Biological and Physical Anthropology Commons^™

Associations Between Male Testosterone And Immune Function In A Pathogenically Stressed Forager-Horticultural Population, Benjamin C. Trumble, Aaron D. Blackwell, Jonathan Stieglitz, Melissa Emery Thompson, Ivan Maldonado Suarez, Hillard Kaplan, Michael Gurven

ESI Publications

Objectives—Despite well-known fitness advantages to males who produce and maintain high endogenous testosterone levels, such phenotypes may be costly if testosterone-mediated investment in reproductive effort trade-off against investment in somatic maintenance. Previous studies of androgen-mediated trade-offs in human immune function find mixed results, in part because most studies either focus on a few indicators of immunity, are confounded by phenotypic correlation, or are observational. Here the association between male endogenous testosterone and 13 circulating cytokines are examined before and after ex vivo antigen stimulation with phytohaemagglutinin (PHA) and lipopolysaccharides (LPS) in a high pathogen population of Bolivian forager-horticulturalists.

Materials …

Health Costs Of Reproduction Are Minimal Despite High Fertility, Mortality And Subsistence Lifestyle, Michael Gurven, Megan Costa, Ben Trumble, Jonathan Stieglitz, Bret Beheim, Daniel Eid Rodriguez, Paul L. Hooper, Hillard Kaplan

ESI Publications

Women exhibit greater morbidity than men despite higher life expectancy. An evolutionary life history framework predicts that energy invested in reproduction trades-off against investments in maintenance and survival. Direct costs of reproduction may therefore contribute to higher morbidity, especially for women given their greater direct energetic contributions to reproduction. We explore multiple indicators of somatic condition among Tsimane forager-horticulturalist women (Total Fertility Rate = 9.1; n = 592 aged 15–44 years, n = 277 aged 45+). We test whether cumulative live births and the pace of reproduction are associated with nutritional status and immune function using longitudinal data spanning 10 …

High Resting Metabolic Rate Among Amazonian Forager-Horticulturalists Experiencing High Pathogen Burden, Michael Gurven, Benjamin C. Trumble, Jonathan Stieglitz, Gandhi Yetish, Daniel Cummings, Aaron D. Blackwell, Bret Beheim, Hillard Kaplan, Herman Pontzer

ESI Publications

Objectives—Resting metabolic rate (RMR) reflects energetic costs of homeostasis and accounts for 60-75% of total energy expenditure (TEE). Lean mass and physical activity account for much RMR variability, but the impact of prolonged immune activation from infection on human RMR is unclear in naturalistic settings. We evaluate the effects of infection on mass-corrected RMR among Bolivian forager-horticulturalists, and assess whether RMR declines more slowly with age than in hygienic sedentary populations, as might be expected if older adults experience high pathogen burden.

Materials and Methods—RMR was measured by indirect calorimetry (Fitmate MED, Cosmed) in 1,300 adults aged 20-90 …

Immune Function In Amazonian Horticulturalists, Aaron D. Blackwell, Benjamin C. Trumble, Ivan Maldonado Suarez, Jonathan Stieglitz, Bret Beheim, J. Josh Snodgrass, Hillard Kaplan, Michael Gurven

ESI Publications

Background—Amazonian populations are exposed to diverse parasites and pathogens, including protozoal, bacterial, fungal, and helminthic infections. Yet much of our understanding of the immune system is based on industrialised populations where these infections are relatively rare.

Aim—We examine distributions and age-related differences in 22 measures of immune function for Bolivian forager-horticulturalists and US and European populations.

Subjects and Methods—Subjects were 6,338 Tsimane aged 0–90 years. Blood samples collected between 2004–2014 were analysed for 5-part blood differentials, C-reactive protein, erythrocyte sedimentation rate (ESR), and total immunoglobulins E, G, A, and M. Flow cytometry was used to quantify naive …

Helminth Infection, Fecundity, And Age Of First Pregnancy In Women, Aaron D. Blackwell, Marilyne D. Tamayo, Bret Beheim, Benjamin C. Trumble, Jonathan Stieglitz, Paul L. Hooper, Melanie Martin, Hillard Kaplan, Michael Gurven

ESI Publications

Infection with intestinal helminths results in immunological changes that influence the odds of comorbid infections, and might also affect fecundity by inducing immunological states supportive of conception and pregnancy. Here we investigate associations between intestinal helminths and fertility in human females, utilizing nine years of longitudinal data from 986 Bolivian forger-horticulturalists, experiencing natural fertility and a 70% helminth prevalence. We find that different species of helminth are associated with opposing effects on fecundity. Infection with roundworm (Ascaris lumbricoides) is associated with earlier first births and shortened interbirth intervals, while infection with hookworm is associated with delayed first pregnancy and extended …

Natural Sleep And Its Seasonal Variations In Three Pre-Industrial Societies, Gandhi Yetish, Hillard Kaplan, Michael Gurven, Brian Wood, Herman Pontzer, Paul R. Manger, Charles Wilson, Ronald Mcgregor, Jerome M. Siegel

ESI Publications

How did humans sleep before the modern era? Because the tools to measure sleep under natural conditions were developed long after the invention of the electric devices suspected of delaying and reducing sleep, we investigated sleep in three preindustrial societies[1–3]. We find that all three show similar sleep organization, suggesting that they express core human sleep patterns, likely characteristic of pre-modern era Homo sapiens. Sleep periods, the times from onset to offset, averaged 6.9–8.5-h, with sleep durations of 5.7–7.1-h, amounts near the low end of those industrial societies[4–7]. There was a difference of nearly 1-h between summer and winter sleep. …

Calcaneal Quantitative Ultrasound Indicates Reduced Bone Status Among Physically Active Adult Forager-Horticulturalists, Jonathan Stieglitz, Felicia C. Madimenos, Hillard Kaplan, Michael Gurven

ESI Publications

Six months of exclusive breastfeeding (EBF) is considered optimal for infant health, though globally most infants begin complementary feeding (CF) earlier—including among populations that practice prolonged breastfeeding. Two frameworks for understanding patterns of early CF emerge in the literature. In the first, maternal and infant needs trade-off, as “maternal-centric” factors—related to time and energy demands, reproductive investment, cultural influences, and structural barriers— favor supplanting breastfeeding with earlier and increased CF. A second framework considers that “infant-centric” factors—related to infant energetic needs—favor CF before six months to supplement breastfeeding.

We apply these two frameworks in examining early CF among the Tsimane—a …

Does Market Integration Buffer Risk, Erode Traditional Sharing Practices And Increase Inequality? A Test Among Bolivian Forager-Farmers, Michael Gurven, Adrian V. Jaeggi, Christopher Von Rueden, Paul L. Hooper, Hillard Kaplan

ESI Publications

Sharing and exchange are common practices for minimizing food insecurity in rural populations. The advent of markets and monetization in egalitarian indigenous populations presents an alternative means of managing risk, with the potential impact of eroding traditional networks. We test whether market involvement buffers several types of risk and reduces traditional sharing behavior among Tsimane Amerindians of the Bolivian Amazon. Results vary based on type of market integration and scale of analysis (household vs. village), consistent with the notion that local culture and ecology shape risk management strategies. Greater wealth and income were unassociated with the reliance on others for …

Depression As Sickness Behavior? A Test Of The Host Defense Hypothesis In A High Pathogen Population, Jonathan Stieglitz, Benjamin C. Trumble, Melissa Emery Thompson, Aaron D. Blackwell, Hillard Kaplan, Michael Gurven

ESI Publications

Sadness is an emotion universally recognized across cultures, suggesting it plays an important functional role in regulating human behavior. Numerous adaptive explanations of persistent sadness interfering with daily functioning (hereafter “depression”) have been proposed, but most do not explain frequent bidirectional associations between depression and greater immune activation. Here we test several predictions of the host defense hypothesis, which posits that depression is part of a broader coordinated evolved response to infection or tissue injury (i.e. “sickness behavior”) that promotes energy conservation and reallocation to facilitate immune activation. In a high pathogen population of lean and relatively egalitarian Bolivian foragerhorticulturalists, …

Inclusive Fitness And Differential Productivity Across The Life Course Determine Intergenerational Transfers In A Small-Scale Human Society, Paul L. Hooper, Michael Gurven, Jeffrey Winking, Hillard Kaplan

ESI Publications

Transfers of resources between generations are an essential element in current models of human life-history evolution accounting for prolonged development, extended lifespan and menopause. Integrating these models with Hamilton’s theory of inclusive fitness, we predict that the interaction of biological kinship with the age-schedule of resource production should be a key driver of intergenerational transfers. In the empirical case of Tsimane’ forager–horticulturalists in Bolivian Amazonia, we provide a detailed characterization of net transfers of food according to age, sex, kinship and the net need of donors and recipients. We show that parents, grandparents and siblings provide significant net downward transfers …

Low Mineral Density Of A Weight-Bearing Bone Among Adult Women In A High Fertility Population, Jonathan Stieglitz, Bret Beheim, Benjamin C. Trumble, Felicia C. Madimenos, Hillard Kaplan, Michael Gurven

ESI Publications

Evolutionary theories of aging posit that greater reproductive effort causes somatic decline given a fundamental trade-off between investing energy in reproduction and repair. Few studies in high fertility human populations support this hypothesis, and problems of phenotypic correlation can obscure the expected trade-off between reproduction and somatic condition. This cross-sectional study investigates whether greater reproductive effort is associated with reduced calcaneal bone mineral density (BMD) among female Tsimane forager-farmers of lowland Bolivia. We also investigate whether female Tsimane BMD values are lower than sex- and age-matched US reference values, despite the fact that Tsimane engage in higher physical activity levels …

Leadership In An Egalitarian Society, Christopher Von Rueden, Michael Gurven, Hillard Kaplan, Jonathan Stieglitz

ESI Publications

Leadership is instrumental to resolution of collective action dilemmas, particularly in large, heterogeneous groups. Less is known about the characteristics or effectiveness of leadership in small-scale, homogeneous, and relatively egalitarian societies, in which humans have spent most of our existence. Among Tsimane’ forager-horticulturalists of Bolivia, we (1) assess traits of elected leaders under experimental and naturalistic conditions and (2) test whether leaders impact collective action outcomes. We find that elected leaders are physically strong and have more kin and other exchange partners. Their ranks on physical dominance, kin support, and trustworthiness predict how well their groups perform, but only where …

Political Influence Associates With Cortisol And Health Among Egalitarian Forager-Farmers, Christopher Von Rueden, Benjamin C. Trumble, Melissa Emery Thompson, Jonathan Stieglitz, Paul L. Hooper, Aaron D. Blackwell, Hillard Kaplan, Michael Gurven

ESI Publications

Background and objectives: Low social status increases risk of disease due, in part, to the psychosocial stress that accompanies feeling subordinate or poor. Previous studies report that chronic stress and chronically elevated cortisol can impair cardiovascular and immune function. We test whether lower status is more benign in small-scale, relatively egalitarian societies, where leaders lack coercive authority and there is minimal material wealth to contest.

Methodology: Among Tsimane’ forager-horticulturalists of lowland Bolivia, we compare informal political influence among men with urinary cortisol, immune activation (innate and acquired), and morbidity as assessed during routine medical exams.

Results: After …

Atherosclerosis: A Longue Durée Approach, L. Samuel Wann, Randall C. Thompson, Adel H. Allam, Caleb E. Finch, Albert Zink, Hillard Kaplan, Bruno Frohlich, Guido P. Lombardi, M. Linda Sutherland, James D. Sutherland, Lucia Watson, Samantha L. Cox, Michael I. Miyamoto, Alexandre F. R. Stewart, Jagat Narula, Gregory S. Thomas

ESI Publications

Fernand Braudel popularized the longue durée approach to scholarly investigation in the mid-20th century. The longue durée approach can be loosely translated to mean “look for the big picture, synthesize data collected using all available methodology over the long periods of time to identify fundamental principles, rather than becoming preoccupied with isolated observations.” Braudel, a historian and economist, emphasized observation of enduring historical structures and analysis of long-term, panoramic economic trends rather than concentrating on detailed descriptions of particular events or individuals. He also urged the use of insight gained from many scholarly disciplines to identify the essential underpinnings of …

Genomic Correlates Of Atherosclerosis In Ancient Humans, Albert Zink, L. Samuel Wann, Randall C. Thompson, Andreas Keller, Frank Maixner, Adel H. Allam, Caleb E. Finch, Bruno Frohlich, Hillard Kaplan, Guido P. Lombardi, M. Linda Sutherland, James D. Sutherland, Lucia Watson, Samantha L. Cox, Michael I. Miyamoto, Jagat Narula, Alexandre F. R. Stewart, Gregory S. Thomas, Johannes Krause

ESI Publications

Paleogenetics offers a unique opportunity to study human evolution, population dynamics, and disease evolution in situ. Although histologic and computed x-ray tomographic investigations of ancient mummies have clearly shown that atherosclerosis has been present in humans for more than 5,000 years, limited data are available on the presence of genetic predisposition for cardiovascular disease in ancient human populations. In a previous whole-genome study of the Tyrolean Iceman, a 5,300-year-old glacier mummy from the Alps, an increased risk for coronary heart disease was detected. The Iceman’s genome revealed several single nucleotide polymorphisms that are linked with cardiovascular disease in genome-wide association …

Why Did Ancient People Have Atherosclerosis?: From Autopsies To Computed Tomography To Potential Causes, Gregory S. Thomas, L. Samuel Wann, Adel H. Allam, Randall C. Thompson, David E. Michalik, M. Linda Sutherland, James D. Sutherland, Guido P. Lombardi, Lucia Watson, Samantha L. Cox, Clide M. Valladolid, Gomaa Abd El-Maksoud, Muhammad Al-Tohamy Soliman, Ibrahem Badr, Abd El-Halim Nur El-Din, Emily M. Clarke, Ian G. Thomas, Michael I. Miyamoto, Hillard Kaplan, Bruno Frohlich, Jagat Narula, Alexandre F. R. Stewart, Albert Zink, Caleb E. Finch

ESI Publications

Computed tomographic findings of atherosclerosis in the ancient cultures of Egypt, Peru, the American Southwest and the Aleutian Islands challenge our understanding of the fundamental causes of atherosclerosis. Could these findings be true? Is so, what traditional risk factors might be present in these cultures that could explain this apparent paradox? The recent computed tomographic findings are consistent with multiple autopsy studies dating as far back as 1852 that demonstrate calcific atherosclerosis in ancient Egyptians and Peruvians. A nontraditional cause of atherosclerosis that could explain this burden of atherosclerosis is the microbial and parasitic inflammatory burden likely to be present …

Funerary Artifacts, Social Status, And Atherosclerosis In Ancient Peruvian Mummy Bundles, M. Linda Sutherland, Samantha L. Cox, Guido P. Lombardi, Lucia Watson, Clide M. Valladolid, Caleb E. Finch, Albert Zink, Bruno Frohlich, Hillard Kaplan, David E. Michalik, Michael I. Miyamoto, Adel H. Allam, Randall C. Thompson, L. Samuel Wann, Jagat Narula, Gregory S. Thomas, James D. Sutherland

ESI Publications

Background: Evidence of atherosclerotic plaques in ancient populations has led to the reconsideration of risk factors for heart disease and of the common belief that it is a disease of modern times.

Methods: Fifty-one wrapped mummy bundles excavated from the sites of Huallamarca, Pedreros, and Rinconada La Molina from the Puruchuco Museum collection in Lima, Peru, were scanned using computed tomography to investigate the presence of atherosclerosis. Funerary artifacts contained within the undisturbed mummy bundles were analyzed as an attempt to infer the social status of the individuals to correlate social status with evidence of heart disease in …

The Evolutionary Fitness Of Personality Traits In A Small-Scale Subsistence Society, Michael Gurven, Christopher Von Rueden, Jonathan Stieglitz, Hillard Kaplan, Daniel Eid Rodriguez

ESI Publications

"Personality, or “behavioral syndromes”, are relatively stable dispositional traits and behaviors that have now been identified in a myriad of social species (Gosling, 2001; Sih et al., 2004), and with clear consequences on fitness (Smith & Blumstein, 2008). The canalization of personality during development and relative stability thereafter, despite varying circumstances over the life course that might otherwise favor greater plasticity, is an important problem attracting much theoretical and empirical attention (Dall et al., 2004; Dingemanse et al., 2010). Further, personality is highly heritable, yet how heritable genetic variation in personality traits is maintained over generations remains another conundrum (Buss …

Dynamical Structure Of A Traditional Amazonian Social Network, Paul L. Hooper, Simon Dedeo, Ann E. Caldwell Hooper, Michael Gurven, Hillard Kaplan

ESI Publications

Reciprocity is a vital feature of social networks, but relatively little is known about its temporal structure or the mechanisms underlying its persistence in real world behavior. In pursuit of these two questions, we study the stationary and dynamical signals of reciprocity in a network of manioc beer (Spanish: chicha; Tsimane’: shocdye’) drinking events in a Tsimane’ village in lowland Bolivia. At the stationary level, our analysis reveals that social exchange within the community is heterogeneously patterned according to kinship and spatial proximity. A positive relationship between the frequencies at which two families host each other, controlling for kinship and …

Patterns Of Senescence In Human Cardiovascular Fitness: Vo2 Max In Subsistence And Industrialized Populations, Anne C. Pisor, Michael Gurven, Aaron D. Blackwell, Hillard Kaplan, Gandhi Yetish

ESI Publications

Objectives—This study explores whether cardiovascular fitness levels and senescent decline are similar in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane, we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized populations.

Methods—Maximal oxygen uptake (VO2max) was estimated using a step test heart rate method for 701 participants. We compared these estimates …

Age-Independent Increases In Male Salivary Testosterone During Horticultural Activity Among Tsimane Forager-Farmers, Benjamin C. Trumble, Daniel K. Cummings, Kathleen A. O'Connor, Darryl J. Holman, Eric A. Smith, Hillard Kaplan, Michael D. Gurven

ESI Publications

Testosterone plays an important role in mediating male reproductive trade-offs in many vertebrate species, augmenting muscle and influencing behavior necessary for male-male competition and mating-effort. Among humans, testosterone may also play a key role in facilitating male provisioning of offspring as muscular and neuromuscular performance are deeply influenced by acute changes in testosterone. This study examines acute changes in salivary testosterone among 63 Tsimane men ranging in age from 16–80 (mean 38.2) years during one-hour bouts of treechopping while clearing horticultural plots. The Tsimane forager-horticulturalists living in the Bolivian Amazon experience high energy expenditure associated with food production, have high …

Household Task Delegation Among High-Fertility Forager-Horticulturalists Of Lowland Bolivia, Jonathan Stieglitz, Michael Gurven, Hillard Kaplan, Paul L. Hooper

ESI Publications

Human kin cooperation is universal, leading researchers to label humans as “cooperative breeders.” Despite widespread interest in human cooperation, there has been no systematic study of how household economic decision making occurs. We document age and sex profiles of task delegation by parents to children ages 4–18 among Bolivian forager-horticulturalists. We test for sex differences in the probability of delegation and examine whether tasks are more likely delegated as household labor demand increases. We also test whether food acquisition tasks are more likely delegated to higher producers.We find mixed support for the prediction that girls are more likely delegated domestic …

Physical Activity And Modernization Among Bolivian Amerindians, Michael Gurven, Adrian V. Jaeggi, Hillard Kaplan, Daniel Cummings

ESI Publications

Background: Physical inactivity is a growing public health problem, and the fourth leading risk factor for global mortality. Conversely, indigenous populations living traditional lifestyles reportedly engage in vigorous daily activity that is protective against non-communicable diseases. Here we analyze physical activity patterns among the Tsimane, forager-horticulturalists of Amazonian Bolivia with minimal heart disease and diabetes. We assess age patterns of adult activity among men and women, test whether modernization affects activity levels, and examine whether nascent obesity is associated with reduced activity.

Methods and Findings: A factorial method based on a large sample of behavioral observations was employed …

How Universal Is The Big Five? Testing The Five-Factor Model Of Personality Variation Among Forager-Farmers In The Bolivian Amazon, Michael Gurven, Christopher Von Rueden, Maxim Massenkoff, Hillard Kaplan, Marino Lero Vie

ESI Publications

The five-factor model (FFM) of personality variation has been replicated across a range of human societies, suggesting the FFM is a human universal. However, most studies of the FFM have been restricted to literate, urban populations, which are uncharacteristic of the majority of human evolutionary history. We present the first test of the FFM in a largely illiterate, indigenous society. Tsimane forager–horticulturalist men and women of Bolivia (n = 632) completed a translation of the 44-item Big Five Inventory (Benet-Martínez & John, 1998), a widely used metric of the FFM. We failed to find robust support for the FFM, based …

Modernization, Sexual Risk-Taking, And Gynecological Morbidity Among Bolivian Forager-Horticulturalists, Jonathan Stieglitz, Aaron D. Blackwell, Raúl Quispe Gutierrez, Edhitt Cortez Linares, Michael Gurven, Hillard Kaplan

ESI Publications

Sexual risk-taking and reproductive morbidity are common among rapidly modernizing populations with little material wealth, limited schooling, minimal access to modern contraception and healthcare, and gendered inequalities in resource access that limit female autonomy in cohabiting relationships. Few studies have examined how modernization influences sexual risk-taking and reproductive health early in demographic transition. Tsimane are a natural fertility population of Bolivian forager-farmers; they are not urbanized, reside in small-scale villages, and lack public health infrastructure. We test whether modernization is associated with greater sexual risk-taking, report prevalence of gynecological morbidity (GM), and test whether modernization, sexual risk-taking and parity are …

Why Do Women Have More Children Than They Want? Understanding Differences In Women's Ideal And Actual Family Size In A Natural Fertility Population, Lisa Mcallister, Michael Gurven, Hillard Kaplan, Jonathan Stieglitz

ESI Publications

Objectives—We develop and test a conceptual model of factors influencing women’s ideal family size (IFS) in a natural fertility population, the Tsimane of Bolivia. The model posits affects of socioecology, reproductive history, maternal condition, and men’s IFS. We test three hypotheses for why women may exceed their IFS despite experiencing socioeconomic development: (H1) limited autonomy; (H2) improved maternal condition; and (H3) low returns on investments in embodied capital.

Methods—Women’s reproductive histories and prospective fertility data were collected from 2002 to 2008 (n = 305 women). Semistructured interviews were conducted with Tsimane women to study the perceived value of …

Fatty Acid Composition In The Mature Milk Of Bolivian Forager-Horticulturalists: Controlled Comparisons With A Us Sample, Melanie A. Martin, William D. Lassek, Steven J. C. Gaulin, Rhobert W. Evans, Sheela S. Geraghty, Barbara S. Davidson, Ardythe L. Morrow, Hillard Kaplan, Michael Gurven

ESI Publications

Breast milk fatty acid (FA) composition varies greatly among individual women, including in percentages of the long-chain polyunsaturated FAs (LCPUFA) 20:4n-6 (arachidonic acid, AA) and 22:6n-3 (docosahexaenoic acid, DHA), which are important for infant neurological development. It has been suggested that owing to wide variation in milk LCPUFA and low DHA in Western diets, standards of milk FA composition should be derived from populations consuming traditional diets. We collected breast milk samples from Tsimane women at varying lactational stages (6–82 weeks). The Tsimane are an indigenous, natural fertility, subsistence-level population living in Amazonia Bolivia. Tsimane samples were matched by lactational …

From The Womb To The Tomb: The Role Of Transfers In Shaping The Evolved Human Life History, Michael Gurven, Jonathan Stieglitz, Paul L. Hooper, Cristina Gomes, Hillard Kaplan

ESI Publications

Humans are the longest living and slowest growing of all primates. Although most primates are social, humans are highly cooperative and social in ways that likely co-evolved with the slow human life history. In this paper we highlight the role of resource transfers and non-material assistance within and across generations in shaping low human mortality rates. The use of complex cooperative strategies to minimize risk is a necessary precursor for selecting further reductions in mortality rate in late adulthood. In conjunction with changes in the age-profile of production, the impacts of resource transfers and other forms of cooperation on reducing …

Infidelity, Jealousy, And Wife Abuse Among Tsimane Forager-Farmers: Testing Evolutionary Hypotheses Of Marital Conflict, Jonathan Stieglitz, Michael Gurven, Hillard Kaplan, Jeffrey Winking

ESI Publications

What causes marital conflict, and which marital conflicts are more likely to result in men’s violence against their wives? It has long been argued that men’s jealousy over women’s infidelity is the strongest impetus to men’s lethal and non-lethal violence against female partners. Less is known about the extent to which women’s jealousy over men’s infidelity precipitates men’s violence against female partners. Husbands are more likely than wives to commit infidelity, and men and women report a similar frequency and intensity of jealous emotions during recalls of potential infidelity. If men are likely to use time and resources for pursuit …

Evidence For A Peak Shift In A Humoral Response To Helminths: Age Profiles Of Ige In The Shuar Of Ecuador, The Tsimane Of Bolivia, And The U.S. Nhanes, Aaron D. Blackwell, Michael D. Gurven, Lawrence S. Sugiyama, Felicia C. Madimenos, Melissa A. Liebert, Melanie A. Martin, Hillard Kaplan, J. Josh Snodgrass

ESI Publications

Background: The 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 agepatterning of IgE between two South American forager-horticulturalist populations and the United States: the Tsimane …