Uncertainty in a globalizing world. Livelihood and fertility variance increases in response to rapid change.

OBJECTIVES: The extreme condition that we address in this special issue is how people adapt to rapid change, which in this case study is instigated by globalization and the process of market integration. Although market integration has been underway for centuries in some parts of the world, it often occurs precipitously in small-scale societies, initiating an abrupt break with traditional ways of life and fostering a keen sense of uncertainty. METHODS: Using cross sections from 30-years of data collected in a Yucatec Maya subsistence farming community, we test the expectation that when payoffs to pursue new livelihood and reproductive options are uncertain, variance in social, economic, and reproductive traits will increase in the population. Our data span the transition from subsistence farming to a mixed economy, and bridge the transition from natural to contracepting fertility. Exposure to globalizing and market forces occurred when a paved road was built in the early 2000s. RESULTS: We find that livelihood traits (a household's primary economic strategy, amount of land under cultivation, amount of maize and honey sold), become more variable as new, but uncertain options become available. Variance in levels of education and family size likewise immediately increase following the road, but show signs of settling back down a decade later. Rather than replacing one way of life with another, Maya farmers conservatively adopt some new elements (family planning, wage labor), until the tradeoffs to commit to smaller families and the labor market become clearer. CONCLUSION: Our findings highlight that in rapidly changing environments when the payoffs to assimilate new options are uncertain, some households and individuals intensify what they know best, while others adopt new opportunities, driving variance up in the population.

Sex differences in adipose development in a hunter-gatherer population.

OBJECTIVE: Humans are unusually sexually dimorphic in body composition, with adult females having on average nearly twice the fat mass as males. The development of adipose sex differences has been well characterized for children growing up in food-abundant environments, with less known about cross-cultural variation, particularly in populations without exposure to market foods, mechanized technologies, schooling, vaccination, or other medical interventions. METHODS: To add to the existing cross-cultural data, we fit multiple growth curves to body composition and anthropometric data to describe adipose development for the Savanna Pumé, South American hunter-gatherers. RESULTS: (1) Little evidence is found for an adiposity 'rebound' at the end of early childhood among either Savanna Pumé girls or boys. (2) Rather, fat deposition fluctuates during childhood, from age ~4 to ~9 years, with no appreciable accumulation until the onset of puberty, a pattern also observed among Congo Baka hunter-gatherers. (3) Body fat fluctuations are more pronounced for girls than boys. (4) The age of peak skeletal, weight, and adipose gains are staggered to a much greater extent among the Savanna Pumé compared to the National Health and Nutrition Examination Survey (NHANES III) reference, suggesting this is an important developmental strategy in lean populations. CONCLUSION: Documenting growth patterns under diverse preindustrial energetic conditions provides an important baseline for understanding sex differences in body fat emerging today under food abundance.

Scaling climate change to human behavior predicting good and bad years for Maya farmers.

OBJECTIVES: Human responses to climate variation have a rich anthropological history. However, much less is known about how people living in small-scale societies perceive climate change, and what climate data are useful in predicting food production at a scale that affects daily lives. METHODS: We use longitudinal ethnographic interviews and economic data to first ask what aspects of climate variation affect the agricultural cycle and food production for Yucatec Maya farmers. Sixty years of high-resolution meteorological data and harvest assessments are then used to detect the scale at which climate data predict good and bad crop yields, and to analyze long-term changes in climate variables critical to food production. RESULTS: We find that (a) only local, daily precipitation closely fits the climate pattern described by farmers. Other temporal (annual and monthly) scales miss key information about what farmers find important to successful harvests; (b) at both community- and municipal-levels, heavy late-season rains associated with tropical storms have the greatest negative impact on crop yields; and (c) in contrast to long-term patterns from regional and state data, local measures show an increase in rainfall during the late growing season, indicating that fine-grained data are needed to make accurate inferences about climate trends. CONCLUSION: Our findings highlight the importance to define climate variables at scales appropriate to human behavior. Course-grained annual, monthly, national, and state-level data tell us little about climate attributes pertinent to farmers and food production. However, high-resolution daily, local precipitation data do capture how climate variation shapes food production.

Body norms and normative bodies in Highland Guatemala.

OBJECTIVES: The concept of bionormalcy highlights the potential tensions between bodies defined clinically as normal or healthy, bodies that are normative (frequent) within a population, and bodies defined within a given social context as abnormal or devalued. Theories of resource scarcity predict preferences for larger bodies should deviate from what is biologically normative (i.e., most frequent) or clinically defined as healthy. Using the case of adult women in a Guatemalan community with chronically low food security, we test how food scarcity shapes individual views of smaller, larger, and clinically categorized normal bodies. METHODS: Participants were 102 women from a community in the Central Highlands of Guatemala. Using the Stunkard figure scale and a word elicitation task, participants attributed positive and negative characteristics to male and female silhouettes clinically defined as underweight, normal, overweight, mildly obese, and obese. Mixed-effects models were used to compare attribution scores for figures relative to the clinically normal silhouette. RESULTS: Silhouettes deviating from the clinically defined normal BMI category on both sides are stigmatized to varying degrees. Food insecurity exacerbates the degree of stigma, while also relatively preferencing overweight bodies. CONCLUSIONS: In this pilot study, women exhibit a preference for body sizes that fall within the clinical normal and overweight categories and stigmatize bodies outside this range, but in distinct ways. We suggest the attachment of stigma to small and large bodies are not mirror processes, and require more detailed testing to untangle the likely complex ecological and social explanations.

How can evolutionary and biological anthropologists engage broader audiences?

OBJECTIVES: With our diverse training, theoretical and empirical toolkits, and rich data, evolutionary and biological anthropologists (EBAs) have much to contribute to research and policy decisions about climate change and other pressing social issues. However, we remain largely absent from these critical, ongoing efforts. Here, we draw on the literature and our own experiences to make recommendations for how EBAs can engage broader audiences, including the communities with whom we collaborate, a more diverse population of students, researchers in other disciplines and the development sector, policymakers, and the general public. These recommendations include: (1) playing to our strength in longitudinal, place-based research, (2) collaborating more broadly, (3) engaging in greater public communication of science, (4) aligning our work with open-science practices to the extent possible, and (5) increasing diversity of our field and teams through intentional action, outreach, training, and mentorship. CONCLUSIONS: We EBAs need to put ourselves out there: research and engagement are complementary, not opposed to each other. With the resources and workable examples we provide here, we hope to spur more EBAs to action.

Learning from failures of protocol in cross-cultural research.

The many tools that social and behavioral scientists use to gather data from their fellow humans have, in most cases, been honed on a rarefied subset of humanity: highly educated participants with unique capacities, experiences, motivations, and social expectations. Through this honing process, researchers have developed protocols that extract information from these participants with great efficiency. However, as researchers reach out to broader populations, it is unclear whether these highly refined protocols are robust to cultural differences in skills, motivations, and expected modes of social interaction. In this paper, we illustrate the kinds of mismatches that can arise when using these highly refined protocols with nontypical populations by describing our experience translating an apparently simple social discounting protocol to work in rural Bangladesh. Multiple rounds of piloting and revision revealed a number of tacit assumptions about how participants should perceive, understand, and respond to key elements of the protocol. These included facility with numbers, letters, abstract number lines, and 2D geometric shapes, and the treatment of decisions as a series of isolated events. Through on-the-ground observation and a collaborative refinement process, we developed a protocol that worked both in Bangladesh and among US college students. More systematic study of the process of adapting common protocols to new contexts will provide valuable information about the range of skills, motivations, and modes of interaction that participants bring to studies as we develop a more diverse and inclusive social and behavioral science.

Disentangling basal and accrued height-for-age for cross-population comparisons.

OBJECTIVES: Current standards for comparing stunting across human populations assume a universal model of child growth. Such comparisons ignore population differences that are independent of deprivation and health outcomes. This article partitions variation in height-for-age that is specifically associated with deprivation and health outcomes to provide a basis for cross-population comparisons. MATERIALS AND METHODS: Using a multilevel model with a sigmoid relationship of resources and growth, we partition variation in height-for-age z-scores (HAZ) from 1.5 million children across 70 countries into two components: (1) "accrued HAZ" shaped by environmental inputs (e.g., undernutrition, infectious disease, inadequate sanitation, poverty) and (2) a country-specific "basal HAZ" independent of such inputs. We validate these components against population-level infant mortality rates and assess how these basal differences may affect cross-population comparisons of stunting. RESULTS: Basal HAZ differs reliably across countries (range of approximately 1.5 SD) and is independent of measures of infant mortality. By contrast, accrued HAZ captures stunting as impaired growth due to deprivation and is more closely associated with infant mortality than observed HAZ. Assessing stunting prevalence by accrued HAZ suggest that populations in West Africa and Haiti suffer much greater levels of stunting than indicated by observed HAZ. DISCUSSION: Current universal standards may dramatically underestimate stunting in populations with taller basal HAZ. Relying on observed HAZ rather than accrued HAZ may also lead to inappropriate cross-population comparisons, such as concluding that Haitian children enjoy better conditions for growth than do Indian or Guatemalan children.

Reproductive preferences during middle childhood and early adolescence in Guatemala.

Reproductive preferences and the spread of low fertility norms occupy a key position in debates regarding the causal mechanisms underlying sustained fertility declines. Most of the literature on reproductive preferences focuses on stability and variability of adult fertility preferences, and their relationship with behavioural outcomes. Little work has focused on the developmental origins of these preferences, particularly in populations undergoing rapid social and demographic change. This study explores the utility of integrating the ontogeny of fertility preferences into accounts of fertility declines. We analyse data on child and adolescent (age 8-15) reproductive preferences collected from a semi-rural community in the Guatemalan Highlands. We explore (1) the distribution of reproductive preferences across age and gender, (2) relationships between family structure and preferences, (3) the relationship between personal economic and occupational aspirations and reproductive preferences, and (4) the effects of parental investments in education on reproductive preferences. Findings reveal the early development of gender and ethnic differences in reported reproductive preferences, as well as evidence for the differential impact of family background and personal aspirations on the timing of reproductive events and ideal family size.

Worldwide fertility declines do not rely on stopping at ideal parities.

A key demographic hypothesis has been that fertility declines rely on stopping at target parities, but emerging evidence suggests that women frequently reduce fertility without specific numeric targets. To assess the relative importance of these two paths to fertility decline, we develop a novel mixture model to estimate: (1) the proportion of women who stop at a target parity; and (2) mean completed fertility among those who do not. Applied to Demographic and Health Survey data from women aged 45-49 in 84 low- and middle-income countries, and to United States Census cohorts, the model shows considerable variation in the proportion stopping at specific parities (1-84 per cent). The estimates also show that declines in completed fertility are largely attributable to women who do not stop at target parities, suggesting that stopping at ideal parities may be less important than parity-independent decisions for a wide range of fertility transitions.

Kin networks and opportunities for reproductive cooperation and conflict among hunter-gatherers.

Little is known about the potential for reproductive conflict among hunter-gatherer populations, who are characterized by bilateral kinship ties, flexible residential mobility, and high offspring mortality. To assess the potential for reproductive conflict, we use longitudinal residence and reproductive history data for two bands of South American foragers. Using multilevel logistic regressions (N = 44 women, N = 712 person years), we examine how yearly measures of (i) camp composition, (ii) distribution of female kin and (iii) a woman's position in a female kinship network impact the likelihood of giving birth or experiencing a child's death. We compare conflict models to a demographic model that accounts for the proportion of women giving birth in a given year. Contrary to conflict models, results show that the odds of giving birth increase with the presence of highly related women. However, the odds of experiencing an offspring death are insensitive to the presence of coresident women. Network measures of closeness and centrality in the female kin network also show no significant effect on reproductive outcomes. Furthermore, chances of both births and deaths increase in years when proportionally more women are giving birth. We argue that demographic stochasticity relating to ecological conditions best predicts reproductive outcomes for women. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.

Food insecurity, morbidity, and susto: Factors associated with depression severity in Guatemala measured with the Personal Health Questionnaire 9.

BACKGROUND: Depression is the largest contributor to non-fatal health loss globally and the majority of this burden occurs in low- and middle-income countries. Yet, estimates of prevalence rates and severity in these contexts may be uncertain due to limited screening, lack of mental health providers, and stigma around mental disorders which may prevent individuals from seeking care. In Guatemala, estimates of depression vary, due in part to the range of screening and diagnostic instruments used and diversity of sample populations. Most studies emphasize personal experiences with violence as a predictor of depression in Guatemala, although high rates of inequality, discrimination, and resource scarcity in the country potentially play a role. AIMS: In this study, we examine factors associated with depression severity categories measured with the Personal Health Questionnaire 9 (PHQ-9) among a random sample of women in a small urban community in the Central Highlands of Guatemala. METHODS: Participants were recruited through a randomized sample of households in a small urban community. Participants completed a questionnaire which included questions on demographics, illness history, food insecurity, and the PHQ-9. In total, 101 women were included in the analysis. RESULTS: Food insecurity, 2-week symptom reporting, and experiencing susto are associated with higher depression severity categories. CONCLUSION: This research highlights need for more research on factors related to the prevalence and severity of mental disorders, and the relationship between mental disorders and cultural constructs of distress, particularly in areas like Guatemala with limited mental health services.

Balancing fertility and livelihood diversity in mixed economies.

Mixed economies provide a unique context for testing theories of fertility change. Because they have a stake in two traditions, mixed-economy households balance the demands of both a labor-based subsistence economy, which benefits from a large family, and a wage-labor economy, which benefits from reduced fertility. Additionally, household size changes over the course of its life-cycle and shapes available economic opportunities. Here we argue that in mixed economies, fertility may reflect opportunities for livelihood diversity rather than simply responding to the restricted socioeconomic benefits of small families. While low fertility may in some cases have an economic benefit, low fertility can also limit the livelihood diversity of a household which is a key strategy for long-term economic success. We test this prediction with longitudinal data from a Maya community undergoing both a sustained decline in fertility and rapid integration into the market economy. Using household-level fertility, number of adults, and livelihood diversity at two time points, we find that household size is positively related to livelihood diversity, which in turn is positively related to household income per-capita. However, household size also has a negative association with income per capita. The results reflect a balancing act whereby households attempt to maximize the economic diversity with as few members as possible. Broadly, these results suggest that theories of fertility decline must account for how households pool resources and diversify economic activities in the face of increasing market integration, treating fertility as both an outcome and an input into economic and reproductive decision-making.

Disentangling wealth effects on fertility in 64 low- and middle-income countries.

Studies have shown mixed associations between wealth and fertility, a finding that has posed ongoing puzzles for evolutionary theories of human reproduction. However, measures of wealth do not simply capture economic capacity, which is expected to increase fertility. They can also serve as a proxy for market opportunities available to a household, which may reduce fertility. The multifaceted meaning of many wealth measures obscures our ability to draw inferences about the relationship between wealth and fertility. Here, we disentangle economic capacity and market opportunities using wealth measures that do not carry the same market-oriented biases as commonly used asset-based measures. Using measures of agricultural and market-based wealth for 562,324 women across 111,724 sampling clusters from 151 DHS surveys in 64 countries, we employ a latent variable structural equation model to estimate (a) latent variables capturing economic capacity and market opportunity and (b) their effects on completed fertility. Market opportunities had a consistent negative effect on fertility, while economic capacity had a weaker but generally positive effect on fertility. The results show that the confusion between operational measures of wealth and the concepts of economic capacity can impede our understanding of how material resources and market contexts shape reproduction.

Generalizability is not optional: insights from a cross-cultural study of social discounting.

Current scientific reforms focus more on solutions to the problem of reliability (e.g. direct replications) than generalizability. Here, we use a cross-cultural study of social discounting to illustrate the utility of a complementary focus on generalizability across diverse human populations. Social discounting is the tendency to sacrifice more for socially close individuals-a phenomenon replicated across countries and laboratories. Yet, when adapting a typical protocol to low-literacy, resource-scarce settings in Bangladesh and Indonesia, we find no independent effect of social distance on generosity, despite still documenting this effect among US participants. Several reliability and validity checks suggest that methodological issues alone cannot explain this finding. These results illustrate why we must complement replication efforts with investment in strong checks on generalizability. By failing to do so, we risk developing theories of human nature that reliably explain behaviour among only a thin slice of humanity.

Identifying the limits to socioeconomic influences on human growth.

Contemporary humans occupy the widest range of socioeconomic environments in their evolutionary history, and this has revealed unprecedented environmentally-induced plasticity in physical growth. This plasticity also has limits, and identifying those limits can help researchers: (1) parse when population differences arise from environmental inputs or not and (2) determine when it is possible to infer socioeconomic disparities from disparities in body form. To illustrate potential limits to environmental plasticity, we analyze body mass index (BMI) and height data from 1,768,962 women and 207,341 men (20-49 y) living in households exhibiting 1000-fold variation in household wealth (51 countries, 1985-2017, 164 surveys) across four world regions-sub-Saharan Africa, South Asia, Latin America, and North Africa and the Middle East. We find that relationships of environmental inputs with both mean height and BMI bottom out at roughly 100-700 USD per capita household wealth (2011 international units, PPP), but at different basal BMIs and basal heights for different regions. The relationship with resources tops out for BMI at around 20 K-35 K USD for women, with growth potential due to environmental inputs in the range of 6.2-8.4 kg/m2. By contrast, mean BMI for men and mean height for both sexes remains sensitive to environmental inputs even at levels far above the low- and middle-income samples studied here. This suggest that further work integrating comparable data from low- and high-income samples should provide a better picture of the full range of environmental inputs on human height and BMI. We conclude by discussing how neglecting such population-specific limits to human growth can lead to erroneous inferences about population differences.

Material wealth in 3D: Mapping multiple paths to prosperity in low- and middle- income countries.

Material wealth is a key factor shaping human development and well-being. Every year, hundreds of studies in social science and policy fields assess material wealth in low- and middle-income countries assuming that there is a single dimension by which households can move from poverty to prosperity. However, a one-dimensional model may miss important kinds of prosperity, particularly in countries where traditional subsistence-based livelihoods coexist with modern cash economies. Using multiple correspondence analysis to analyze representative household data from six countries-Nepal, Bangladesh, Ethiopia, Kenya, Tanzania and Guatemala-across three world regions, we identify a number of independent dimension of wealth, each with a clear link to locally relevant pathways to success in cash and agricultural economies. In all cases, the first dimension identified by this approach replicates standard one-dimensional estimates and captures success in cash economies. The novel dimensions we identify reflect success in different agricultural sectors and are independently associated with key benchmarks of food security and human growth, such as adult body mass index and child height. The multidimensional models of wealth we describe here provide new opportunities for examining the causes and consequences of wealth inequality that go beyond success in cash economies, for tracing the emergence of hybrid pathways to prosperity, and for assessing how these different pathways to economic success carry different health risks and social opportunities.

Revisiting Psychological Mechanisms in the Anthropology of Altruism.

Anthropologists have long been interested in the reasons humans choose to help some individuals and not others. Early research considered psychological mediators, such as feelings of cohesion or closeness, but more recent work, largely in the tradition of human behavioral ecology, shifted attention away from psychological measures to clearer observables, such as past behavior, genetic relatedness, affinal ties, and geographic proximity. In this paper, we assess the value of reintegrating psychological measures-perceived social closeness-into the anthropological study of altruism. Specifically, analyzing social network data from four communities in rural Bangladesh (N = 516), we show that perceived closeness has a strong independent effect on helping, which cannot be accounted for by other factors. These results illustrate the potential value of reintegrating proximate psychological measures into anthropological studies of human cooperation.

Weight-related stigma is a significant psychosocial stressor in developing countries: Evidence from Guatemala.

Weight-related stigma is established as a major psychosocial stressor and correlate of depression among people living with obesity in high-income countries. Anti-fat beliefs are rapidly globalizing. The goal of the study is to (1) examine how weight-related stigma, enacted as teasing, is evident among women from a lower-income country and (2) test if such weight-related stigma contributes to depressive symptoms. Modeling data for 12,074 reproductive-age women collected in the 2008-2009 Guatemala National Maternal-Infant Health Survey, we demonstrate that weight-related teasing is (1) experienced by those both underweight and overweight, and (2) a significant psychosocial stressor. Effects are comparable to other factors known to influence women's depressive risk in lower-income countries, such as living in poverty, experiencing food insecurity, or suffering sexual/domestic violence. That women's failure to meet local body norms-whether they are overweight or underweight-serves as such a strong source of psychological distress is particularly concerning in settings like Guatemala where high levels of over- and under-nutrition intersect at the household and community level. Current obesity-centric models of weight-related stigma, developed from studies in high-income countries, fail to recognize that being underweight may create similar forms of psychosocial distress in low-income countries.