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BackgroundThe spike protein of SARS-CoV-2 engages the human angiotensin-converting enzyme 2 (ACE2) receptor to enter host cells, and neutralizing antibodies are effective at blocking this interaction to prevent infection. Widespread application of this important marker of protective immunity is limited by logistical and technical challenges associated with live virus methods and venous blood collection. To address this gap, we validated an immunoassay-based method for quantifying neutralization of the spike-ACE2 interaction in a single drop of capillary whole blood, collected on filter paper as a dried blood spot (DBS) sample.MethodsSamples are eluted overnight and incubated in the presence of spike antigen and ACE2 in a 96-well solid phase plate. Competitive immunoassay with electrochemiluminescent label is used to quantify neutralizing activity. The following measures of assay performance were evaluated: dilution series of confirmed positive and negative samples, agreement with results from matched DBS-serum samples, analysis of results from DBS samples with known COVID-19 status, and precision (intra-assay percent coefficient of variation; %CV) and reliability (inter-assay; %CV).ResultsDilution series produced the expected pattern of dose-response. Agreement between results from serum and DBS samples was high, with concordance correlation = 0.991. Analysis of three control samples across the measurement range indicated acceptable levels of precision and reliability. Median % neutralization was 46.9 for PCR confirmed convalescent COVID-19 samples and 0.1 for negative samples.ConclusionsLarge-scale testing is important for quantifying neutralizing antibodies that can provide protection against COVID-19 in order to estimate the level of immunity in the general population. DBS provides a minimally-invasive, low cost alternative to venous blood collection, and this scalable immunoassay-based method for quantifying neutralization of the spike-ACE2 interaction can be used as a surrogate for virus-based assays to expand testing across a wide range of settings and populations.

Circulating testosterone (T) follows a diurnal pattern with high waking levels that decline across the day. The hypothalamic-pituitary-adrenal axis produces cortisol in a similar manner but also undergoes an abrupt increase in hormone secretion immediately upon waking (a cortisol awakening response, CAR). Whether the hypothalamic-pituitary-gonadal axis, and circulating T levels, exhibit a similar post-waking response is unclear. Here we describe post-waking T changes in a sample of 108 young adult males from metropolitan Cebu City, the Philippines. As expected, salivary T was higher at waking than in the evening but, remarkably, 60 % of this diurnal decline occurred within 30 min of awakening. There was a strong inverse linear relationship between waking T and the post-waking T decline, such that men with higher waking T experienced a more rapid decline in the hormone. Even though fathers had lower waking T, they experienced a greater post-waking decline than non-fathers. Men with a larger positive CAR had modestly attenuated post-waking T declines. We speculate that these findings reflect a testosterone awakening response (TAR) that helps partition the target tissue effects of T by time of day. T rises overnight to facilitate muscle anabolism at a time when the hormone’s impacts on social behavior are limited. Upon waking, the rapid drop in T helps shift from anabolic to catabolic processes in support of physical activity, while also calibrating T levels in line with the competing social priorities of the individual, as determined by the current balance of behavioral investment towards mating and parental effort.

Cumulative exposure to chronic stressors has been shown to contribute to immigrants' deteriorating health with more time in US residence. Few studies, however, have examined links among common psychosocial stressors for immigrants (e.g., acculturation-related) and contexts of immigrant settlement for physical health. The study investigated relationships among social stressors, stress buffers (e.g., family support), and allostatic load (AL)--a summary measure of physiological "wear and tear"--among 126 adult Mexican immigrant farm workers. Analyses examined social contributors to AL in two locales: (1) White, English-speaking majority sites, and (2) a Mexican immigrant enclave. Our six-point AL scale incorporated immune, cardiovascular, and metabolic measures. Among men and women, older age predicted higher AL. Among women, lower family support related to higher AL in White majority communities only. Findings suggest that Latino immigrants' cumulative experiences in the US significantly compromise their health, with important differences by community context.

Past paternal psychobiology research has focused almost exclusively on biological, residential fathers and the role of fathers as direct caregivers. Here, drawing on a large sample of Filipino men, we help to expand this research area by testing for relationships between fathers’ testosterone, prolactin, and weekly hours in work, childcare, and recreation. Using longitudinal data collected when men were an average of 21.5 and 26.0 years old, we tested whether changes in fathers’ investments in childcare and work interrelated with testosterone changes. We also assessed whether fathers’ residence status affected paternal testosterone changes. Cross-sectionally, we did not find evidence that fathers’ testosterone or prolactin varied based on work effort or weekly hours of childcare (all p > 0.1). Fathers who increased their weekly involvement in childcare between baseline and follow-up experienced declines in testosterone, on average (p

Testosterone contributes to male life history trade-offs through effects on behavior and energy usage. Testosterone’s role as a trade-off mediator is often discussed as manifesting partly through a negative impact on investment in survival, via immune suppression. Studies across species also show that testosterone in males commonly fluctuates with social changes, providing natural experiments to evaluate any potential immune impacts of intraindividual changes in testosterone. Using longitudinal data from Metropolitan Cebu City, the Philippines, we recently showed that men transitioning to fatherhood experienced substantial declines in testosterone over a 4.5-yr period. Drawing on a subsample of the same men here (N = 330), we evaluate whether these socially mediated changes in testosterone are paralleled by changes in immune function as reflected in salivary secretory immunoglobulin A (SIgA), a localized marker of mucosal immunity. Men reporting more cold/flu symptoms had lower testosterone and a trend toward lower SIgA in cross-section. Intraindividual changes in testosterone between baseline and follow-up 4.5 yr later were strong, positive predictors of changes in SIgA. Men becoming new fathers did not differ in ΔSIgA compared to other men. The positive relationship between ΔSIgA and ΔT in this sample runs counter to the expectation of a mating–maintenance trade-off, and may reflect direct effects of androgens on SIgA production. Our results add to the dialogue on the complex relationships between the reproductive and immune axes, providing additional evidence that in humans testosterone is not uniformly immunosuppressive.

Researchers have hypothesized that the degree to which an individual's actual behavior approximates the culturally valued lifestyle encoded in the dominant cultural model has consequences for physical and mental health. We contribute to this line of research by analyzing data from a longitudinal study composed of five annual surveys (2002-2006 inclusive) of 791 adults in one society of foragers-farmers in the Bolivian Amazon, the Tsimane'. We estimate the association between a standard measure of individual achievement of the cultural model and (a) four indicators of psychological well-being (sadness, anger, fear and happiness) and (b) consumption of four potentially addictive substances (alcohol, cigarette, coca leaves and home-brewed beer) as indicators of stress behavior. After controlling for individual fixed effects, we found a negative association between individual achievement of the cultural model and psychological distress and a positive association between individual achievement of the cultural model and psychological well-being. Only the consumption of commercial alcohol bears the expected negative association with cultural consonance in material lifestyle, probably because the other substances analyzed have cultural values attached. Our work contributes to research on psychological health disparities by showing that a locally defined and culturally specific measure of lifestyle success is associated with psychological health.

Previous research addressing the association between leisure and happiness has given rise to the hypothesis that informal social activities might contribute more to happiness than solitary activities. In the current study, we tested how the two types of leisure—social and solitary—contribute to a person’s subjective sense of well-being. For the empirical estimate, we used four consecutive quarters of data collected from 533 people over the age of 16, from 13 Tsimane’ hunter-farmer villages in the Bolivian Amazon. Results suggest that only social, not solitary, leisure has a positive and statistically significant association with subjective well-being. The association between solitary leisure and subjective well-being was negligible or negative. Future research should focus on emic definitions of social and solitary time, for solitary time might not always be equivalent to leisure and productive group activities might substitute for social leisure.

Unlike neighboring disciplines, anthropology rarely studies how actual future events affect current behavior. Such studies could lay the groundwork for studies of ethno-forecasting. Psychologists argue that people forecast poorly, but some empirical work in cultural anthropology suggests that at least with weather, rural people might make reasonably accurate forecasts. Using data from a small-scale, pre-industrial rural society in the Bolivian Amazon, this study estimates the effects of future weather on the current collection of planted crops and wildlife. If actual future events affect current behavior, then this would suggest that people must forecast accurately. Longitudinal data covering 11 consecutive months (10/2002–8/2003, inclusive) from 311 women and 326 men ≥age 14 in 13 villages of a contemporary society of forager-farmers in Bolivia’s Amazon (Tsimane’) are used. Individual fixed-effect panel linear regressions are used to estimate the effect of future weather (mean hourly temperature and total daily rain) over the next 1–7 days from today on the probability of collecting wildlife (game, fish, and feral plants excluding firewood) and planted farm crops (annuals and perennials) today. Daily weather records come from a town next to the Tsimane’ territory and data on foraging and farming come from scans (behavioral spot observations) and surveys of study participants done during scans. Short-term future weather (≤3 days) affected the probability of collecting planted crops and wildlife today, although the effect was greater on the amount of planted crops harvested today than on the amount of wildlife collected today. Future weather beyond 3 days bore no significant association with the amount of planted crops harvested today nor with the amount of wildlife collected today. After controlling for future and past weather, today’s weather (mean hourly temperature, but not rain) affected the probability of collecting wildlife today, but today’s weather (temperature or rain) did not affect the probability of collecting planted crops today. The study supports prior work by anthropologists suggesting that rural people forecast accurately. If future weather affects the probability of harvesting planted crops and collecting wildlife today, then this suggests that Tsimane’ must forecast accurately. We discuss possible reasons for the finding. The study also supports growing evidence from rural areas of low-income nations that rural people tend to protect their food production and food consumption well against small idiosyncratic shocks or, in our case, against ordinary daily weather that is not extreme. However, the greater responsiveness of daily foraging output compared with daily farming output to today’s weather suggests that foraging might not protect food consumption as well as farming against adverse climate perturbations

Despite the growing interest in the topic, there has been little quantitative research about the causes and rate of acquisition and loss of local ecological knowledge. Some researchers have linked the loss of local ecological knowledge to the expansion of the market economy (Godoy et al., 1998; Ross, 2002; Reyes-Garcia et al., 2005a), others have found persistence in local ecological knowledge despite large socio-economic changes (Zarger and Stepp, 2004), and still others have found that integration into the market economy through an economic activity based in the natural environment could accelerate the acquisition of local ecological knowledge (Guest, 2002). The debate matters for policy-making because if integration to the market erodes local knowledge, there would be no possibility of simultaneously achieving conservation of local knowledge and economic development. In contrast, if integration to the market economy does not affect or does not always affect local knowledge, then some forms of market incorporation could develop without eroding local ecological knowledge. In this article we test how various forms of integration to the market economy affect local ecological knowledge. Local knowledge has many domains (i.e., myth, cosmology), including local ecological knowledge, which itself comprises many subdomains, such as plants, animals, insects, or soils. We proxy local ecological knowledge with ethnobotanical knowledge. We use a new way of measuring ethnobotanical knowledge that stresses skills that draw on ethnobotanical knowledge, and compare results with standard measures of ethnobotanical knowledge that stress passive knowledge. We hypothesize that only some forms of integration to the market economy, namely activities that take individuals out of their culture and environment, are associated with less local ecological knowledge. To explore the topic, we draw on information from 476 Tsimane’—a foraging-horticultural society in the Bolivian Amazon.

Growing evidence suggests mothers invest more in girls than boys and fathers more in boys than girls. We develop a hypothesis that predicts preference for girls by the parent facing more resource constraints and preference for boys by the parent facing less constraint. We test the hypothesis with panel data from the Tsimane', a foraging-farming society in the Bolivian Amazon. Tsimane' mothers face more resource constraints than fathers. As predicted, mother's wealth protected girl's BMI, but father's wealth had weak effects on boy's BMI. Numerous tests yielded robust results, including those that controlled for fixed effects of child and household.

There is growing interest in assessing how income influences the consumption of wildlife in poor rural areas of developing nations. The interest stems from the possibility of using income to contribute to the conservation of wildlife. Though promising, efforts have been hampered by the difficulty of obtaining accurate measures of income. We propose using human body-mass index (BMI: weight in kilograms/physical stature in m2), an indicator of short-term nutritional status, as a proxy variable for monetary income to estimate income elasticities of wildlife consumption (income elasticity: percent change in wildlife consumption/one-percent change income). The advantages of BMI over monetary income include a positive association with monetary income, ease of measurement, and absence of zero values. The assessment procedure was tested among Tsimane’ Amerindians, a society of foragers and farmers in the Bolivian Amazon. The population over 15 years of age (350 men and 322 women) in 13 villages was surveyed for five consecutive quarters (August 2002–November 2003). Income elasticities of wildlife consumption using BMI as a proxy for income ranged from −0.84 to −1.20. The estimates suggest that wildlife is a food item whose consumption declines with increasing income. Estimates of income elasticity of wildlife consumption using conventional indices of monetary income are negative, but lower and indistinguishable from zero owing to classical measurement errors of monetary income. The use of BMI to estimate income elasticities of wildlife consumption is promising, but requires further validation in different settings.