How Do Hunter-Gatherer Children Learn Subsistence Skills?

Hunting and gathering is, evolutionarily, the defining subsistence strategy of our species. Studying how children learn foraging skills can, therefore, provide us with key data to test theories about the evolution of human life history, cognition, and social behavior. Modern foragers, with their vast cultural and environmental diversity, have mostly been studied individually. However, cross-cultural studies allow us to extrapolate forager-wide trends in how, when, and from whom hunter-gatherer children learn their subsistence skills. We perform a meta-ethnography, which allows us to systematically extract, summarize, and compare both quantitative and qualitative literature. We found 58 publications focusing on learning subsistence skills. Learning begins early in infancy, when parents take children on foraging expeditions and give them toy versions of tools. In early and middle childhood, children transition into the multi-age playgroup, where they learn skills through play, observation, and participation. By the end of middle childhood, most children are proficient food collectors. However, it is not until adolescence that adults (not necessarily parents) begin directly teaching children complex skills such as hunting and complex tool manufacture. Adolescents seek to learn innovations from adults, but they themselves do not innovate. These findings support predictive models that find social learning should occur before individual learning. Furthermore, these results show that teaching does indeed exist in hunter-gatherer societies. And, finally, though children are competent foragers by late childhood, learning to extract more complex resources, such as hunting large game, takes a lifetime.     

Subsistence Farmers’ Management of Infestations of the Little Fire Ant in Garden Plots on Bauro,Makira Province,Solomon Islands

The little fire ant Wasmannia auropunctata is known to negatively impact the native fauna of tropical islands in the Pacific and its sting is a nuisance to farmers in their garden plots. We examine whether the presence of the little fire ant has the potential to disrupt subsistence gardening practices, with implications for livelihoods and wellbeing. We used structured questionnaires, analysed quantitatively, with 90 participants from the Central Bauro area, Makira, the Solomon Islands, and more detailed semi-structured interviews, analysed qualitatively, with another six people. Our results show that the presence of the little fire ant affects gardening activities by reducing time spent working effectively, influencing decisions about where to make gardening plots, discouraging children’s participation, and changing traditional gardening practices. We also find that the longer the ant is present, the more tolerant Central Bauro subsistence farmers become of its presence.     

Social learning across the life cycle: cultural knowledge acquisition for honey collection among the Jenu Kuruba,India

Accounting for age-dependent patterns of knowledge transmission is critical for understanding cultural evolution in age-structured populations. Cultural evolution theory predicts which social learning biases we expect people to use, but much less often when—during a person's life cycle— different social learning biases will be used. By measuring knowledge and skill variation among age cohorts, it is possible to infer how people socially acquire different types of knowledge at different ages. We use this strategy among the Jenu Kuruba, a tribal community in South India. We document the accumulation of local knowledge required for collecting wild honey among 71 children and 125 adults from five communities. Combining quantitative measurements of knowledge with measures of four honey-collecting skills and self-reported data on learning age, we infer patterns of social learning across the lifecycle. We find that (1) most knowledge related to honey collecting is acquired by the early 20s, and later social learning mainly functions to update information; (2) the eldest cohort has the highest average explicit knowledge, although the most knowledgeable or skilled individuals do not always belong to the most elderly cohort; (3) length of learning can be affected by age-dependent trade-offs of costs and benefits to learners; and (4) children tend to learn from parents, but individuals use other demonstrators later in life. These results have implications for current models of cultural evolution.     

Teachers’ civic socialization practices and children’s civic engagement

We examined the degree to which civic learning activities and civic discussion in the classroom were associated with children’s civic engagement in the upper elementary grades. We also explored the types of civic activities used by teachers during middle childhood. Survey data were collected from 359 ethnically and economically diverse 4th–6th grade students (M age?=?10.56, 56% female), their parents, and teachers (n?=?20) from six public schools in Southern California. The results of path analyses showed that teachers’ greater use of civic learning activities was associated with higher levels of social responsibility to people and civic values in students. However, general civic discussion was not associated with any indicators of children’s civic engagement. Additionally, teachers reported using numerous types of civic activities, thus showing the diversity in “civic learning” across classrooms. Practical implications for elementary civic education are discussed.     

Cross-sectional growth of pastoralist Karimojong and Turkana children

In this study, we compare cross-sectional growth in two Nilotic pastoralist populations, the Turkana and Karimojong of northern East Africa. Until the middle of the 18th century, these two groups constituted one population, and their genetic affinities consequently are assumed to be strong. Known differences in their subsistence practices as well as their recent cultural history allow us to consider the genetic vs. environmental determinants of their growth patterns. Growth in stature of the two groups is remarkably similar, whereas the pattern of ponderal growth varies, particularly in infancy and adolescence. Both groups demonstrate the linear adult physique that is characteristic of savanna-dwelling peoples in East Africa, but the Karimojong are heavier and fatter after early childhood. Linearity of physique is related to narrow skeletal breadth, a trait that emerges early in childhood among the Karimojong and is strongly correlated with weight: this finding supports the climatic hypothesis of human body shape and size. Extreme leanness, determined from body mass index, is correlated with fat stores, which are only weakly correlated with weight, height, or skeletal breadth. Linearity of physique appears to have a substantial genetic component, whereas fatness is hypothesized to relate to differences in subsistence strategies and exposure to environmental and cultural stress.     

Acute skin sun damage in children and its consequences in adults

Children spend more time outdoors than adults and there is compelling evidence that childhood is a particularly vulnerable time for the photocarcinogenic effects of the sun. The negative effects of solar radiation are accumulated during the entire lifetime; however 80% of total lifetime sun exposure is taking place before the age of 18 years. Child skin is more sensitive than adult skin because natural defense mechanisms are not fully developed. A short exposure to midday sun will result in sunburns. Epidemiologic studies show a higher incidence of malignant melanoma in persons with a history of sunburns during childhood and adolescence. Sun exposure among infants and pre-school children is largely dependent on the discretion of adult care providers. Sun protective habits of mothers may predict the level of sun exposure in children. It is very important to transfer the knowledge and positive habits of proper sun protection to children. The purpose of sun-safety behavior is not to avoid outdoor activities, but rather to protect the skin from detrimental sun effects. Proper sun protection of children includes protection from excessive sun exposure, sunburns and other forms of skin damage caused by sun, which may lead to the future development of skin cancers. This paper reviews acute skin reactivity to sun in childhood and adolescence that causes damage in skin structure and function and produces undesirable chronic changes in adults.     

Exploitation of Encephalartos transvenosus outside and inside Mphaphuli Cycads Nature Reserve, Limpopo Province, South Africa

This study has investigated the use and threats of Encephalartos transvenosus outside and inside Mphaphuli Cycads Nature Reserve, Limpopo Province, South Africa. Data were collected from 2005 to 2006 through social and ecological surveys. Semi-structured interviews were conducted with a total of 40 people per household, sampled from four selected villages around the reserve. E. transvenosus is used for medicinal purposes, decorations, cultural activities and as food. Youth and adult persons harvest E. transvenosus for income generation, while children and aged people mainly use it for subsistence purposes. The survival of E. transvenosus in the wild is uncertain due to various threats, such as illegal collection, habitat destruction, fire and grazing. Some conservation measures are also discussed.     

Developmental changes in emotion recognition from full-light and point-light displays of body movement

To date, research on the development of emotion recognition has been dominated by studies on facial expression interpretation; very little is known about children's ability to recognize affective meaning from body movements. In the present study, we acquired simultaneous video and motion capture recordings of two actors portraying four basic emotions (Happiness Sadness, Fear and Anger). One hundred and seven primary and secondary school children (aged 4-17) and 14 adult volunteers participated in the study. Each participant viewed the full-light and point-light video clips and was asked to make a forced-choice as to which emotion was being portrayed. As a group, children performed worse than adults for both point-light and full-light conditions. Linear regression showed that both age and lighting condition were significant predictors of performance in children. Using piecewise regression, we found that a bilinear model with a steep improvement in performance until 8.5 years of age, followed by a much slower improvement rate through late childhood and adolescence best explained the data. These findings confirm that, like for facial expression, adolescents' recognition of basic emotions from body language is not fully mature and seems to follow a non-linear development. This is in line with observations of non-linear developmental trajectories for different aspects of human stimuli processing (voices and faces), perhaps suggesting a shift from one perceptual or cognitive strategy to another during adolescence. These results have important implications to understanding the maturation of social cognition.     

On the relationship between interindividual cultural transmission and population-level cultural diversity: a case study of weaving in Iranian tribal populations

It is often assumed that parent-to-child cultural transmission leads to similarities and differences among groups evolving through descent with modification (“phylogenesis”). Similarly, cultural transmission between peers, and between adults and children who are not their offspring, is widely believed to result in groups exchanging cultural traits (“ethnogenesis”). However, neither of these assumptions has been examined empirically. Here, we test them using ethnographic data on craft learning in Iranian tribal populations and the cladistic method of phylogenetic analysis. We find that parent-to-child transmission dominates learning during childhood, but the other two forms of interindividual transmission become more important in later periods. The latter do not, however, appear to have resulted in extensive exchange of cultural traits among tribes. Instead we find that most of the variation among the tribes' craft assemblages can be explained by descent with modification. This can be accounted for by the fact that weavers usually only share their knowledge with members of their own tribe and are prevented from interacting with women from other groups by social norms. These findings demonstrate that the relationship between processes of cultural evolution at the level of the individual and processes of cultural evolution at the level of the group is more complex than is usually acknowledged, and highlight the need for more integrated studies of the processes operating at both scales.     

Early anthropometric indices predict short stature and overweight status in a cohort of Peruvians in early adolescence

While childhood malnutrition is associated with increased morbidity and mortality, less well understood is how early childhood growth influences height and body composition later in life. We revisited 152 Peruvian children who participated in a birth cohort study between 1995 and 1998, and obtained anthropometric and bioimpedance measurements 11-14 years later. We used multivariable regression models to study the effects of childhood anthropometric indices on height and body composition in early adolescence. Each standard deviation decrease in length-for-age at birth was associated with a decrease in adolescent height-for-age of 0.7 SD in both boys and girls (all P < 0.001) and 9.7 greater odds of stunting (95% CI 3.3-28.6). Each SD decrease in length-for-age in the first 30 months of life was associated with a decrease in adolescent height-for-age of 0.4 in boys and 0.6 standard deviation in girls (all P < 0.001) and with 5.8 greater odds of stunting (95% CI 2.6-13.5). The effect of weight gain during early childhood on weight in early adolescence was more complex to understand. Weight-for-length at birth and rate of change in weight-for-length in early childhood were positively associated with age- and sex-adjusted body mass index and a greater risk of being overweight in early adolescence. Linear growth retardation in early childhood is a strong determinant of adolescent stature, indicating that, in developing countries, growth failure in height during early childhood persists through early adolescence. Interventions addressing linear growth retardation in childhood are likely to improve adolescent stature and related-health outcomes in adulthood.     

Modeling Social Transmission Dynamics of Unhealthy Behaviors for Evaluating Prevention and Treatment Interventions on Childhood Obesity

Research evidence indicates that obesity has spread through social networks, but lever points for interventions based on overlapping networks are not well studied. The objective of our research was to construct and parameterize a system dynamics model of the social transmission of behaviors through adult and youth influence in order to explore hypotheses and identify plausible lever points for future childhood obesity intervention research. Our objectives were: (1) to assess the sensitivity of childhood overweight and obesity prevalence to peer and adult social transmission rates, and (2) to test the effect of combinations of prevention and treatment interventions on the prevalence of childhood overweight and obesity. To address the first objective, we conducted two-way sensitivity analyses of adult-to-child and child-to-child social transmission in relation to childhood overweight and obesity prevalence. For the second objective, alternative combinations of prevention and treatment interventions were tested by varying model parameters of social transmission and weight loss behavior rates. Our results indicated child overweight and obesity prevalence might be slightly more sensitive to the same relative change in the adult-to-child compared to the child-to-child social transmission rate. In our simulations, alternatives with treatment alone, compared to prevention alone, reduced the prevalence of childhood overweight and obesity more after 10 years (1.2–1.8% and 0.2–1.0% greater reduction when targeted at children and adults respectively). Also, as the impact of adult interventions on children was increased, the rank of six alternatives that included adults became better (i.e., resulting in lower 10 year childhood overweight and obesity prevalence) than alternatives that only involved children. The findings imply that social transmission dynamics should be considered when designing both prevention and treatment intervention approaches. Finally, targeting adults may be more efficient, and research should strengthen and expand adult-focused interventions that have a high residual impact on children.     

Context-dependent model-based biases in cultural transmission: children's imitation is affected by model age over model knowledge state

Many animals, including humans, acquire information through social learning. Although such information can be acquired easily, its potential unreliability means it should not be used indiscriminately. Cultural ‘transmission biases’ may allow individuals to weigh their reliance on social information according to a model's characteristics. In one of the first studies to juxtapose two model-based biases, we investigated whether the age and knowledge state of a model affected the fidelity of children's copying. Eighty-five 5-year-old children watched a video demonstration of either an adult or child, who had professed either knowledge or ignorance regarding a tool-use task, extracting a reward from that task using both causally relevant and irrelevant actions. Relevant actions were imitated faithfully by children regardless of the model's characteristics, but children who observed an adult reproduced more irrelevant actions than those who observed a child. The professed knowledge state of the model showed a weaker effect on imitation of irrelevant actions. Overall, children favored the use of a ‘copy adults’ bias over a ‘copy task-knowledgeable individual’ bias, even though the latter could potentially have provided more reliable information. The use of such social learning strategies has significant implications for understanding the phenomenon of imitation of irrelevant actions (overimitation), instances of maladaptive information cascades, and cumulative culture.     

Nutritional influence on childhood development and genetic control of adolescent growth of Quechuas and Mestizos from the Peruvian Lowlands

The growth in height of 1,202 Quechua and Mestizo children aged 6 to 19 years of the province of Lamas in the Peruvian Eastern Lowlands was studied. As shown by evaluations of ABO, Rh systems, and skin reflectance measurements, the Quechuas are genetically different from the Mestizos. The heights of Quechuas and Mestizos were matched for nutritional status based on measurements of subcutaneous fat and body muscle. The study indicates that: (1) during childhood, Quechuas and Mestizos matched for the same nutritional status attain similar heights; (2) during adolescence (or after the age of 11 years), the Mestizos are significantly taller than the Quechuas of the same nutritional status; 3) during childhood, the relative difference in height between Quechuas and Mestizos matched for the same nutritional status is less than the difference between Quechuas (or Mestizos) of the same genetic composition characterized by good and poor nutritional status. These findings suggest that the influence of environmental factors, such as nutrition, have a greater influence in producing differences in body size during childhood than during adolescence. Conversely, the present findings support the hypothesis that the influence of genetic factors on body size are greater during adolescence than during childhood. However, comparison of adolescent samples of similar genetic composition (whether they be Quechuas or Mestizos), characterized by good and poor nutritional status, reveal large differences in height, suggesting that under conditions of malnutrition, the genetic control of growth is diminished.     

Developmental Differences in the Structure of Executive Function in Middle Childhood and Adolescence

Although it has been argued that the structure of executive function (EF) may change developmentally, there is little empirical research to examine this view in middle childhood and adolescence. The main objective of this study was to examine developmental changes in the component structure of EF in a large sample (N = 457) of 7–15 year olds. Participants completed batteries of tasks that measured three components of EF: updating working memory (UWM), inhibition, and shifting. Confirmatory factor analysis (CFA) was used to test five alternative models in 7–9 year olds, 10–12 year olds, and 13–15 year olds. The results of CFA showed that a single-factor EF model best explained EF performance in 7–9-year-old and 10–12-year-old groups, namely unitary EF, though this single factor explained different amounts of variance at these two ages. In contrast, a three-factor model that included UWM, inhibition, and shifting best accounted for the data from 13–15 year olds, namely diverse EF. In sum, during middle childhood, putative measures of UWM, inhibition, and shifting may rely on similar underlying cognitive processes. Importantly, our findings suggest that developmental dissociations in these three EF components do not emerge until children transition into adolescence. These findings provided empirical evidence for the development of EF structure which progressed from unity to diversity during middle childhood and adolescence.     

Human children rely more on social information than chimpanzees do

Human societies are characterized by more cultural diversity than chimpanzee communities. However, it is currently unclear what mechanism might be driving this difference. Because reliance on social information is a pivotal characteristic of culture, we investigated individual and social information reliance in children and chimpanzees. We repeatedly presented subjects with a reward-retrieval task on which they had collected conflicting individual and social information of equal accuracy in counterbalanced order. While both species relied mostly on their individual information, children but not chimpanzees searched for the reward at the socially demonstrated location more than at a random location. Moreover, only children used social information adaptively when individual knowledge on the location of the reward had not yet been obtained. Social information usage determines information transmission and in conjunction with mechanisms that create cultural variants, such as innovation, it facilitates diversity. Our results may help explain why humans are more culturally diversified than chimpanzees.     

Social learning among Congo Basin hunter-gatherers

This paper explores childhood social learning among Aka and Bofi hunter-gatherers in Central Africa. Existing literature suggests that hunter-gatherer social learning is primarily vertical (parent-to-child) and that teaching is rare. We use behavioural observations, open-ended and semi-structured interviews, and informal and anecdotal observations to examine the modes (e.g. vertical versus horizontal/oblique) and processes (e.g. teaching versus observation and imitation) of cultural transmission. Cultural and demographic contexts of social learning associated with the modes and processes of cultural transmission are described. Hunter-gatherer social learning occurred early, was relatively rapid, primarily vertical under age 5 and oblique and horizontal between the ages of 6 and 12. Pedagogy and other forms of teaching existed as early as 12 months of age, but were relatively infrequent by comparison to other processes of social learning such as observation and imitation.     

The effects of prenatal exposure to Ramadan on stature during childhood and adolescence: Evidence from the Indonesian Family Life Survey

Many pregnant Muslim women fast during the Muslim holy month of Ramadan. A number of studies have reported negative life outcomes in adulthood for children who were prenatally exposed to Ramadan. However, other studies document minimal to no impact on neonatal indicators. Using data from the Indonesian Family Life Survey consisting of 45,246 observations of 21,723 children born to 9771 mothers, we contribute to the current discussion on prenatal exposure to Ramadan by examining the effects on stature (height-for-age Z-scores, weight-for-age Z-scores, and body-mass-index-for-age Z-scores: HAZ, WAZ, and BAZ, respectively) from early childhood to late adolescence (0–19 years of age). We introduce an objective mother’s religiosity indicator to improve the intention-to-treat estimations. Children were classified into three groups based on their mother’s religion-religiosity: religious Muslims, less-religious Muslims, and non-Muslims. Using cluster-robust mother fixed-effects, we found negative effects on stature for children born to religious Muslim mothers. The effects were age-dependent and timing-sensitive. For example, children born to religious Muslim mothers were shorter in late adolescence (15–19 years of age) compared to their unexposed siblings if they were prenatally exposed in the first trimester of pregnancy (HAZ difference = −0.105 SD; p-val. <0.05). Interestingly, we found positive effects on stature for exposed less-religious Muslim children that peak in early adolescence (10–14 years of age) and negative effects on stature for exposed non-Muslim children that occur only in early childhood (0–4 years of age). We nuance our discussion of health and socioeconomic factors to explain these surprising results.     

Adrenarche and Middle Childhood

Middle childhood, the period from 6 to 12 years of age, is defined socially by increasing autonomy and emotional regulation, somatically by the development of anatomical structures for subsistence, and endocrinologically by adrenarche, the adrenal production of dehydroepiandrosterone (DHEA). Here I suggest that DHEA plays a key role in the coordinated development of the brain and body beginning with middle childhood, via energetic allocation. I argue that with adrenarche, increasing levels of circulating DHEA act to down-regulate the release of glucose into circulation and hence limit the supply of glucose which is needed by the brain for synaptogenesis. Furthermore, I suggest the antioxidant properties of DHEA may be important in maintaining synaptic plasticity throughout middle childhood within slow-developing areas of the cortex, including the insula, thamalus, and anterior cingulate cortex. In addition, DHEA may play a role in the development of body odor as a reliable social signal of behavioral changes associated with middle childhood.     

Developmental stage‐dependent influence of environmental factors on growth of rural Sundanese children in West Java,Indonesia

This study investigated the growth trajectories and the relative relevance levels of nutrition, disease, and hormonal status at various developmental stages among children in adverse environments to provide population‐based empirical evidence for the life history theory. Three years of longitudinal anthropometric data in 1‐year intervals were obtained from 418 boys and girls aged 0 to 12 years at recruitment. Following the final measurement, the main survey, which included blood and feces sampling, 3‐h interval food consumption recall surveys for energy and nutrient intakes and anthropometry, was performed. Blood and feces were used for detecting, respectively, anemia and hormonal (IGF‐I and IGFBP‐3) levels as well as intestinal helminthiasis (Ascaris, Trichuris, and hookworm). The major findings of this study are summarized as follows: 1) the growth velocity of the subject children lagged behind international standards during childhood and juvenility but caught up during early adolescence; 2) diseases, both intestinal helminths and anemia, had significant effects on growth in childhood but not at older ages; and 3) hormonal status significantly affected growth in the children, with its highest significance in early adolescence. A larger growth than international standards in early adolescence likely follows programmed hormonal mechanisms after the onset of puberty. The onset of puberty might be associated with adequate amounts of nutrient intake and be mediated by hormonal function, because the IGF‐IZ score was significantly correlated with energy and protein intakes at the transitional period from juvenility to adolescence, when puberty occurs. Am J Phys Anthropol 157:94–106, 2015. © 2015 Wiley Periodicals, Inc.     

Embedded in the land: Customary social relations and practices of resilience in an East Timorese community

Drawing on a case study of Cacavei, a rural subsistence community in Timor‐Leste, this article explores the mutually constitutive relationship between people and land within customary forms of society. Patterns of land use and connection to land are not simply reflective of genealogical modes of social organisation, but are also enabling of them. Particularly, the embedding of ancestors within the land offers a means of accessing kinship relationships beyond the genealogical present. Embeddedness provides a quality of embodiment that makes ancestors active participants in social life. Constituted in the relational nexus of people and land, forms of social organisation in Cacavei have a mutability which goes some way to explaining the community’s resilience in spite of forced displacement and cultural disruption during the period of Indonesian occupation. This mutability might be considered more broadly as a source of resilience for customary communities grappling with modernising processes of change.