Other Economics Commons^™

Horticultural Activity Predicts Later Localized Limb Status In A Contemporary Pre-Industrial Population, Jonathan Stieglitz, Benjamin C. Trumble, Hillard Kaplan, Michael Gurven

ESI Publications

Objectives—Modern humans may have gracile skeletons due to low physical activity levels and mechanical loading. Tests using prehistoric skeletons are limited by the inability to assess behaviour directly, while modern industrialized societies possess few socio-ecological features typical of human evolutionary history. Among Tsimane forager-horticulturalists, we test whether greater activity levels and, thus, increased loading earlier in life are associated with greater later-life bone status and diminished age-related bone loss.

Materials and Methods—We used quantitative ultrasonography to assess radial and tibial status among adults aged 20+ years (mean±SD age=49±15; 52% female). We conducted systematic behavioural observations to assess earlier-life …

Human Grooming In Comparative Perspective: People In Six Small-Scale Societies Groom Less But Socialize Just As Much As Expected For A Typical Primate, Adrian V. Jaeggi, Karen Kramer, Raymond Hames, Evan J. Kiely, Cristina Gomes, Hillard Kaplan, Michael Gurven

ESI Publications

Objectives—Grooming has important utilitarian and social functions in primates but little is known about grooming and its functional analogues in traditional human societies. We compare human grooming to typical primate patterns to test its hygienic and social functions.

Materials and Methods—Bayesian phylogenetic analyses were used to derive expected human grooming time given the potential associations between grooming, group size, body size, terrestriality, and several climatic variables across 69 primate species. This was compared against observed times dedicated to grooming, other hygienic behavior and conversation among the Maya, Pumé, Sanöma, Tsimane’, Yanomamö, and Ye’kwana (mean number of behavioral scans …

Deliberation Favours Social Efficiency By Making People Disregard Their Relative Shares: Evidence From Usa And India, Valerie Capraro, Brice Corgnet, Antonio M. Espín, Roberto Hernán-González

ESI Publications

Groups make decisions on both the production and the distribution of resources. These decisions typically involve a tension between increasing the total level of group resources (i.e. social efficiency) and distributing these resources among group members (i.e. individuals’ relative shares). This is the case because the redistribution process may destroy part of the resources, thus resulting in socially inefficient allocations. Here we apply a dual-process approach to understand the cognitive underpinnings of this fundamental tension. We conducted a set of experiments to examine the extent to which different allocation decisions respond to intuition or deliberation. In a newly developed approach, …

Cognitive Performance Across The Life Course Of Bolivian Forager-Farmers With Limited Schooling, Michael Gurven, Eric Fuerstenberg, Benjamin C. Trumble, Jonathan Stieglitz, Bret Beheim, Helen Davis, Hillard Kaplan

ESI Publications

Cognitive performance is characterized by at least two distinct life course trajectories. Many cognitive abilities (e.g. “effortful processing” abilities including fluid reasoning, and processing speed) improve throughout early adolescence and start declining in early adulthood, while other abilities (e.g. “crystallized” abilities like vocabulary breadth) improve throughout adult life, remaining robust even at late ages. Although schooling may impact performance and cognitive “reserve”, it has been argued that these age patterns of cognitive performance are human universals. Here we examine age patterns of cognitive performance among Tsimane forager-horticulturalists of Bolivia, and test whether schooling is related to differences in cognitive performance …

Growth References For Tsimane Forager-Horticulturalists Of The Bolivian Amazon, Aaron D. Blackwell, Samuel S. Urlacher, Bret Beheim, Christopher Von Rueden, Adrian V. Jaeggi, Jonathan Stieglitz, Benjamin C. Trumble, Michael Gurven, Hillard Kaplan

ESI Publications

Objectives—Growth standards and references currently used to assess population and individual health are derived primarily from urban populations, including few individuals from indigenous or subsistence groups. Given environmental and genetic differences, growth may vary in these populations. Thus, there is a need to assess whether international standards are appropriate for all populations, and to produce population specific references if growth differs. Here we present and assess growth references for the Tsimane, an indigenous population of Bolivian forager-horticulturalists.

Methods—Mixed cross-sectional/longitudinal anthropometrics (9,614 individuals; 30,118 observations; ages 0–29 years) were used to generate centile curves and Lambda-Mu-Sigma (LMS) tables for …

Salivary Microbiomes Of Indigenous Tsimane Mothers And Infants Are Distinct Despite Frequent Premastication, Cliff S. Han, Melanie Ann Martin, Armand E.K. Dichosa, Ashlynn R. Daughton, Seth Frietze, Hillard Kaplan, Michael D. Gurven, Joe Alcock

ESI Publications

Background. Premastication, the transfer of pre-chewed food, is a common infant and young child feeding practice among the Tsimane, forager-horticulturalists living in the Bolivian Amazon. Research conducted primarily with Western populations has shown that infants harbor distinct oral microbiota from their mothers. Premastication, which is less common in these populations, may influence the colonization and maturation of infant oral microbiota, including via transmission of oral pathogens. We collected premasticated food and saliva samples from Tsimane mothers and infants (9-24 months of age) to test for evidence of bacterial transmission in premasticated foods and overlap in maternal and infant salivary …

Angels And Demons: Using Behavioral Types In A Real-Effort Moral Dilemma To Identify Expert Traits, Hernan Bejarano, Ellen P. Green, Stephen Rassenti

ESI Publications

In this article, we explore how independently reported measures of subjects' cognitive capabilities, preferences, and sociodemographic characteristics relate to their behavior in a real-effort moral dilemma experiment. To do this, we use a unique dataset, the Chapman Preferences and Characteristics Instrument Set (CPCIS), which contains over 30 standardized measures of preferences and characteristics. We find that simple correlation analysis provides an incomplete picture of how individual measures relate to behavior. In contrast, clustering subjects into groups based on observed behavior in the real-effort task reveals important systematic differences in individual characteristics across groups. However, while we find more differences, these …

Conflict Or Congruence? Maternal And Infant-Centric Factors Associated With Shorter Exclusive Breastfeeding Durations Among The Tsimane, Melanie A. Martin, Geni Garcia, Hillard Kaplan, Michael Gurven

ESI Publications

No abstract provided.

Cardiovascular Disease And Type 2 Diabetes In Evolutionary Perspective: A Critical Role For Helminths?, Michael D. Gurven, Benjamin C. Trumble, Jonathan Stieglitz, Aaron D. Blackwell, David E. Michalik, Caleb E. Finch, Hillard Kaplan

ESI Publications

Heart disease and type 2 diabetes are commonly believed to be rare among contemporary subsistencelevel human populations, and by extension prehistoric populations. Although some caveats remain, evidence shows these diseases to be unusual among well-studied hunter-gatherers and other subsistence populations with minimal access to healthcare. Here we expand on a relatively new proposal for why these and other populations may not show major signs of these diseases. Chronic infections, especially helminths, may offer protection against heart disease and diabetes through direct and indirect pathways. As part of a strategy to insure their own survival and reproduction, helminths exert multiple cardio-protective …

An Experimental Investigation Of Simultaneous Multi-Battle Contests With Complementarities, Cary Deck, Sudipta Sarangi, Matt Wiser

ESI Publications

This paper reports the results of laboratory experiments that are designed to test theoretical predictions in a multi-battle contest with value complementarities among the battles. The specific setting is a game of Hex where control of each region is determined by a Tullock contest and the overall winner is determined by the combination of claimed regions. We find that in a game with only a few regions, aggregate behavior across regions is largely consistent with the theoretical predictions. However, examining individual level behavior suggests that bidders are not behaving in accordance with the model, but often pursue specific winning combinations. …

An Epigenetic Clock Analysis Of Race/Ethnicity, Sex, And Coronary Heart Disease, Steve Horvath, Michael Gurven, Morgan E. Levine, Benjamin C. Trumble, Hillard Kaplan, Hooman Allayee, Beate R. Ritz, Brian Chen, Ake T. Lu, Tammy M. Rickabaugh, Beth D. Jamieson, Dianjianyi Sun, Shengxu Li, Wei Chen, Lluis Quintana-Murci, Maud Fagny, Michael S. Kobor, Philip S. Tsao, Alexander P. Reiner, Kerstin L. Edlefsen, Devin Absher, Themistocles L. Assimes

ESI Publications

Background: Epigenetic biomarkers of aging (the “epigenetic clock”) have the potential to address puzzling findings surrounding mortality rates and incidence of cardio-metabolic disease such as: (1) women consistently exhibiting lower mortality than men despite having higher levels of morbidity; (2) racial/ethnic groups having different mortality rates even after adjusting for socioeconomic differences; (3) the black/white mortality cross-over effect in late adulthood; and (4) Hispanics in the United States having a longer life expectancy than Caucasians despite having a higher burden of traditional cardio-metabolic risk factors.

Results: We analyzed blood, saliva, and brain samples from seven different racial/ethnic groups. …

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 …

Indirect Reciprocity, Resource Sharing, And Environmental Risk: Evidence From Field Experiments In Siberia, E. Lance Howe, James J. Murphy, Drew Gerkey, Colin Thor West

ESI Publications

Integrating information from existing research, qualitative ethnographic interviews, and participant observation, we designed a field experiment that introduces idiosyncratic environmental risk and a voluntary sharing decision into a standard public goods game. Conducted with subsistence resource users in rural villages on the Kamchatka Peninsula in Northeast Siberia, we find evidence consistent with a model of indirect reciprocity and local social norms of helping the needy. When participants are allowed to develop reputations in the experiments, as is the case in most small-scale societies, we find that sharing is increasingly directed toward individuals experiencing hardship, good reputations increase aid, and the …

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 …

An Experimental Investigation Of Procurement Auctions With Asymmetric Sellers, John Aloysius, Cary A. Deck, Li Hao, Ryan French

ESI Publications

Electronic reverse auctions are a commonly used procurement mechanism. Research to date has focused on suppliers who are ex ante symmetric in that their costs are drawn from a common distribution. However, in many cases a seller's range of potential costs depends on their own operations, location, or economies of scale and scope. Thus, understanding how different bidder types impact auction outcomes is key when designing an auction. This paper reports the results of the first controlled laboratory experiment designed to compare prices between first-price and second-price procurement auctions for homogeneous goods when seller cost types are asymmetric and the …

State Dependent Price Setting Rules Under Implicit Thresholds: An Experiment, Justin Deloy Leblanc, Andrea Civelli, Cary A. Deck, Klajdi Bregu

ESI Publications

How firms make their pricing decisions is a fundamental question of macroeconomics. We use a laboratory experiment to examine individual choices in a price updating task that provide insight into how well state dependent models reflect behavior. We find that in general subjects behave as if they recognize the importance of a state dependent pricing strategy, but they are unable to ascertain this threshold with precision and they also exhibit a substantial degree of time dependence. As a result, they update prices too frequently, and perform statistically significantly fewer real effort profit-generating tasks than theoretically optimal under full state dependence, …

The Financial Power Of The Powerless: Socio-Economic Status And Interest Rates Under Weak Rule Of Law, Timur Kuran, Jared Rubin

ESI Publications

In advanced economies interest rates vary inversely with the borrower's socio-economic status, which itself depends inversely on default risk. These relationships depend on the impartiality of the law. Where the law is markedly biased in favour of certain groups, the latter will pay a surcharge for capital. Legal power, as measured by privileges before the law, thus undermines financial power, the capacity to borrow cheaply. Developing this argument, this paper also tests it through judicial records from Ottoman Istanbul, 1602-1799. Three privileged Ottoman groups—men, Muslims, and titled elites—all paid relatively high interest rates conditional on various loan characteristics.

Religious Identity And The Provision Of Public Goods: Evidence From The Indian Princely States, Latika Chaudhary, Jared Rubin

ESI Publications

This paper describes a simple model of how a ruler’s religious identity affects public goods provision. Our primary insight is that rulers reduce public goods expenditures to a greater degree when there are privately-provided substitutes excludable by religion.The basic idea is that if the good is provided privately to the ruler’s co-religionists, the ruler faces weaker incentives to provide this public good because his co-religionists receive lower marginal utility from its provision. Testing such a conjecture is an empirical challenge, however, since the religious identity of rulers rarely varies over time and place. We address this problem by exploiting …

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 …

Humankind In Civilization’S Extended Order: A Tragedy, The First Part, Bart J. Wilson

ESI Publications

This article is a short, scientific story of the labyrinthian human career, of humankind’s place in the natural order of the world, and of the evolution of moral rules and rule following that make the extended order of civilization possible. Drawing upon work in anthropology, biology, and linguistics, I weave a science-based narrative of how Homo sapiens came to be the only primate to convert enemy aliens into trading friends. It is a Goethean story of the human condition that postulates the common origins of and modern tension between Pleistocene and Anthropocene morality. It is also a Hayekian story of …

Further Towards A Theory Of The Emergence Of Property, Bart J. Wilson

ESI Publications

This article explores the emergence of property as a moral convention. To understand this process I make use of several laboratory experiments on property in its nascence. These experiments illustrate how a rule of property arises from our knowledge of what is morally right, and not vice versa. I also argue that while the ultimate end of property is our interest in using things, the proximate end of property is not losing them, i.e., the end of a rule of property is to secure from morally unfounded harm.

Conflicted Emotions Following Trust-Based Interaction, Eric Schniter, Roman M. Sheremeta, Timothy W. Shields

ESI Publications

We observed reports of conflicted (concurrent positive and negative) emotions activated after interactions in the Trust game. Our analyses reveal that activation of 20 emotional states following trust-based interaction is better explained by predictions derived from a multi-dimensional Recalibrational perspective than by predictions derived from two-dimensional Valence and Arousal perspectives. The Recalibrational perspective proposes that emotions are activated according to their functional features – for example, emotions help people achieve short or long-sighted goals by up or down-regulating behavioral propensities, whereas Valence and Arousal perspectives consider simpler hedonic dimensions lacking functional specificity. The Recalibrational perspective is also distinguished from the …

To Trust, Or Not To Trust: Cognitive Reflection In Trust Games, Brice Corgnet, Antonio M. Espín, Roberto Hernán-González, Praveen Kujal, Stephen Rassenti

ESI Publications

We present results from two studies that show a positive relation between cognitive reflection and trusting behavior, but no significant relation with trustworthy behavior. Our finding holds regardless of individual distributional social preferences and risk aversion. Our results add to a growing body of literature that illustrates the role of cognitive ability in helping explain outcomes in economic experiments.