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To address claims of human exceptionalism, we determine where humans fit within the greater mammalian distribution of reproductive inequality. We show that humans exhibit lower reproductive skew (i.e., inequality in the number of surviving offspring) among males and smaller sex differences in reproductive skew than most other mammals, while nevertheless falling within the mammalian range. Additionally, female reproductive skew is higher in polygynous human populations than in polygynous nonhumans mammals on average. This patterning of skew can be attributed in part to the prevalence of monogamy in humans compared to the predominance of polygyny in nonhuman mammals, to the limited degree of polygyny in the human societies that practice it, and to the importance of unequally held rival resources to women's fitness. The muted reproductive inequality observed in humans appears to be linked to several unusual characteristics of our species-including high levels of cooperation among males, high dependence on unequally held rival resources, complementarities between maternal and paternal investment, as well as social and legal institutions that enforce monogamous norms.

The goal of assessing psychosocial stress as a process and outcome in naturalistic (i.e., field) settings is applicable across the social, biological, and health sciences. Meaningful measurement of biology-in-context is, however, far from simple or straightforward. In this brief methods review, we introduce theoretical framings, methodological conventions, and ethical concerns around field-collection of markers of psychosocial stress that have emerged from 50 years of research at the intersection of anthropology and human biology. Highlighting measures of psychosocial stress outcomes most often used in biocultural studies, we identify the circumstances under which varied measures are most appropriately applied and provide examples of the types of cutting-edge research questions these measures can address. We explain that field-based psychosocial stress measures embedded in different body systems are neither equivalent nor interchangeable, but this recognition strengthens the study of stress as always simultaneously cultural and biological, situated in local ecologies, social--political structures, and time.

Background: Aquí Entre Nos (Between Us) is a community-based participatory research project to engage rural, ethno-racially diverse hotel housekeepers in a right to work state during a time of national anti-immigrant policy, wildfires and emergence of a global pandemic. Objectives: We aimed to (1) build trust and social support with the hotel housekeeping community, (2) learn about the occupational health, safety, and workers' rights challenges, strategies, and solutions held by workers, and (3) develop a workforce-driven research and action agenda to improve labor and health conditions. Methods: Participatory mixed methods rooted in popular education are described to form an advisory board and engage the workforce. Lessons Learned: Trusted relationships built through community organizing around immigration, housing, and minimum wage were critical to engage and drive a worker centered research agenda. Conclusions: Despite challenges, housekeeper advisors defined a research agenda that addressed immediate-and long-term needs of the workforce. [ABSTRACT FROM AUTHOR]

BackgroundMarket integration (MI)-increasing production for and consumption from a market-based economy-is drastically altering traditional ways of life and environmental conditions among indigenous Amazonian peoples. The effects of MI on the biology and health of Amazonian children and adolescents, however, remain unclear.AimThis study examines the impact of MI on sub-adult body size and nutritional status at the population, regional and household levels among the Shuar of Amazonian Ecuador.Subjects and methodsAnthropometric data were collected between 2005-2014 from 2164 Shuar (aged 2-19 years) living in two geographic regions differing in general degree of MI. High-resolution household economic, lifestyle and dietary data were collected from a sub-sample of 631 participants. Analyses were performed to investigate relationships between body size and year of data collection, region and specific aspects of household MI.ResultsResults from temporal and regional analyses suggest that MI has a significant and overall positive impact on Shuar body size and nutritional status. However, household-level results exhibit nuanced and heterogeneous specific effects of MI underlying these overarching relationships.ConclusionThis study provides novel insight into the complex socio-ecological pathways linking MI, physical growth and health among the Shuar and other indigenous Amazonian populations.

ObjectivesInformation concerning physical growth among small-scale populations remains limited, yet such data are critical to local health efforts and to foster basic understandings of human life history and variation in childhood development. Using a large dataset and robust modeling methods, this study aims to describe growth from birth to adulthood among the indigenous Shuar of Amazonian Ecuador.MethodsMixed-longitudinal measures of height, weight, and body mass index (BMI) were collected from Shuar participants (n = 2,463; age: 0-29 years). Centile growth curves and tables were created for each anthropometric variable of interest using Generalized Additive Models for Location, Scale, and Shape (GAMLSS). Pseudo-velocity and Lambda-Mu-Sigma curves were generated to further investigate Shuar patterns of growth and to facilitate comparison with United States Center for Disease Control and Prevention and multinational World Health Organization growth references.ResultsThe Shuar are small throughout life and exhibit complex patterns of growth that differ substantially from those of international references. Similar to other Amazonians, Shuar growth in weight compares more favorably to references than growth in height, resulting in BMI curves that approximate international medians. Several additional characteristics of Shuar development are noteworthy, including large observed variation in body size early in life, significant infant growth faltering, extended male growth into adulthood, and a markedly early female pubertal growth spurt in height. Phenotypic plasticity and genetic selection in response to local environmental factors may explain many of these patterns.ConclusionsProviding a detailed reference of growth for the Shuar and other Amazonian populations, this study possesses direct clinical application and affords valuable insight into childhood health and the ecology of human growth.

Objectives Methods Results Conclusions The hypothalamic–pituitary–adrenal (HPA) axis and its primary end product, the glucocorticoid cortisol, are major components of the evolved human stress response. However, most studies have examined these systems among populations in high‐income settings, which differ from the high pathogen and limited resource contexts in which the HPA axis functioned for most of human evolution.We investigated variability in diurnal salivary cortisol patterns among 298 Indigenous Shuar from Amazonian Ecuador (147 males, 151 females; age 2–86 years), focusing on the effects of age, biological sex, and body mass index (BMI) in shaping differences in diurnal cortisol production. Saliva samples were collected three times daily (waking, 30 minutes post‐waking, evening) for three consecutive days to measure key cortisol parameters: levels at waking, the cortisol awakening response, the diurnal slope, and total daily output.Age was positively associated with waking levels and total daily output, with Shuar juveniles and adolescents displaying significantly lower levels than adults (p < .05). Sex was not a significant predictor of cortisol levels (p > .05), as Shuar males and females displayed similar patterns of diurnal cortisol production across the life course. Moreover, age, sex, and BMI significantly interacted to moderate the rate of diurnal cortisol decline (p = .027). Overall, Shuar demonstrated relatively lower cortisol concentrations than high‐income populations.This study expands the documented range of global variation in HPA axis activity and diurnal cortisol production and provides important insights into the plasticity of human stress physiology across diverse developmental and socioecological settings. [ABSTRACT FROM AUTHOR]

BackgroundMarket integration (MI), the suite of social and cultural changes that occur with economic development, has been associated with negative health outcomes such as cardiovascular disease; however, key questions remain about how this transition manifests at the local level.AimThe present paper investigates the effects of MI on health among Shuar, an indigenous lowland Ecuadorian population, with the goal of better understanding the mechanisms responsible for this health transition.Subjects and methodsThis study examines associations between measures of MI and several dimensions of cardiovascular and metabolic health (fasting glucose, lipids [LDL, HDL and total cholesterol; triglycerides] and blood pressure) among 348 adults.ResultsOverall, Shuar males and females have relatively favourable cardiovascular and metabolic health. Shuar who live closer to town have higher total (p < 0.001) and HDL cholesterol (p < 0.001), while Shuar in more remote regions have higher diastolic blood pressure (p = 0.007). HDL cholesterol is positively associated with consumption of market foods (r = 0.140; p = 0.045) and ownership of consumer products (r = 0.184; p = 0.029).ConclusionsThis study provides evidence that MI among Shuar is not a uniformly negative process but instead produces complex cardiovascular and metabolic health outcomes.

UnlabelledMinimal data on bone mineral density changes are available from populations in developing countries. Using calcaneal quantitative ultrasound (QUS) techniques, the current study contributes to remedying this gap in the literature by establishing a normative data set on the indigenous Shuar and non-Shuar Colonos of the Ecuadorian Amazon.PurposeThe paucity of bone mineral density (BMD) data from populations in developing countries partially reflects the lack of diagnostic resources in these areas. Portable QUS techniques now enable researchers to collect bone health data in remote field-based settings and to contribute normative data from developing regions. The main objective of this study is to establish normative QUS data for two Ecuadorian Amazonian populations-the indigenous Shuar and non-Shuar Colonos. The effects of ethnic group, sex, age, and body size on QUS parameters are also considered.MethodsA study cohort consisting of 227 Shuar and 261 Colonos (15-91 years old) were recruited from several small rural Ecuadorian communities in the Upano River Valley. Calcaneal QUS parameters were collected on the right heel of each participant using a Sahara bone sonometer. Three ultrasound generated parameters were employed: broadband ultrasound attenuation (BUA), speed of sound (SOS), and calculated heel BMD (hBMD).ResultsIn both populations and sexes, all QUS values were progressively lower with advancing age. Shuar have significantly higher QUS values than Colonos, with most pronounced differences found between pre-menopausal Shuar and Colono females. Multiple regression analyses show that age is a key predictor of QUS while weight alone is a less consistent determinant. Both Shuar males and females display comparatively greater QUS parameters than other reference populations.ConclusionsThese normative data for three calcaneal QUS parameters will be useful for predicting fracture risk and determining diagnostic QUS criteria of osteoporosis in non-industrialized populations in South America and elsewhere.

ObjectiveMinimal information on physical activity is available for non-Western populations undergoing the transition to a market economy. This is unfortunate given the importance of these data for understanding health issues such as the global obesity epidemic. We consider the utility of using accelerometry technology to examine activity patterns and energy use regulation among indigenous Shuar, an Ecuadorian forager-horticulturalist population undergoing economic and lifestyle change. We investigate sex differences in Shuar activity patterns and the effects of reproductive status on activity. Finally, we discuss the potential of accelerometry use in human biology research.MethodsPhysical activity levels were measured using Actical accelerometers in 49 indigenous Shuar adults (23 males, 26 females) from a rural Ecuadorian community. Female participants were in various reproductive states including pregnant, lactating, and nonpregnant/nonlactating.ResultsActivity counts (AC), activity energy expenditure (AEE), and physical activity levels (PAL) were significantly higher (P < 0.05) in males than females. Significant differences in energy expenditure were found among pregnant or lactating females and males with pregnant or lactating partners (P < 0.001). Males with pregnant or lactating partners also had significantly higher activity levels than did other men (P < 0.01).ConclusionsShuar activity levels are relatively low compared to other non-Western populations. Despite increasing market integration, pregnant and lactating females seem to be adopting a strategy noted in other subsistence populations where male participation in subsistence activities increases to compensate for their partners' elevated reproductive costs. Despite certain limitations, use of accelerometry in human biology research shows promise.

BackgroundThe peak shift model predicts that the age-profile of a pathogen's prevalence depends upon its transmission rate, peaking earlier in populations with higher transmission and declining as partial immunity is acquired. Helminth infections are associated with increased immunoglobulin E (IgE), which may convey partial immunity and influence the peak shift. Although studies have noted peak shifts in helminths, corresponding peak shifts in total IgE have not been investigated, nor has the age-patterning been carefully examined across populations. We test for differences in the age-patterning of IgE between two South American forager-horticulturalist populations and the United States: the Tsimane of Bolivia (n=832), the Shuar of Ecuador (n=289), and the U.S. NHANES (n=8,336). We then examine the relationship between total IgE and helminth prevalences in the Tsimane.Methodology/principal findingsTotal IgE levels were assessed in serum and dried blood spots and age-patterns examined with non-linear regression models. Tsimane had the highest IgE (geometric mean =8,182 IU/ml), followed by Shuar (1,252 IU/ml), and NHANES (52 IU/ml). Consistent with predictions, higher population IgE was associated with steeper increases at early ages and earlier peaks: Tsimane IgE peaked at 7 years, Shuar at 10 years, and NHANES at 17 years. For Tsimane, the age-pattern was compared with fecal helminth prevalences. Overall, 57% had detectable eggs or larva, with hookworm (45.4%) and Ascaris lumbricoides (19.9%) the most prevalent. The peak in total IgE occurred around the peak in A. lumbricoides, which was associated with higher IgE in children

Objective: Cytomegalovirus (CMV) infection is associated with age‐related chronic disease, and co‐infection with Epstein‐Barr virus (EBV) may compound disease risk. We aimed to assess the frequency of CMV infection and its relationship with age among EBV seropositive individuals in an Indigenous Amazonian population. Methods: We report concentrations of CMV and EBV antibodies in dried blood spot samples collected from 157 EBV positive Shuar participants aged 15–86 years (60.5% female) to assess CMV infection rate. We used logistic and linear regression models to examine associations among CMV, EBV, and age, adjusting for sex, geographic region, and body mass index. Results: Nearly two‐thirds (63.1%) of EBV seropositive participants were also CMV seropositive. A 1‐year increase in age was associated with 3.4% higher odds of CMV infection (OR [95% CI]: 1.034 [1.009–1.064], p =.012), but CMV antibody concentration was not significantly associated with age or EBV antibody concentration among co‐infected individuals. Conclusions: Herpesvirus‐related immunosenescence may be important to understanding chronic disease risk among Shuar. Future studies should further explore the role of co‐infection in shaping age‐related changes in immune function. [ABSTRACT FROM AUTHOR]

Objective: Anemia is an important global health challenge. We investigate anemia prevalence among Indigenous Shuar of Ecuador to expand our understanding of population‐level variation, and to test hypotheses about how anemia variation is related to age, sex, and market integration. Methods: Hemoglobin levels were measured in a total sample of 1650 Shuar participants (ages 6 months to 86 years) from 46 communities between 2008 and 2017 to compare anemia prevalence across regions characterized by different levels of market integration. Results: Shuar anemia rates among children under 15 years (12.2%), adult women (10.5%), and adult men (5.3%) were less than half of those previously documented in other neo‐tropical Indigenous populations. Anemia prevalence did not vary between more traditional and market integrated communities (OR = 0.47, p =.52). However, anemia was negatively associated with body mass index (OR = 0.47, p =.002). Conclusions: Compared to other South American Indigenous populations, anemia prevalence is relatively low among Shuar of Ecuador and invariant with market integration. Understanding this pattern can provide valuable insights into anemia prevention among at‐risk populations. [ABSTRACT FROM AUTHOR]

Objectives: This study investigates bone density across the life course among Bolivian Tsimane and Ecuadorian Shuar of Amazonia. Both groups are rural, high‐fertility forager‐horticulturalists, with high lifetime physical activity levels. We test whether Tsimane and Shuar bone density patterns are different from each other, and if both groups are characterized by lower osteoporosis risk compared to U.S. references. Methods: Anthropometric and calcaneal bone density data, obtained via quantitative ultrasonometry (QUS), were collected from 678 Tsimane and 235 Shuar (13–92 years old). Population and sex differences in QUS values (estimated bone mineral density, speed of sound, broadband ultrasound attenuation) by age group were assessed using Mann–Whitney U tests. Age‐related change and age at peak QUS value were determined using polynomial regressions. One‐way analyses of covariance assessed population‐level differences in QUS values by age group adjusting for body mass index. Participants aged 50+ years at elevated osteoporosis risk were identified using a T score < −1.8; binomial tests assessed risk compared to U.S. references. Results: Shuar males and females <50 years old have QUS values 3–36% higher than Tsimane, with differences evident in adolescence. Among Tsimane and Shuar, 49 and 23% of participants aged 50+ years old, respectively, are at high risk for osteoporosis, compared to 34% of Americans; Shuar osteoporosis risk is comparable to Americans, while Tsimane risk is elevated. Conclusions: Disparate patterns in QUS values are documented for Tsimane and Shuar, with pronounced differences early in life. Potential explanations for differences include gene–environment interactions and/or degree of market integration, which influences diet, activity profiles, pathogen exposures, and other lifestyle covariates. As Tsimane osteoporosis risk is greater than in the United States, findings point to alternative risk factors for low bone density that are not readily discernible in industrialized populations. [ABSTRACT FROM AUTHOR]

Objectives Perceived income adequacy is positively associated with self-rated health (SRH) and quality of life (QOL) among adults in higher-income countries. Additionally, older individuals often report higher levels of income adequacy. However, it is unclear if these associations, documented primarily in high-income countries, are also evident across economically and culturally distinctive low- and middle-income countries. Methods Data were drawn from the World Health Organization's Study on global AGEing and adult health (SAGE), a study of adults aged 50 years or older in China, Ghana, India, Mexico, the Russian Federation, and South Africa. Smaller samples of younger adults (18–49 years) were included for comparison purposes. Participants reported income adequacy, SRH, and QOL. Associations between age and income adequacy and between income adequacy and SRH/QOL were examined using country-specific logistic regression analysis. Results Older adults in China and Russia were more likely to report better income adequacy than their 18- to 49-year-old counterparts; however, the opposite was observed in Ghana and India. SRH and QOL improved as income adequacy increased in all countries. Discussion As expected, income adequacy was correlated with SRH and QOL. However, the relationship between age and income adequacy varied cross-culturally, potentially due to differences in familial and governmental financial support. [ABSTRACT FROM AUTHOR]

The hypothalamic-pituitary-adrenal (HPA) axis represents an important and evolutionarily ancient biological pathway linking physical and psychological stressors with human health. Despite considerable research exploring the physiological stress response among developed populations, few studies have examined HPA activity in non-industrialized contexts, restricting understanding of variation in human stress reactivity across global socio-ecological diversity. The present study addresses this shortcoming by investigating diurnal cortisol rhythms among Garisakang forager-horticulturalists of remote, lowland Papua New Guinea. Using a large sample of repeated salivary cortisol measurements from 169 participants (age 4-70 years), multilevel growth curve models were constructed to assess Garisakang waking cortisol concentrations and diurnal cortisol slopes. As predicted, results demonstrate identifiable but substantially diminished diurnal cortisol rhythms relative to those of industrialized populations. Sample-wide, Garisakang cortisol concentrations are highest upon waking (mean = 4.86 nmol/L) and decrease throughout the day at a mean rate of only −0.18 nmol/L/h or −6.20%/h. Age and sex significantly predict evaluated cortisol parameters in ways not consistently reported among industrialized populations, suggesting that Garisakang diurnal cortisol rhythms are defined by distinct ontogenetic trajectories across the lifespan. These findings highlight cross-cultural diversity in HPA activity and have important implications for understanding basic mechanisms of the physiological stress response in contexts of chronic physical stressors such as limited nutrition, heavy burden of infectious disease, and high levels of physical activity. [ABSTRACT FROM AUTHOR]