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Storytelling is a human universal. From gathering around the camp-fire telling tales of ancestors to watching the latest television box-set, humans are inveterate producers and consumers of stories. Despite its ubiquity, little attention has been given to understanding the function and evolution of storytelling. Here we explore the impact of storytelling on hunter-gatherer cooperative behaviour and the individual-level fitness benefits to being a skilled storyteller. Stories told by the Agta, a Filipino hunter-gatherer population, convey messages relevant to coordinating behaviour in a foraging ecology, such as cooperation, sex equality and egalitarianism. These themes are present in narratives from other foraging societies. We also show that the presence of good storytellers is associated with increased cooperation. In return, skilled storytellers are preferred social partners and have greater reproductive success, providing a pathway by which group-beneficial behaviours, such as storytelling, can evolve via individual-level selection. We conclude that one of the adaptive functions of storytelling among hunter gatherers may be to organise cooperation. Storytelling entails costs in terms of time and effort, yet it is a ubiquitous feature of human society. Here, Smith et al. show benefits of storytelling in Agta hunter-gatherer communities, as storytellers have higher reproductive success and storytelling is associated with higher cooperation in the group.

Contemporary hunter-gatherers are highly active, but little is known about physical activity levels in hunter-gatherer children. We analysed 150 days of accelerometer data from 51 BaYaka hunter-gatherer children (aged 3–18) in the Republic of Congo, comparing it with British and American children using samples from Millennium Cohort Study (MCS) and National Health and Nutrition Examination Survey (NHANES). BaYaka children were highly active, engaging in over 3 h of moderate-to-vigorous physical activity (MVPA) daily, surpassing British adolescents by over 70 min. Unlike US children, whose activity diminished with age, BaYaka children’s activity levels increased, irrespective of gender. This trend suggests that formal education may suppress activity among American children, a pattern not seen in the BaYaka community. Reflecting their foraging lifestyle, activity patterns varied within and between days in BaYaka children, a contrast to the more uniform daily activity observed in American children. Furthermore, our data challenges the concept of ‘teenage chronotypes’ prevalent in post-industrial societies, with adolescent BaYaka maintaining shorter sleep phases and later bedtimes, synchronized with sunrise. These findings highlight the impact of a foraging upbringing on children’s activity levels, providing a benchmark for understanding childhood physical activity and wellbeing.

Non-maternal carers (allomothers) are hypothesized to lighten the mother's workload, allowing for the specialized human life history including relatively short interbirth intervals and multiple dependent offspring. Here, using in-depth observational data on childcare provided to 78 Agta children (a foraging population in the northern Philippines; aged 0–6 years), we explore whether allomaternal childcare substitutes and decreases maternal childcare. We found that allomother caregiving was associated with reduced maternal childcare, but the substitutive effect varied depending on the source and type of care. Children-only playgroups consistently predicted a decrease in maternal childcare. While grandmothers were rarely available, their presence was negatively associated with maternal presence and childcare, and grandmothers performed similar childcare activities to mothers. These results underscore the importance of allomothering in reducing maternal childcare in the Agta. Our findings suggest that flexibility in childcare sources, including children-only playgroups, may have been the key to human life-history evolution. Overall, our results reinforce the necessity of a broad conceptualization of social support in human childcare. This article is part of the theme issue 'Multidisciplinary perspectives on social support and maternal–child health'.

High-fidelity transmission of information through imitation and teaching has been proposed as necessary for cumulative cultural evolution. Yet, it is unclear when and for which knowledge domains children employ different social learning processes. This paper explores the development of social learning processes and play in BaYaka hunter-gatherer children by analysing video recordings and time budgets of children from early infancy to adolescence. From infancy to early childhood, hunter-gatherer children learn mainly by imitating and observing others’ activities. From early childhood, learning occurs mainly in playgroups and through practice. Throughout childhood boys engage in play more often than girls whereas girls start foraging wild plants from early childhood and spend more time in domestic activities and childcare. Sex differences in play reflect the emergence of sexual division of labour and the play-work transition occurring earlier for girls. Consistent with theoretical models, teaching occurs for skills/knowledge that cannot be transmitted with high fidelity through other social learning processes such as the acquisition of abstract information e.g. social norms. Whereas, observational and imitative learning occur for the transmission of visually transparent skills such as tool use, foraging, and cooking. These results suggest that coevolutionary relationships between human sociality, language and teaching have likely been fundamental in the emergence of human cumulative culture.

The Neolithic demographic transition remains a paradox, because it is associated with both higher rates of population growth and increased morbidity and mortality rates. Here we reconcile the conflicting evidence by proposing that the spread of agriculture involved a life history quality–quantity trade-off whereby mothers traded offspring survival for increased fertility, achieving greater reproductive success despite deteriorating health. We test this hypothesis by investigating fertility, mortality, health, and overall reproductive success in Agta hunter-gatherers whose camps exhibit variable levels of sedentarization, mobility, and involvement in agricultural activities. We conducted blood composition tests in 345 Agta and found that viral and helminthic infections as well as child mortality rates were significantly increased with sedentarization. Nonetheless, both age-controlled fertility and overall reproductive success were positively affected by sedentarization and participation in cultivation. Thus, we provide the first empirical evidence, to our knowledge, of an adaptive mechanism in foragers that reconciles the decline in health and child survival with the observed demographic expansion during the Neolithic.

Ethnographers frequently allude to alcoholism and related harms in Indigenous hunter-gatherer communities, but very few studies have quantified patterns of alcohol consumption or its health and social impacts. We present a case study of the Mbendjele BaYaka, a Congolese population undergoing socioeconomic transition. 83 adults answered questions about their frequency and quantity of alcohol consumption, underwent biometric measurements and reported whether they were currently experiencing a cough or diarrhoea; 56 participated in structured interviews about their experiences with alcohol. Based on WHO standards, we found 44.3% of the full sample, and 51.5% of drinkers (excluding abstainers), had a hazardous volume of alcohol consumption; and 35.1% of the full sample, and 40.9% of drinkers, engaged in heavy episodic drinking; consumption habits varied with sex and age. Total weekly consumption was a positive predictor of blood pressure and the likelihood of experiencing diarrhoea; associations with other biometric variables were not statistically significant. Interview responses indicated numerous other economic, mental and physical health harms of alcohol use, the prevalence of which demonstrate some variability between forest camps and permanent village settlements. These include high rates of drinking during pregnancy and breastfeeding (~40%); frequent alcohol-induced violence; and considerable exchange of foraged foods and engagement in exploitative labour activities to acquire alcohol or repay associated debts. Our findings demonstrate the prevalence of hazardous alcohol consumption among transitioning hunter-gatherers is higher than other segments of the Congolese population and indicate negative impacts on health and wellbeing, highlighting an urgent need for targeted public health interventions.

The diversity of microbial species in a metagenomic study is commonly assessed using 16S rRNA gene sequencing. With the rapid developments in genome sequencing technologies, the focus has shifted towards the sequencing of hypervariable regions of 16S rRNA gene instead of full length gene sequencing. Therefore, 16S Classifier is developed using a machine learning method, Random Forest, for faster and accurate taxonomic classification of short hypervariable regions of 16S rRNA sequence. It displayed precision values of up to 0.91 on training datasets and the precision values of up to 0.98 on the test dataset. On real metagenomic datasets, it showed up to 99.7% accuracy at the phylum level and up to 99.0% accuracy at the genus level. 16S Classifier is available freely at http://metagenomics.iiserb.ac.in/16Sclassifier and http://metabiosys.iiserb.ac.in/16Sclassifier.

Individuals’ centrality in their social network (who they and their social ties are connected to) has been associated with fertility, longevity, disease and information transmission in a range of taxa. Here, we present the first exploration in humans of the relationship between reproductive success and different measures of network centrality of 39 Agta and 38 BaYaka mothers. We collected three-meter contact (‘proximity’) networks and reproductive histories to test the prediction that individual centrality is positively associated with reproductive fitness (number of living offspring). Rather than direct social ties influencing reproductive success, mothers with greater indirect centrality (i.e. centrality determined by second and third degree ties) produced significantly more living offspring. However, indirect centrality is also correlated with sickness in the Agta, suggesting a trade-off. In complex social species, the optimisation of individuals’ network position has important ramifications for fitness, potentially due to easy access to different parts of the network, facilitating cooperation and social influence in unpredictable ecologies.

Human children are frequently cared for by non-parental caregivers (alloparents), yet few studies have conducted systematic alternative hypothesis tests of why alloparents help. Here we explore whether predictions from kin selection, reciprocity, learning-to-mother and costly signalling hypotheses explain non-parental childcare among Agta hunter-gatherers from the Philippines. To test these hypotheses, we used high-resolution proximity data from 1,701 child–alloparent dyads. Our results indicated that reciprocity and relatedness were positively associated with the number of interactions with a child (our proxy for childcare). Need appeared more influential in close kin, suggesting indirect benefits, while reciprocity proved to be a stronger influence in non-kin, pointing to direct benefits. However, despite shared genes, close and distant kin interactions were also contingent on reciprocity. Compared with other apes, humans are unique in rapidly producing energetically demanding offspring. Our results suggest that the support that mothers require is met through support based on kinship and reciprocity. Cross-culturally, humans have extensive childcare systems that help parents raise their children. Page et al. examine 1,701 alloparent–child dyads in Agta people, finding that both kin selection and reciprocity are important predictors of alloparenting.

Thyroid disorders range from localized lesions, such as colloid goiter, to autoimmune thyroiditis and can present as a tumour mass. Despite a huge number of lesions, they should be classified into two basic categories: one with a diffuse pattern of involvement and the other that results in thyroid gland nodules. Thyroid nodules are frequently found in clinical settings, accounting for 4-7% of the adult population. Thyroiditis, along with hyperplasia, generally affects the entire gland, which is linked to diffuse expansion of the thyroid. Many disorders, including thyroid conditions, can be effectively managed, and their progression can be largely prevented through a well-functioning immune system. Neutrophil-lymphocyte ratio (NLR) and absolute lymphocyte count (ALC) are markers of systemic inflammatory response. There is a paucity of literature available on the correlation of NLR and ALC with thyroiditis compared to other benign thyroid disorders. Current research was conducted to depict the diagnostic utility of NLR and ALC in differentiating between thyroiditis and other benign causes of thyroid enlargement. This is a case-control study conducted from November 2022 to April 2024 (for a period of 18 months). Data were collected from patients with thyroid swelling who underwent fine needle aspiration cytology (ultrasonography-guided or non-USG-guided) from the cytopathology section. Data on the hematological parameters of the same patients were collected from the hematology section after considering the inclusion and exclusion criteria. Data were entered into an MS Excel sheet (Microsoft® Corp., Redmond, WA) and evaluated using SPSS (version 24; IBM SPSS Statistics for Windows, Armonk, NY). In the current research, a total of 136 samples were taken. Out of 136 samples, 121 (89.0%) were women, and 15 (11.0%) were men. Hashimoto's thyroiditis (HT) constituted 18.4% (25 cases), and the rest were benign causes of thyroid enlargement, as a control group (81.6%, 111 controls). The mean age for HT was 36.44±12.81 years, while it was 38.45±12.62 years in the control group. The mean total leukocyte count (TLC) for HT was 8651.20±2378.03 cells/cumm, and for the control group, it was 7367.30±2204.37 cells/cumm. The p-value for TLC was 0.011. The mean neutrophil and lymphocyte percentages for HT were 65.44±11.92 and 28±11.31, respectively, while in the control group, it was 68.23±10.44 and 25.91±8.77, respectively. The results obtained for the NLR were 3.17±2.84 in HT and 3.26±2.38 in the control group. The mean of ALC in HT was 2379.32±1137.53 cells/cumm, and in the control group, it was 1843.14±674.35 cells/cumm. The p-value for ALC was 0.002. The results were statistically significant for the total leukocyte count and ALC. The gold standard in the assessment of thyroid disorders is histopathological examination, as the NLR is not specific for thyroid disorders, and this should not be considered as a diagnostic test alone. The NLR, although a cheap and noninvasive marker, has limited value in the diagnosis of thyroid disorders, while the ALC provides additional specificity to this inflammatory profile, which showed significant results in current research. More studies and other inflammatory markers with large sample sizes are needed to establish the correlation between ALC and different thyroid disorders.