Female-biased parental investment is unusual but not unknown in human societies. Relevant explanatory models include Fisher’s principle, the Trivers-Willard model, local mate and resource competition and enhancement, and economic rational actor models. Possible evidence of female-biased parental investment includes sex ratios, mortality rates, parents’ stated preferences for offspring of one sex, and direct and indirect measurements of actual parental behavior. Possible examples of female-biased parental investment include the Mukogodo of Kenya, the Ifalukese of Micronesia, the Cheyenne of North America, the (...) Herero of southern Africa, the Kanjar of south Asia, the Mundugumor of New Guinea, contemporary North America, and historical Germany, Portugal, and the United States. (shrink)

To explain social learning without invoking the cognitively complex concept of imitation, many learning mechanisms have been proposed. Borrowing an idea used routinely in cognitive psychology, we argue that most of these alternatives can be subsumed under a single process, priming, in which input increases the activation of stored internal representations. Imitation itself has generally been seen as a This has diverted much research towards the all-or-none question of whether an animal can imitate, with disappointingly inconclusive results. In the great (...) apes, however, voluntary, learned behaviour is organized hierarchically. This means that imitation can occur at various levels, of which we single out two clearly distinct ones: the a rather detailed and linear specification of sequential acts, and the a broader description of subroutine structure and the hierarchical layout of a behavioural Program level imitation is a high-level, constructive mechanism, adapted for the efficient learning of complex skills and thus not evident in the simple manipulations used to test for imitation in the laboratory. As examples, we describe the food-preparation techniques of wild mountain gorillas and the imitative behaviour of orangutans undergoing to the wild. Representing and manipulating relations between objects seems to be one basic building block in their hierarchical programs. There is evidence that great apes suffer from a stricter capacity limit than humans in the hierarchical depth of planning. We re-interpret some chimpanzee behaviour previously described as and suggest that all great apes may be able to imitate at the program level. Action level imitation is seldom observed in great ape skill learning, and may have a largely social role, even in humans. (shrink)

Ethnic nepotism theory predicts that even in times of communal peace altruism is more pronounced within than between ethnic groups. The present study tested the hypothesis that altruism in the form of alms giving would be greater within than between ethnic groups, and greater between more closely related groups than between more distant groups. The three groups chosen for study were ethnic Russians, Moldavians, and Gypsies. Russians are genetically closer to Moldavians than to Gypsies. Observations were made of 128 ethnic (...) Russian, 25 Moldavian, and 25 Gypsy beggars receiving gifts from ethnic Russians in Moscow trains. The Gypsies were mainly girls, contrary to the Russian sample. Multivariate analysis identified three main strategies: active, personified, and appeasing-undirected. Russian strategies were most variable. Gypsies presented strong charity releasers: 84% were children who played music and sang and showed appeasing-undirected behavior. The few adults were highly submissive or friendly. Nevertheless, their success was limited compared with that of ethnic Russians despite the latter’s demanding behavior and their being mostly mature or elderly persons. Moldavians received an intermediate amount of charity. The hypothesis was supported. (shrink)

This paper provides a roadmap for engaging in cross-cultural, developmental research in practical, ethical, and community-engaged ways. To cultivate the flexibility necessary for conducting cross-cultural research, we structure our roadmap as a series of questions that each research program might consider prior to embarking on cross-cultural examinations in developmental science. Within each topic, we focus on the challenges and opportunities inherent to different types of study designs, fieldwork, and collaborations because our collective experience in conducting research in multiple cultural contexts (...) has taught us that there can be no single “best practice”. Here we identify the challenges that are unique to cross-cultural research as well as present a series of recommendations and guidelines. We also bring to the forefront ethical considerations which are rarely encountered in the laboratory context, but which researchers face daily while conducting research in a cultural context which one is not a member. As each research context requires unique solutions to these recurring challenges, we urge researchers to use this set of questions as a starting point, and to expand and tailor the questions and potential solutions with community members to support their own research design or cultural context. This will allow us to move the field towards more inclusive and ethical research practices. (shrink)

The significance of teaching to the evolution of human culture is under debate. We contribute to the discussion by using a quantitative, cross-cultural comparative approach to investigate the role of teaching in the lives of children in two small-scale societies: Aka foragers and Ngandu farmers of the Central African Republic. Focal follows with behavior coding were used to record social learning experiences of children aged 4 to 16 during daily life. “Teaching” was coded based on a functional definition from evolutionary (...) biology. Frequencies, contexts, and subtypes of teaching as well as the identity of teachers were analyzed. Teaching was rare compared to observational learning, although both forms of social learning were negatively correlated with age. Children received teaching from a variety of individuals, and they also engaged in teaching. Several teaching types were observed, including instruction, negative feedback, and commands. Statistical differences in the distribution of teaching types and the identity of teachers corresponded with contrasting forager vs. farmer foundational cultural schema. For example, Aka children received less instruction, which empirically limits autonomous learning, and were as likely to receive instruction and negative feedback from other children as they were from adults. Commands, however, exhibited a different pattern suggesting a more complex role for this teaching type. Although consistent with claims that teaching is relatively rare in small-scale societies, this evidence supports the conclusion that teaching is a universal, early emerging cognitive ability in humans. However, culture structures the nature of teaching. (shrink)

The Darwinian theory of evolution is itself evolving and this book presents the details of the core of modern Darwinism and its latest developmental directions. The authors present current scientific work addressing theoretical problems and challenges in four sections, beginning with the concepts of evolution theory, its processes of variation, heredity, selection, adaptation and function, and its patterns of character, species, descent and life. The second part of this book scrutinizes Darwinism in the philosophy of science and its usefulness in (...) understanding ecosystems, whilst the third section deals with its application in disciplines beyond the biological sciences, including evolutionary psychology and evolutionary economics, Darwinian morality and phylolinguistics. The final section addresses anti-Darwinism, the creationist view and issues around teaching evolution in secondary schools. The reader learns how current experimental biology is opening important perspectives on the sources of variation, and thus of the very power of natural selection. This work examines numerous examples of the extension of the principle of natural selection and provides the opportunity to critically reflect on a rich theory, on the methodological rigour that presides in its extensions and exportations, and on the necessity to measure its advantages and also its limits. Scholars interested in modern Darwinism and scientific research, its concepts, research programs and controversies will find this book an excellent read, and those considering how Darwinism might evolve, how it can apply to the human sciences and other disciplines beyond its origins will find it particularly valuable. Originally produced in French (Les Mondes Darwiniens), the scope and usefulness of the book have led to the production of this English text, to reach a wider audience. This book is a milestone in the impressive penetration by Francophone scholars into the world of Darwinian science, its historiography and philosophy over the last two decades. Alex Rosenberg, R. Taylor Cole Professor of Philosophy, Duke University Until now this useful and comprehensive handbook has only been available to francophones. Thanks to this invaluable new translation, this collection of insightful and original essays can reach the global audience it deserves. Tim Lewens, University of Cambridge. (shrink)

Research on human-animal interaction has skyrocketed in the last decade. Rapid urbanization has led scientists to investigate its impact on several species living in the vicinity of humans. Domesticated dogs (Canis lupus familiaris) are one such species that interact with humans and are also called man’s best friend. However, when it comes to the free-ranging population of dogs, interactions become quite complicated. Unfortunately, studies regarding free-ranging dog-human interactions are limited even though the majority of the world’s dog population is free-ranging. (...) In this study, we observed twelve groups of free-ranging dogs in their natural habitat, the streets. We divided the study areas into two zones, namely – intermediate and high flux, based on human activity or movement. Six groups from each of the zones were observed mostly during daytime. We used social network analysis (SNA) to explore the dog-dog (intraspecific) and dog-human (interspecific) interactions. It was surprising to observe higher instances of interspecific interactions than the intraspecific ones, irrespective of the zones. Humans, in significantly higher occasions, initiated both positive and negative interactions in comparison to dogs. Our findings conclude that humans are a crucial part of the interaction network of Indian free-ranging dogs. (shrink)

The ideals and realities of field research have shaped the development of behavioural primatology over the latter half of the twentieth century. This paper draws on interviews with primatologists as well as a survey of the scientific literature to examine the idealized notion of the field site as a natural place and the physical environment of the field as a research space. It shows that what became standard field practice emerged in the course of wide ranging debate about the techniques, (...) personal qualities and site conditions best suited to the scientific study of the natural behaviour of apes and monkeys. Although the laboratory was a constant presence in this debate, the export of techniques from the laboratory to the field was limited, due to concerns that experimental manipulation would destroy the naturalness of the behaviour. The paper goes on to demonstrate the central significance given by primatologists to the unique social, historical and ecological circumstances of particular field sites, and to sketch some of the complexities that fieldworkers contend with in trying to realize their ideals. Primatologists seek field sites that answer their questions; but once their studies become long term, they also need to find questions that answer to ever changing conditions at those sites. (shrink)

Native peoples have often been portrayed as natural conservationists, living a “balanced” existence with nature. It is argued that this perspective is a result of an imprecise operational definition of conservation. Conservation is defined here in contrast to the predictions of foraging theory, which assumes that foragers will behave to maximize their short-term harvesting rate. A behavior is deemed conservation when a short-term cost is paid by the resource harvester in exchange for long-term benefits in the form of sustainable harvests. (...) An example of the usefulness of such an operational definition is presented using data on patch and prey choice decisions of a group of subsistence hunters, the Piro of Amazonian Peru. Results indicate that the area around the Piro village is depleted of prey, and that hunters allocate more time to patches where return rates are highest. This response is consistent with both a conservation strategy and foraging theory. Contrary to the expectation of the conservation strategy, however, hunters do not restrain from pursing opportunistically encountered prey in the depleted areas. The implications for conservation policy are briefly discussed. (shrink)

Culturally inherited institutional norms structure much of human social life. Successfully replicating institutions train their current members to behave in the generally adaptive ways that served past members. Ancestor veneration is a well-known manifestation of this phenomenon whereby deference is conferred to prestigious past members who are used as cultural models. Such norms of respect may be maintained by punishment based on evidence from theory and laboratory experiments, but there is little observational evidence to show that punishment is commonly used. (...) To test for punishment as a mechanism that maintains these norms, we examine a norm of ancestor veneration in a natural field experiment at the Memorial Student Center at Texas A&M University. The MSC is a memorial to university war dead, and the expectation is that all who enter the building remove their hats out of respect. Observations reveal that hat removal is significantly more common at the MSC than at two control locations. Survey data indicate that most, but not all, subjects understand the norm to be veneration of the dead, and most expect others to follow the norm. Many report a strong negative emotional response when asked to imagine the norm being violated. Sixty-two percent report they would definitely or probably ask the noncompliant to uncover. Focal follow data show that punishment is relatively rare, however, with the majority of behatted subjects going unreproached as they pass through the building. Both survey and observational data indicate there is a motivated minority that enthusiastically enforces the norm. (shrink)

Research on brain or cognitive/affective processes, culture, social interaction, and structural analysis are overlapping but often independent ways humans have attempted to understand the origins of their evolution, historical, and contemporary development. Each level seeks to employ its own theoretical concepts and methods for depicting human nature and categorizing objects and events in the world, and often relies on different sources of evidence to support theoretical claims. Each level makes reference to different temporal bandwidths (milliseconds, seconds, minutes, hours, days, months, (...) years, decades, and centuries) and focuses on different spatio-temporal activities and controlled and non-controlled stimulus conditions. Biological mechanisms and environmental pressures for survival simultaneously created a gradual intersection and enhancement of cognitive/affective skills, cultural practices, and changes in collaborative social interaction and communicative skills. The evolution of a given level of analysis is assumed to have been incremental and overlapping. These innovative and independent ways humans have learned to characterize their brain or cognitive/affective and social/economic/political life often depend on unexamined, representational re-descriptions or cognitive/affective and socio-cultural devices and forms of communication that facilitate the depiction of practices and beliefs we attribute to respondents or subjects and research colleagues. (shrink)

Feminist philosophers of biology bring the tools of feminist theory, and in particular the tools of feminist philosophy of science, to investigations of the life sciences. While the critical examination of the categories of sex and gender (which will be explained below) takes a central place, the methods, ontological assumptions, and foundational concepts of biology more generally have also enjoyed considerable feminist scrutiny. Through such investigations, feminist philosophers of biology reveal the extent to which the theory and practice of particular (...) scientific disciplines and research programs (and, indeed, their philosophical study) are intertwined with both value judgments and social hierarchies. (shrink)

The two main theories of food-associated calls in animals propose functions either in cooperative recruitment or competitive spacing. However, not all social animals produce food calls and it is largely unclear under what circumstances this call type evolves. Sooty mangabeys do not have food calls, but they frequently produce grunts during foraging, their most common vocalisation. We found that grunt rates were significantly higher when subjects were foraging in the group’s periphery and with small audiences, in line with the cooperative (...) recruitment hypothesis. In a subsequent field experiment we presented highly desired food items and found that discovering individuals called, unless harassed by competitors, but that the calls never attracted others, confirming that the grunts do not convey any information referential to food. Our data thus suggest that the evolution of cooperative food calling is a two-step process, starting with increased motivation to vocalise in the feeding context, followed by the evolution of acoustic variants derived from context-general contact calls. This evolutionary transition may only occur in species that feed on clumped, high-quality resources where social feeding is competitive, a condition not met in sooty mangabeys. (shrink)

Drawing on ethnographic, ethological, and historical data, we examined the relationships between orangutans and caregivers at Auckland Zoo. Caregivers displayed high levels of empathy and adjusted their husbandry routines to their interpretations of the orangutans’ moods. Caregivers experienced conflicts arising from their efforts to empathize. Although they agreed their husbandry approach improved welfare, they worried their interpretations of orangutan behavior were inaccurate anthropomorphic projections. However, caregivers’ interpretations aligned well with ethological observations and with current knowledge of orangutan behavior. Caregivers’ shared (...) view of great apes as moral persons led to personal conflicts about the ethics of sacrificing individual orangutans’ freedom for the greater good of the species. By exploring caregivers’ personal conflicts, we aimed to inform debates about the politics of empathizing with animals, the role of zoos, and the ethics of keeping great apes in captivity. We argue the use of empathy is essential for engaging in intersubjective relationships. (shrink)

Contrary to spontaneous yawning, which is widespread in vertebrates and probably evolutionary ancient, contagious yawning—yawning triggered by others’ yawns—is considered an evolutionarily recent phenomenon, found in species characterized by complex sociality. Whether the social asymmetry observed in the occurrence of contagious yawning is related to social and emotional attachment and may therefore reflect emotional contagion is a subject of debate. In this study we assessed whether yawn contagion was enhanced in pregnant women, a cohort of subjects who develop prenatal emotional (...) attachment in preparation for parental care, via hormonal and neurobiological changes. We predicted that if yawn contagion underlies social and emotional attachment, pregnant women would be more likely to contagiously yawn than nonpregnant, nulliparous women of reproductive age. We gathered data in two different settings. In the experimental setting, 49 women were exposed to video stimuli of newborns either yawning or moving their mouth and we video-recorded the women during repeated trials to measure their yawning response. In the naturalistic setting, 131 women were observed in a social environment and their yawning response was recorded. We tested the factors influencing the yawning response, including the reproductive status. In both settings, yawn contagion occurred significantly more in pregnant than nonpregnant women. By showing that pregnant women were most likely to respond to others’ yawns, our results support the hypothesis that the social variation observed in yawn contagion may be influenced by emotional attachment and that yawning in highly social species might have been coopted for emotional contagion during evolution. (shrink)

Honest signalling theory suggests that humans and chimpanzees can extract socially relevant information relating to personality from the faces of their conspecifics. Humans are also able to extract information from chimpanzees’ faces. Here, we examine whether personality characteristics of chimpanzees, including measures of psychopathy, can be discerned based purely on facial morphology in photographs. Twenty-one chimpanzees were given naïve and expert personality ratings on the Ten Item Personality Inventory (TIPI) and the Chimpanzee Triarchic Model of Psychopathy (CHMP-Tri) before and following (...) behavioural observations. Characteristics relating to openness, conscientiousness, extraversion, and disinhibition could be distinguished from the faces of chimpanzees. Individuals higher on disinhibition have lower scores on conscientiousness and emotional stability and higher scores on extraversion, while those higher on meanness have lower conscientiousness and agreeableness. Facial expressions are linked to personality traits present in the TIPI and CHMP-Tri models: the Relaxed Face and the Grooming Face were displayed more by chimpanzees higher on agreeableness, whereas the Compressed Lips Face was observed more in those individuals higher on boldness, and the Full Open Grin was displayed more by chimpanzees higher on extraversion but lower on emotional stability and conscientiousness. Facial expressions were also found to be associated with particular behavioural contexts, namely the Grooming Face in affiliative contexts and the Relaxed and Relaxed Open Mouth Faces in neutral contexts. Dominant chimpanzees display higher levels of boldness and more Compressed Lips Faces, Relaxed Open Mouth Faces, and Grooming Faces than subordinate individuals. These findings support and extend evidence for an honest signalling system and a personality structure shared between humans and chimpanzees. Future research could further explore how personality is conveyed through the face, perhaps through more than just singular aspects of character, and maybe reflecting what chimpanzees themselves are able to do. (shrink)

Place, practice and status have played significant and interacting roles in the complex history of primatology during the early to mid-twentieth century. This paper demonstrates that, within the emerging discipline of primatology, the field was understood as an essential supplement to laboratory work. Founders argued that only in the field could primates be studied in interaction with their natural social group and environment. Such field studies of primate behavior required the development of existing and new field techniques. The practices and (...) sites developed by American primatologist Clarence Ray Carpenter were used to demonstrate that scientific standards could be successfully applied to the study of primates in the field. In an environment in which many field biologists fought for higher scientific status, Carpenter gradually adopted increasingly interventionist techniques. These techniques raised epistemological problems for studies whose value rested on the naturalness of the behaviors observed. Thus, issues of status shaped field practices and subsequently altered Carpenter's criteria for what constituted natural primate behavior. (shrink)

Place, practice and status have played significant and interacting roles in the complex history of primatology during the early to mid-twentieth century. This paper demonstrates that, within the emerging discipline of primatology, the field was understood as an essential supplement to laboratory work. Founders argued that only in the field could primates be studied in interaction with their natural social group and environment. Such field studies of primate behavior required the development of existing and new field techniques. The practices and (...) sites developed by American primatologist Clarence Ray Carpenter were used to demonstrate that scientific standards could be successfully applied to the study of primates in the field. In an environment in which many field biologists fought for higher scientific status, Carpenter gradually adopted increasingly interventionist techniques. These techniques raised epistemological problems for studies whose value rested on the naturalness of the behaviors observed. Thus, issues of status shaped field practices and subsequently altered Carpenter's criteria for what constituted natural primate behavior. (shrink)

Berichte zur Wissenschaftsgeschichte, Volume 45, Issue 1-2, Page 164-188, June 2022.

In this paper I examine the intracultural variability of parental and alloparental caregiving among the Aka foragers of the Central African Republic. It has been suggested that maternal kin offer higher frequencies of allocare than paternal kin and that maternal investment in infants will decrease when alloparental assistance is provided. Behavioral observations were conducted on 15 eight- to twelve-monthold infants. The practice of brideservice and the flexibility of Aka residence patterns offered a means to test the effect of maternal residence (...) on parental and alloparental investment. There was significant variation in the frequency of investment and who supplied care to infants depending on whether mothers resided with their kin or their husbands’ kin. However, in spite of the variation in allocare, when all categories of caregivers were examined collectively, infants received similar overall levels of care. (shrink)

In this paper I examine the intracultural variability of parental and alloparental caregiving among the Aka foragers of the Central African Republic. It has been suggested that maternal kin offer higher frequencies of allocare than paternal kin and that maternal investment in infants will decrease when alloparental assistance is provided. Behavioral observations were conducted on 15 eight- to twelve-monthold infants. The practice of brideservice and the flexibility of Aka residence patterns offered a means to test the effect of maternal residence (...) on parental and alloparental investment. There was significant variation in the frequency of investment and who supplied care to infants depending on whether mothers resided with their kin or their husbands’ kin. However, in spite of the variation in allocare, when all categories of caregivers were examined collectively, infants received similar overall levels of care. (shrink)

This paper examines maternal trade-offs between subsistence/economic activities and caregiving, and it explores the effect of allomaternal investment on maternal time allocation and child care. I examine how nonmaternal investment in two multiple caregiving populations may offset possible risk factors associated with reductions in maternal caregiving. Behavioral observations were conducted on 8- to 12-month-old infants and their caregivers among the Aka tropical forest foragers and Ngandu farmers of Central Africa. Analysis demonstrates that mothers face trade-offs between subsistence/economic activities and infant (...) care. Infants receive less investment when their mothers engage in subsistence/economic activities, indicating a potential risk to those infants. However, results indicate that allomothers target their assistance during times when mothers are engaged in work activities, partially offsetting potential risks associated with the maternal trade-off. The effects of intercultural variability on maternal time allocation and allomaternal investment are also explored as a means of examining the potential impact of their behaviors on infant care. (shrink)

Several studies have suggested a matrilateral bias in allomaternal (non-maternal) infant and child caregiving. The bias has been associated with the allomother’s certainty of genetic relatedness, where allomothers with high certainty of genetic relatedness will invest more in children because of potential fitness benefits. Using quantitative behavioral observations collected on Ngandu 8- to 12-month-old infants from the Central African Republic, I examine who is caring for infants and test whether certainty of genetic relatedness may influence investment by allomothers. Results indicate (...) a matrilateral bias in caregiving by extended kin members, but this does not affect the total level of care infants receive when fathers and siblings are included in the analysis. These results replicate a previous study done among an adjacent foraging population and emphasize the importance of examining children’s complete social environments when addressing caregiving and child development. (shrink)

This study investigated the use of mobile telephones by males and females in a public bar frequented by professional people. We found that, unlike women, men who possess mobile telephones more often publicly display them, and that these displays were related to the number of men in a social group, but not the number of women. This result was not due simply to a greater number of males who have telephones: we found an increase with male social group size in (...) the proportion of available telephones that were on display. Similarly, there was a positive relationship between the number of visible telephones and the ratio of males to females. Our results further show that the increased display of telephones in groups with more males is not due to the ostensive function of these devices (i.e., the making and receiving of calls), although single males tended to use their phones more. We interpret these results within the framework of male-male competition, with males in larger group sizes functioning in an increasingly competitive environment. This competitive environment is suggested to be akin to a lek mating system in which males aggregate and actively display their qualities to females who assess males on a number of dimensions. We suggest that mobile telephones might be used by males as an indicator of their status and wealth (sensu “cultural ornaments”). (shrink)

The gestural repertoire of captive gorillas contains the so-called “hand-on“ (or “pat-off“) gesture in which one animals puts its flat hand on top of another's head, which often leads to cessation of the receiver's previous activity. We investigate the origins of this gesture and developmental aspects of gesture creation. We further analyze gesture form and use in relation to the age of the sender with special consideration of the reaction of the receiver to better explain the function of the hand-on. (...) The focus of the study is to compare this gesture across different age groups in gorillas in regard to both production and reception and to get insights into possible origins of the gesture. (shrink)

Work-themed play may allow children to learn complex skills, and ethno-typical and gender-typical behaviors. Thus, play may have made important contributions to the evolution of childhood through the development of embodied capital. Using data from Aka foragers and Ngandu farmer children from the Central African Republic, we ask whether children perform ethno- and gender-typical play and work activities, and whether play prepares children for complex work. Focal follows of 50 Aka and 48 Ngandu children were conducted with the aim of (...) recording children’s participation in 12 categories of work and work-themed play. Using these data, we test a set of hypotheses regarding how age, gender, ethnicity, and task complexity influence children’s activities. As hypothesized, we find performance of work-themed play is negatively correlated with age. Contrary to our hypothesis, children do not play more than they work at complex tasks, but they work more than they play at simple ones. Gender and ethnicity are associated with play and work at culturally salient activities, despite availability of other-gender and other-ethnicity social partners. Our findings show that ethnic and gender biases are apparent in the play and work behavior of Aka and Ngandu children. Moreover, our results show that play helps both forager and farmer children learn complex skills, consistent with play having an adaptive learning function. (shrink)

Notable in cross-cultural comparisons is the variable span of time between when children become economically self-sufficient and when they initiate their own reproductive careers. That variation is of interest because it shapes the age range of children reliant on others for support and the age range of children available to help out, which in turn affects the competing demands on parents to support multiple dependents of different ages. The age at positive net production is used as a proxy to estimate (...) the close of juvenile economic dependence among a group of Maya subsistence agriculturalists. Maya children produce more than they consume by their early to mid teens but remain in their natal households for a number of years before leaving home and beginning families of their own. The Maya results contrast markedly with those from several groups of hunter-gatherers and horticulturalists for whom we have similar data. Even in the Maya case, where children are self-sufficient at a relatively young age, parents are unable to support their children without help from others. The production surplus of older children appears to help underwrite the cost of large Maya families and subsidize their parents’ continued reproduction. (shrink)

Attention has been given to cross-cultural differences in adolescent growth, but far less is known about developmental variability during juvenility (ages 3–10). Previous research among the Pumé, a group of South American foragers, found that girls achieve a greater proportion of their adult stature during juvenility compared with normative growth expectations. To explain rapid juvenile growth, in this paper we consider girls’ activity levels and energy expended in subsistence effort. Results show that Pumé girls spend far less time in subsistence (...) tasks in proportion to their body size compared with adults, and they have lower physical activity levels compared with many juveniles cross-culturally. Low activity levels help to explain where the extra energy comes from to support rapid growth in a challenging environment. We suggest that activity levels are important to account for the variation of resource and labor transfers in mediating energy availability. (shrink)

In the mid 1970s labor-saving technology was introduced into a Maya subsistence agricultural community that markedly increased the efficiency with which maize could be ground and water collected. This increased efficiency introduces a possible savings in the time that women allocate to work, which can be reapportioned to child care, food production, domestic work, or leisure. An earlier study suggested that this labor-saving technology had a positive effect in decreasing the age at which these Maya women begin their reproductive careers. (...) Although there is a statistical association between the age at which women bear their first child and the introduction of modern technology, this association does not demonstrate that the decline in age at first birth is causally related to the presence of technology. This paper pursues two objectives to evaluate this potential causal relationship in greater detail. First, a theory relating technological change to the initiation of a reproductive career is briefly developed in order to make qualitative predictions about behavioral changes as a response to changing technology. Second, these predictions are then tested against time allocation data recently collected in this same Maya community.We suggest that both of the conditions necessary to initiate reproduction—fecundity and access to mates—fundamentally depend on the amount of help that a girl provides to her family. Further, the help that a girl provides can be affected by technological changes. Analyses show that when modern technology is available, unmarried young women do not change the time allocated to domestic tasks and child care, and allocate more time to low-energy leisure activities. This lack of perceived benefit to working more and a potential concomitant shift towards a positive energy balance may in part explain why Maya women leave home and initiate reproduction at a younger age after labor-saving technology is introduced. (shrink)

Research in nonindustrial small-scale societies challenges the common perception that human childhood is universally characterized by a long period of intensive adult investment and dedicated instruction. Using return rate and time allocation data for the Savanna Pumé, a group of South American hunter-gatherers, age patterns in how children learn to become productive foragers and from whom they learn are observed across the transition from childhood to adolescence. Results show that Savanna Pumé children care for their siblings, are important economic contributors, (...) learn by doing rather than by instruction, and spend their time principally in the company of other children. This developmental experience contrasts with that of children in postindustrial societies, who are dependent on adults, often well past maturity; learn in formal settings; and spend much of their time in the company of adults. These differences raise questions about whether normative behaviors observed in postindustrial societies are representative of human children. This comparison also identifies the potential mismatch between hunter-gatherer and postindustrial societies in the extent to which children may be well adapted to learn from and teach each other. In particular, spending time in autonomous work and play groups develops the cooperation and coordination skills that are foundational to human subsistence and growing up to be socially and productively adept adults and parents. (shrink)