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1. Soil‐transmitted helminth infection and intestinal inflammation among the Shuar of Amazonian Ecuador

   https://doi.org/10.1002/ajpa.23897  

   Cepon‐Robins, Tara J. ; Gildner, Theresa E. ; Schrock, Joshua ; Eick, Geeta ; Bedbury, Ali ; Liebert, Melissa A. ; Urlacher, Samuel S. ; Madimenos, Felicia C. ; Harrington, Christopher J. ; Amir, Dorsa ; et al ( July 2019 , American Journal of Physical Anthropology)

   Little research exists documenting levels of intestinal inflammation among indigenous populations where exposure to macroparasites, like soil‐transmitted helminths (STHs), is common. Reduced STH exposure is hypothesized to contribute to increased prevalence of elevated intestinal inflammation in wealthy nations, likely due to coevolutionary histories between STHs and human immune systems that favored anti‐inflammatory pathways. Here, we document levels of intestinal inflammation and test associations with STH infection among the Shuar of Ecuador, an indigenous population undergoing socioeconomic/lifestyle changes that influence their hygienic environment. We predict that fecal calprotectin (FC; a measure of intestinal inflammation) will be lower in STH infected individuals and that FC will be negatively associated with infection intensity.

   Stool samples to analyze FC levels and STH infection were collected from 69 Shuar participants (ages 5–75 years). Children (<15 years) and adults (15+ years) were analyzed separately to understand the role of exposure in immune system development and the intestinal inflammatory response.

   Two species of STH were present:Ascaris lumbricoidesandTrichuris trichiura. The relationships between infection and intestinal inflammation were age‐ and species‐specific. While no significant relationships were found among adults, children who were singly infected withT. trichiurahad lower FC levels than uninfected children. Infection intensity was not significantly associated with FC in children or adults.

   These preliminary results provide limited support for our hypotheses, documenting tentative age‐ and species‐specific associations between FC and infection status. Findings may point to the importance of species‐specific STH exposure during immune system development.

    

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2. Disparities in bone density across contemporary Amazonian forager‐horticulturalists: Cross‐population comparison of the Tsimane and Shuar

   https://doi.org/10.1002/ajpa.23949  

   Madimenos, Felicia C. ; Liebert, Melissa A. ; Cepon‐Robins, Tara J. ; Urlacher, Samuel S. ; Josh Snodgrass, J. ; Sugiyama, Lawrence S. ; Stieglitz, Jonathan ( October 2019 , American Journal of Physical Anthropology)

   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.

   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–WhitneyUtests. 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 aTscore < −1.8; binomial tests assessed risk compared to U.S. references.

   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.

   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.

    

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3. High energy requirements and water throughput of adult Shuar forager‐horticulturalists of Amazonian Ecuador

   https://doi.org/10.1002/ajhb.23223  

   Christopher, Lauren ; Madimenos, Felicia C. ; Bribiescas, Richard G. ; Urlacher, Samuel S. ; Snodgrass, James J. ; Sugiyama, Lawrence S. ; Pontzer, Herman ( February 2019 , American Journal of Human Biology)

   We measured total energy expenditure (TEE; kcal/d) and water throughput (L/d) among Shuar forager‐horticulturalists from Amazonian Ecuador to compare their daily energy and water demands to adults in other small‐scale and industrialized populations.

   TEE and water throughput were measured using the doubly labeled water method among 15 Shuar adults (eight women, seven men; age range 18‐60 years) living in a relatively remote village. We used multiple regression to assess the effects of anthropometric variables (body size, fat free mass, age, and sex) on TEE and water throughput. We also compared Shuar TEE and water throughput to those of other small‐scale and industrialized societies.

   TEE among Shuar adults (men: 4141 ± 645 kcal/d, women: 2536 ± 281 kcal/d) was most strongly correlated with fat free mass. Estimated physical activity levels (PAL) calculated as (TEE/estimated BMR), were greater for men (2.34 ± 0.29) than women (1.83 ± 0.14,P < 0.001). Water throughput was also greater among Shuar men (9.37 ± 2.34 L/d) than women (4.76 ± 0.36 L/d,P < 0.001). Shuar TEE and water throughput were elevated compared to adults in industrialized populations.

   TEE and PAL of Shuar men are among the highest recorded during normal daily life, and likely reflect both high levels of physical activity and cultural dietary practices. Drinking large amounts of chicha, a traditional carbohydrate‐rich drink made from manioc, likely contributes to the high levels of water throughput among Shuar men, and may contribute to elevated TEE.

    

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4. Pathogen disgust sensitivity protects against infection in a high pathogen environment

   https://doi.org/10.1073/pnas.2018552118  

   Cepon-Robins, Tara J. ; Blackwell, Aaron D. ; Gildner, Theresa E. ; Liebert, Melissa A. ; Urlacher, Samuel S. ; Madimenos, Felicia C. ; Eick, Geeta N. ; Snodgrass, J. Josh ; Sugiyama, Lawrence S. ( February 2021 , Proceedings of the National Academy of Sciences)

   Disgust is hypothesized to be an evolved emotion that functions to regulate the avoidance of pathogen-related stimuli and behaviors. Individuals with higher pathogen disgust sensitivity (PDS) are predicted to be exposed to and thus infected by fewer pathogens, though no studies have tested this directly. Furthermore, PDS is hypothesized to be locally calibrated to the types of pathogens normally encountered and the fitness-related costs and benefits of infection and avoidance. Market integration (the degree of production for and consumption from market-based economies) influences the relative costs/benefits of pathogen exposure and avoidance through sanitation, hygiene, and lifestyle changes, and is thus predicted to affect PDS. Here, we examine the function of PDS in disease avoidance, its environmental calibration, and its socioecological variation by examining associations among PDS, market-related lifestyle factors, and measures of bacterial, viral, and macroparasitic infection at the individual, household, and community levels. Data were collected among 75 participants (ages 5 to 59 y) from 28 households in three Ecuadorian Shuar communities characterized by subsistence-based lifestyles and high pathogen burden, but experiencing rapid market integration. As predicted, we found strong negative associations between PDS and biomarkers of immune response to viral/bacterial infection, and weaker associations between PDS and measures of macroparasite infection, apparently mediated by market integration-related differences. We provide support for the previously untested hypothesis that PDS is negatively associated with infection, and document variation in PDS indicative of calibration to local socioeconomic conditions. More broadly, findings highlight the importance of evolved psychological mechanisms in human health outcomes.

    

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5. The effects of lifestyle change on indicators of cardiometabolic health in semi-nomadic pastoralists

   https://doi.org/10.1093/emph/eoad030  

   Swanson, Zane S. ; Bethancourt, Hilary ; Nzunza, Rosemary ; Ndiema, Emmanuel ; Braun, David R. ; Rosinger, Asher Y. ; Pontzer, Herman ( September 2023 , Evolution, Medicine, and Public Health)

   Non-communicable disease risk and the epidemic of cardiometabolic diseases continue to grow across the expanding industrialized world. Probing the relationships between evolved human physiology and modern socioecological conditions is central to understanding this health crisis. Therefore, we investigated the relationships between increased market access, shifting subsistence patterns and cardiometabolic health indicators within Daasanach semi-nomadic pastoralists who vary in their engagement in traditional lifestyle and emerging market behaviors.

   We conducted cross-sectional socioecological, demographic and lifestyle stressor surveys along with health, biomarker and nutrition examinations among 225 (51.6% female) Daasanach adults in 2019–2020. We used linear mixed-effects models to test how differing levels of engagement in market integration and traditional subsistence activities related to blood pressure (BP), body composition and blood chemistry.

   We found that systolic and diastolic BP, as well as the probability of having high BP (hypertension), were negatively associated with distance to market, a proxy for market integration. Additionally, body composition varied significantly by socioeconomic status (SES), with significant positive associations between BMI and body fat and higher SES among adults.

   While evidence for evolutionary mismatch and health variation have been found across a number of populations affected by an urban/rural divide, these results demonstrate the effects of market integration and sedentarization on cardiometabolic health associated with the early stages of lifestyle changes. Our findings provide evidence for the changes in health when small-scale populations begin the processes of sedentarization and market integration that result from myriad market pressures.

    

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