Human biology and the study of precarity: How the intersection of uncertainty and inequality is taking us to new extremes.

Inequality represents an extreme environment to which humans must respond. One phenomenon that contributes to this growing extreme is precarity or the intersection of uncertainty and some form of inequality. While precarity has an important intellectual history in the fields of sociology and sociocultural anthropology, it has not been well studied in the field of human biology. Rather human biologists have engaged with the study of closely related concepts such as uncertainty and resource insecurity. In this article, we propose that human biology take on the study of precarity as a novel way of investigating inequality. We first provide a brief intellectual history of precarity which is followed by a review of research on uncertainty and resource security in human biology which, while not exhaustive, illustrates some key gaps that precarity may aid us in addressing. We then review some of the pathways through which precarity comes to affect human biology and health and some of the evidence for why the unpredictable nature of precarity may make it a unique physiological stress. A case study based on research in Nuñoa, Peru provides an important example of how precarity can elucidate the influences of health in an extreme setting, albeit with insights that apply more broadly. We conclude that precarity holds important potential for the study of human biology, including helping us more effectively operationalize and study uncertainty, encouraging us to explore the predictability of resources and stressors, and reminding us to think about the intersectional nature of stressors.

Genome-wide analysis of DNA methylation in relation to socioeconomic status during development and early adulthood.

OBJECTIVES: Socioeconomic status (SES) is a powerful determinant of health, but the underlying biological mechanisms are poorly understood. This study investigates whether levels of DNA methylation at CpG sites across the genome are associated with SES in a cohort of young adults in the Philippines. METHODS: DNA methylation was assayed with the Illumina HumanMethylation450 Bead Chip, in leukocytes from 489 participants in the Cebu Longitudinal Health and Nutrition Survey (mean age = 20.9 years). SES was measured in infancy/childhood and adulthood, and was based on composite measures of income, assets, and education. Genome-wide analysis of variable probes identified CpG sites significantly associated with SES after adjustment for multiple comparisons. Functional enrichment analysis was used to identify biological pathways associated with these sites. RESULTS: A total of 2,546 CpG sites, across 1,537 annotated genes, were differentially methylated in association with SES. In comparison with high SES, low SES was associated with increased methylation at 1,777 sites, and decreased methylation at 769 sites. Functional enrichment analysis identified over-representation of biological pathways related to immune function, skeletal development, and development of the nervous system. CONCLUSIONS: Socioeconomic status predicts DNA methylation at a large number of CpG sites across the genome. The scope of these associations is commensurate with the wide range of biological systems and health outcomes that are shaped by SES, and these findings suggest that DNA methylation may play an important role.

Secular trends in growth in the high-altitude district of Nuñoa, Peru 1964-2015.

OBJECTIVES: Nuñoa, Peru has been the site of anthropological research on human adaptability, growth, and health since the 1960s. Previous studies documented a nascent secular trend in growth between 1964 and 1984. However, no secular trend was evident when the population was re-examined in 1999, following an intervening period of sociopolitical upheaval. Subsequently, the region experienced considerable economic development reflected in secular increases in height. We seek to evaluate trends in growth and BMI among Nuñoan children over 50 years. MATERIALS AND METHODS: Anthropometric data for 929 children collected in 2015 are compared with anthropometric data for 394 children from 1964, 912 children from 1984, and 292 children from 1999. The data were converted to z-scores using the WHO 2007 growth standards. anova is used to evaluate rates of stunting, underweight, overweight, and obesity across the study periods. RESULTS: We observe small increases in stature and weight between the 1960s and 1980s, almost no change between the 1980s and 1990s and statistically significant reductions in stunting and increases in height between the 1990s and 2015. DISCUSSION: There were relatively small differences in stature and weight and a high incidence of stunting between 1964 and 1999 attributed to extremely poor economic and health conditions. A large secular increase in height (7-8 cm on average) and consequent reduction in rates of stunting between 1999 and 2015 occurred due to improved social and economic conditions. In addition to political stabilization, enhanced infrastructure, social aid programs, improved healthcare, and economic expansion contribute to these trends.

Economic activity and patterns of infant growth in a high altitude district of Peru.

OBJECTIVES: Changing economic activities bring significant cultural, epidemiological, and nutritional transitions. Infancy represents a critical period when rapid growth and metabolic programming occur, making infants particularly vulnerable to long-lasting biological changes due to such transitions. This paper examines the relationship between residence in distinct economic production zones (urban, herding, and dairy) and early growth in a highland district of Peru. METHODS: The length, weight, body mass index, and triceps skinfold of 93 infants (55 boys and 38 girls, aged 2 to 24 months) from 3 economic zones were measured at two time points 6 months apart. Z-scores were calculated based on the WHO Growth Reference for children under 5 years of age. Comparisons were made to the reference group and between economic zones to examine the impacts of different economic activities on infant growth. RESULTS: Female infants had significantly higher height-for-age z-scores (HAZ) than males (P < 0.05). Across zones, dairying infants had the highest HAZ scores and the lowest prevalence of stunting. There was a significant association between zone and HAZ at baseline. While these associations were attenuated in measurements, taken 6 months later, longitudinal growth monitoring revealed differential patterns of weight gain and adiposity deposition across the zones with herding infants showing consistent high adiposity and urban infants gaining both weight and adiposity between rounds. DISCUSSION: Changes in economic activity are bringing about nutritional and epidemiological transitions in the Nuñoa district. Economic activity is a key factor influencing early growth with distinct longitudinal growth patterns in each economic zone.