No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Older Hadza Men and Women as Helpers
... For example, Wood and Marlowe (2011) show that grandmothers tend to be in camps with their daughters until daughters have teenage daughters of their own. This allows grandmothers to go where their help most increases their inclusive fitness (Jones et al., 2005). This work could perhaps be an indication that females move residence more than men in older age. ...
... Our results also suggest women move marginally more than men later on in life, particularly after their forties. It is possible this later mobility reflects 'mobile grandmothers' moving to provide help, as documented in the anthropological literature (Jones et al., 2005). It is important to emphasise that our results are not directly comparable with the literature on gender differences in mobility that exists in the evolutionary community. ...
Mobility is a major mechanism of human adaptation, both inthe deep past and in the present. Decades of research in the human evolutionary sciences have elucidated how much, how, and when individuals and groups move in response to their ecology. Prior research has focused on small-scale subsistence societies, often in marginal environments and yielding small samples. But adaptive movement is commonplace across human societies, providing an opportunity to study human mobility more broadly. We provide a detailed, life-course structured demonstration, describing the residential mobility system of a historical population living between 1850-1950 in the industrialising Netherlands. We focus on how moves are patterned over the lifespan, attending to individual variation and stratifying our analyses by gender. We conclude that this population was not stationary: the median total moves in a lifetime were 10, with a wide range of variation and an uneven distribution over the life course. Mobility peaks in early adulthood (age 20–30) in this population, and this peak is consistent in all the studied cohorts, and both genders. Mobile populations in sedentary settlements provide a productive avenue for research on adaptive mobility and its relationship to human life history, and historical databases are useful for addressing evolutionarily-motivated questions.
... Matrilocality generally has been considered less prevalent among hunter-gatherers and is associated with particular activities resulting in male absenteeism such as external warfare (Divale 1974;Ember and Ember 1971), long distance hunting (Perry 1989) and reliance on female subsistence (Scelza and Bliege Bird 2008). A number of recent case studies have pointed out that residence patterns among foragers are flexible, facultative and may vary across the life course (Blurton Jones et al 2005;Marlowe 2010). Several recent cross-cultural studies that synthesize much of the comparative data on hunter-gatherers have highlighted the importance of bilocal and multilocal residence (Alvarez 2004;Gray and Marlowe 2006;Kelly 1995;Marlowe 2004; see Table 1 for definition of italicized words). ...
... In small-scale populations with smaller or changing resident membership, preferred lineality would limit the number of potential collaborators whereas bilaterality is maximally inclusive of kin (Alvard 2002;Ember 1975). This one reason why the characterization of hunter-gatherers as predominantly patrilineal or matrilineal has been challenged (Blurton Jones et al 2005;Hiatt 1962;Lee 1972Lee , 1979Marlowe 2004Marlowe , 2010Szcela and Bliege Bird 2008;Turnbull 1965;Woodburn 1972). ...
Dispersal of individuals from their natal communities at sexual maturity is an important determinant of kin association. In this paper we compare postmarital residence patterns among Pumé foragers of Venezuela to investigate the prevalence of sex-biased vs. bilateral residence. This study complements cross-cultural overviews by examining postmarital kin association in relation to individual, longitudinal data on residence within a forager society. Based on cultural norms, the Pumé have been characterized as matrilocal. Analysis of Pumé marriages over a 25-year period finds a predominant pattern of natalocal residence. We emphasize that natalocality, bilocality, and multilocality accomplish similar ends in maximizing bilateral kin affiliations in contrast to sex-biased residential patterns. Bilateral kin association may be especially important in foraging economies where subsistence activities change throughout the year and large kin networks permit greater potential flexibility in residential mobility.
... These data are based on a society's marriage rules and postmarital residence norms, which do not account for individual patterning or lifetime variation (reviewed in [68]). The preponderance of patrilocality is challenged by studies using high-quality, longitudinal and individual-level residential data, which show that hunter-gatherer residence is fluid, facultative and changes frequently across the life course (also called bilocal or mulitlocal residence) [57,[69][70][71][72][73]. Spouses often move between local groups, shifting affiliation between maternal and paternal kin. ...
Women and girls cooperate with each other across many domains and at many scales. However, much of this information is buried in the ethnographic record and has been overlooked in theoretic constructions of the evolution of human sociality and cooperation. The assumed primacy of male bonding, hunting, patrilocality and philopatry has dominated the discussion of cooperation without balanced consideration. A closer look at the ethnographic record reveals that in addition to cooperative childcare and food production, women and girls collectively form coalitions, have their own cooperative political, ceremonial, economic and social institutions, and develop female-based exchange and support networks. The numerous ethnographic examples of female cooperation urge reconsideration of gender stereotypes and the limits of female cooperation. This review brings together theoretic, cross-cultural and cross-lifespan research on female cooperation to present a more even and empirically supported view of female sociality. Following the lead from trends in evolutionary biology and sexual selection theory, the hope going forward is that the focus shifts from rote characterizations of sex differences to highlighting sources of variation and conditions that enhance or constrain female cooperative engagement.
This article is part of the theme issue ‘Cooperation among women: evolutionary and cross-cultural perspectives’.
... Moreover, I contended that these cooperative preferences may have disincentivized women's overt expressions of competitiveness, malice or aggression, perhaps favoring instead prosocial manifestations of intrasexual rivalry and self-deception. Rucas and Alami (2021) forwarded perhaps one of the most formidable critiques to my arguments, contending that ancestral women may have less often found themselves alienated from kin either because patrilocality was not universally practiced, because mothers often resided with adult daughters (Blurton Jones et al., 2005), because men often engaged in brideservice (Daly & Wilson, 1983;Walker et al., 2011), or because women traveled to visit their mothers (Alvarez, 2004). Indeed, in support of their contentions, an analysis of 32 hunter gatherer societies found support for bisexual philopatry/dispersal and that co-residence with adult siblings was common . ...
Hunter-gatherer (aka forager) child-rearing has been frequently depicted as highly cooperative, with infants and children receiving care from many individuals, including parents and extensive alloparental networks. Although considerable research has been conducted exemplifying these patterns among hunter-gatherers, stepfamilies have rarely been addressed in these studies. Among Central African foragers, including the Bofi foragers, divorce and remarriage are common and cooperative care and alloparental involvement is pervasive. In the current study, the caregiving experiences of Bofi forager young children (ages one to four years) are examined in relation to living in a family with a stepfather or their biological father. Children’s interactions with and caregiving received from parents and alloparents are described and compared across family type to identify key differences and similarities between the two contexts. Larger community demographic patterns among the Bofi foragers are also examined to understand the relative typicality of children of various ages living in a stepfamily. Implications for research and theory related to cooperative care and the complementary care patterns of grandmothers and stepfathers are discussed.
As source, sustainer, and restorer of life, water has been an indispensable resource in hominin evolution. The water traditions of all people are based on the sources of water in their environment and the ways in which they access, manage, and make use of it in all aspects of their way of life. Because most of hominin history has been based on hunting and gathering, it is important to understand the water traditions of this particular mode of adaptation, especially in relation to the ethnography of historical and contemporary foragers in arid tropical environments. Some have argued that anthropologists have taken for granted the importance of water in human life, but water is too important a feature of the planetary surface and of terrestrial environments – and of any environment considered habitable by human beings – to have been passed over by anthropologists.
Humans belong to the few species in which females and males live for a relatively
long time after the end of their reproductive period. In this paper, I present theoretical
concepts explaining the relatively long post-reproductive life span of humans and
the menopause: the grandmother hypothesis and the diet, intelligence and longevity
model (also known as the embodied capital model). The grandmother hypothesis,
offering an evolutionary explanation of the menopause, shows that throughout most
of the human history, childrearing has been a cooperative endeavour. In all societies
across the world, mothers, fathers, grandparents, and other family members cooperate
in networks consisting of kins and non-kins in order to assist with child rearing.
The paper also argues how ethnographic research can contribute to the testing of
evolutionary theories of grandparenthood in contemporary societies.
Risk is inevitable, and managing it is an important component of individual and community strategies to adapt to local conditions. In this chapter we provide an overview of the risk management frameworks in eight communities to show how each society manages risk socially. We focus especially on the use of need-based transfers to buffer the effects of disasters and ecological uncertainty and provide abundant evidence that need-based transfers are a common strategy for the social management of risk. We use the terms need-based transfers and debt-based transfers rather than other existing terms because no current terms used in the literature capture the underlying logic of need-based transfers. They do not describe the kinds of formal, contractual risk-pooling arrangements found at some of our field sites. The Human Generosity Project, a transdisciplinary effort to examine both biological and cultural influences on human cooperation, has documented and analyzed these and many other examples of social risk management.
Small populations are susceptible to high genetic loads and random fluctuations in birth and death rates. While these selective forces can adversely affect their viability, small populations persist across taxa. Here, we investigate the resilience of small groups to demographic uncertainty, and specifically to fluctuations in adult sex ratio (ASR), partner availability and dispersal patterns. Using 25 years of demographic data for two Savannah Pumé groups of South American hunter–gatherers, we show that in small human populations: (i) ASRs fluctuate substantially from year to year, but do not consistently trend in a sex-biased direction; (ii) the primary driver of local variation in partner availability is stochasticity in the sex ratio at maturity; and (iii) dispersal outside of the group is an important behavioural means to mediate locally constrained mating options. To then simulate conditions under which dispersal outside of the local group may have evolved, we develop two mathematical models. Model results predict that if the ASR is biased, the globally rarer sex should disperse. The model’s utility is then evaluated by applying our empirical data to this central prediction. The results are consistent with the observed hunter–gatherer pattern of variation in the sex that disperses. Together, these findings offer an alternative explanation to resource provisioning for the evolution of traits central to human sociality (e.g. flexible dispersal, bilocal post-marital residence and cooperation across local groups). We argue that in small populations, looking outside of one’s local group is necessary to find a mate and that, motivated by ASR imbalance, the alliances formed to facilitate the movement of partners are an important foundation for the human-typical pattern of network formation across local groups. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
Our species’ biological success is unsurpassed – an achievement largely accredited to our remarkable capacity to cooperate. Large-scale cooperation, however, remains a puzzle. Recent work suggests that belief in the existence of omnipresent and omnipotent moralistic deities may have contributed to the emergence and maintenance of cooperation in large-scale societies. This study examines the relationship between religiosity and cooperation in the Hadza, one of the few remaining hunter-gatherer populations in the world. Hadza were surveyed about their religious beliefs and participated in two incentivized economic games, designed to measure rule-bending in favor of one’s campmates (game 1) and self (game 2) at the expense of Hadza living in other camps. Consistent with previous ethnographic descriptions, the Hadza engage in few religious practices and lack a strong belief in the existence of powerful and moralizing deities. The Hadza also show very high levels of rule-bending. There is, however, little evidence that belief in moralistic deities is associated with decreased rule-bending within the Hadza. Instead, the findings suggest that rule-bending for one’s campmates increases as the proportion of kin in one’s camp increases. Also, Hadza living in a geographic region close to markets and increased tourism exhibit greater rule-bending in favor of self compared to more isolated Hadza. The high levels of rule-bending and low levels of religiosity observed in the Hadza are discussed in light of the strong norms of sharing and egalitarianism that characterize their lives.
Food preferences are important for understanding foraging choices. In studying human foragers rather than other animals, we have the advantage of being able to ask them which foods they prefer. Yet surprisingly, no studies of systematically collected data exist on human forager food preferences. The Hadza of Tanzania are full-time foragers in an area where the hominin record extends back to 3-4 million years ago, so their diet is very relevant for understanding the paleo-diet. Here, we report on their food preferences, elicited with photographs of species within the five major food categories in their diet: honey, meat, berries, baobab, and tubers. There were sex differences in the ranks of two food categories: meat and berries. While male and female ranks agreed on the other three food categories, females ranked berries second and meat fourth, whereas males ranked meat second and berries fourth. Theses similarities and differences are interesting in light of the fact that the sexes target different foods. We discuss the implications of Hadza food preferences for the origin of the uniquely human sexual division of foraging labor.
Among hunter-gatherers, the sharing of male and female foods is often assumed to result in virtually the same diet for males and females. Although food sharing is widespread among the hunting and gathering Hadza of Tanzania, women were observed eating significantly more tubers than men. This study investigates the relationship between patterns of dental wear, diet, and extramasticatory use of teeth among the Hadza. Casts of the upper dentitions were made from molds taken from 126 adults and scored according to the Murphy dental attrition scoring system. Females had significantly greater anterior occlusal wear than males when we controlled for age. Males exhibited greater asymmetry in wear, with greater wear on the left side in canines, first premolars, and first molars. We suggest that these sex differences in wear patterns reflect the differences seen in the diet, as well as in the use of teeth as tools.
Cooperative child care among humans, where individuals other than the biological mother (allomothers) provide care, may increase
a mother’s fertility and the survivorship of her children. Although the potential benefits to the mother are clear, the motivations
for allomothers to provide care are less clear. Here, we evaluate the kin selection allomothering hypothesis using observations
on Hadza hunter-gatherers collected in ten camps over 17months. Our results indicate that related allomothers spend the largest
percentage of time holding children. The higher the degree of relatedness among kin, the more time they spend holding, supporting
the hypothesis of nepotism as the strongest motivation for providing allomaternal care. Unrelated helpers of all ages also
provide a substantial amount of investment, which may be motivated by learning to mother, reciprocity, or coercion.
When we have asked Hadza whether married couples should live with the family of the wife (uxorilocally) or the family of the husband (virilocally), we are often told that young couples should spend the first years of a marriage living with the wife's family, and then later, after a few children have been born, the couple has more freedom--they can continue to reside with the wife's kin, or else they could join the husband's kin, or perhaps live in a camp where there are no close kin. In this paper, we address why shifts in kin coresidence patterns may arise in the later years of a marriage, after the birth of children. To do so, we model the inclusive fitness costs that wives might experience from leaving their own kin and joining their husband's kin as a function of the number of children in their nuclear family. Our model suggests that such shifts should become less costly to wives as their families grow. This simple model may help explain some of the dynamics of postmarital residence among the Hadza and offer insight into the dynamics of multilocal residence, the most prevalent form of postmarital residence among foragers.
ResearchGate has not been able to resolve any references for this publication.