veterans’ networks and relations which transgress dominant tribal, ethnic, racial, and gendered hierarchies. These practices show how, even in inauspicious circumstances of political defeat and marginalization, kinship relations can reproduce a counter-hegemonic social order – as well as a social afterlife of defeated revolution.     

Interlocked: kinship,intimate precarity,and plantation labour in India

This article examines the employment of kinship relations in sustaining the plantation economy and in perpetuating the precariousness of child labourers who later became temporary workers in the tea plantations of Kerala, South India. Kinship ties locked diverse workers into a moral obligation of care that could easily be manipulated by plantation management as a form of labour control. Plantation capitalism, therefore, sustained itself not only through overt forms of violence but also through manipulating the precarity of employment in relation to intimate forms of love, care, and obligation that were bound up with kinship ties. Kinship networks of different kinds need to be understood as integral to the plantation society and as occupying a fundamental place within the capitalist order of plantations. I observe that the entangled relationship between workers’ precarity and plantation capitalism can be understood only if we pay attention to what I call the intimate precarity produced by the employment of kinship networks within plantation capitalism.     

Household and Kin Provisioning by Hadza Men

We use data collected among Hadza hunter-gatherers between 2005 and 2009 to examine hypotheses about the causes and consequences of men’s foraging and food sharing. We find that Hadza men foraged for a range of food types, including fruit, honey, small animals, and large game. Large game were shared not like common goods, but in ways that significantly advantaged producers’ households. Food sharing and consumption data show that men channeled the foods they produced to their wives, children, and their consanguineal and affinal kin living in other households. On average, single men brought food to camp on 28% of days, married men without children at home on 31% of days, and married men with children at home on 42% of days. Married men brought fruit, the least widely shared resource, to camp significantly more often than single men. A model of the relationship between hunting success and household food consumption indicates that the best hunters provided 3–4 times the amount of food to their families than median or poor hunters. These new data fill important gaps in our knowledge of the subsistence economy of the Hadza and uphold predictions derived from the household and kin provisioning hypotheses. Key evidence and assumptions backing prior claims that Hadza hunting is largely a form of status competition were not replicated in our study. In light of this, family provisioning is a more viable explanation for why good hunters are preferred as husbands and have higher fertility than others.     

Life Course Perspectives on Women's Autonomy and Health Outcomes

Gender inequality leads to negative demographic consequences in many societies. Patterns of household formation and inheritance strongly influence these consequences. Peasant societies of preindustrial northern Europe emphasized the conjugal bond, while intergenerational bonds were weak. The reverse is true in contemporary northern India. As a result, greater potential exists there for marginalizing women. The convergence of low autonomy due to youth as well as gender means that women's autonomy is at its lowest point during the peak of childbearing years. This has considerable implications for demographic and health outcomes in terms of poorer child survival, slower fertility decline, and poorer reproductive health.     

Mirroring Nature? Men's and Women's Models of Conception in Telefolmin

Telefol men are reluctant to talk about conception, which they claim is ‘bad talk’. Despite this, they espouse a theory of conception, and this theory accords well with the general form of Telefol kinship. Telefol women are cognizant of the men's model, but have a further one of their own which differs from that of the men in regard to the respective contributions of the sexes and the domains in which these contributions are relevant. These domains may be glossed as kinship and cult, and this paper argues that it is the relation between these domains, as well as between women and men, that is the bone of contention.     

Individual contributions to babysitting in a cooperative mongoose, Suricata suricatta

Evolutionary explanations of cooperative breeding based on kin selection have predicted that the individual contributions made by different helpers to rearing young should be correlated with their degree of kinship to the litter or brood they are raising. In the cooperative mongoose or meerkat, Suricata suricatta, helpers babysit pups at the natal burrow for the first month of pup life and frequent babysitters suffer substantial weight losses over the period of babysitting. Large differences in contributions exist between helpers, which are correlated with their age, sex and weight but not with their kinship to the young they are raising. Provision of food to some group members raises the contributions of individuals to babysitting. We discuss the implications of these results for evolutionary explanations of cooperative behaviour.     

KINSHIP MATTERS: WOMEN's LAND CLAIMS IN THE SANTAL PARGANAS, JHARKHAND

This article discusses the strengthening of kinship ties amongst the Santal community in a village in Jharkhand state in India. The context of progressive marginalization from the state and markets has resulted in the Santals asserting their adivasi identity by recourse to customary institutions as well as rigidifying patrilineal rules of inheritance. While this leads generally to an erosion of women's rights to inherit land, under certain circumstances women are supported by kin elders when they bring grievances to the legal courts. Women's relationship to their kinship group thus seems ambiguous: kinship can simultaneously be not only a source of deprivation and suppression but also a way of staking claims to resources, especially in the face of the inadequacies of formal state mechanisms.     

Evolutionary Implications of Persistence Hunting: An Examination of Energy Return on Investment for !Kung Hunting

Hominins are smaller, slower, and weaker than most large mammals, yet they have been eating meat from freshly killed large mammals since before the invention of sophisticated weaponry. It is thought that they could have achieved this seemingly impossible feat through persistence hunting, a practice powered by endurance running. Essentially, one or more hunters pursue a prey animal in the heat of the day until it reaches the point of hyperthermia. This allows a hunter to safely kill the weakened animal at close range using methods such as beating, strangling, or spearing. The energy balance of this approach to getting food is controversial and has not been calculated previously. We examined the energy costs and gains of persistence hunting through several energy returned on investment (EROI) calculations based on synthesizing available field and laboratory data on the energy used by the hunters and the energy returned from the greater kudu (Tragelaphus strepsiceros). We estimate that the EROI of these hunter-gatherers hunting a kudu ranged from 26:1 to 69:1. The net energy gained from such an effort would sustain an average sized !Kung family for 6.7 to 11.2 days. The “profit” energy within these ranges would have supported the early human societies that practiced persistence hunting, contributing to the often-noted “leisure” characterizing many foraging societies (Sahlins 1974).     

The importance of kinship and familiarity in social interactions between mice

We investigated a range of social interactions between mice which differed in their degree of relatedness and familiarity. Unfamiliar half siblings (sharing paternity only) differed significantly from unfamiliar non-siblings (sharing neither mother nor father) in their tendency to perform aggression-related interactions and in the amount of passive body contact they showed. Differences between half and full siblings in patterns of interaction appeared to be due to differing degrees of familiarity with companions. Kinship effects disappeared completely when animals were allowed to become familiar. We discuss the functional significance of the familiarity and kinship effects we found, including differences between the sexes in the types of interaction showing kinship effects. Differences between adult and juvenile mice are also briefly discussed.