Digital Commons Network^™

Quantitative Description Of The Pastoral Economy Of Western Tuvan Nomads, Paul L. Hooper

ESI Publications

Nomadic pastoralism persists at a substantial scale in Tuva and neighboring regions of Inner Asia. Tuvan pastoral lifeways reflect adaptations to both local environments and current economic realities. Much of our quantitative understanding of the economics of Tuvan nomads is derived from data collected in the first half of the 20th century. Accordingly, this paper provides an updated picture of the inner workings of nomadic households using data collected in Barun-Khemchik and Bai-Taiga provinces in 2013–2015. It analyzes herd composition and size, and compares the frequency of different animals kept today with values recorded in Tuva in 1916 and 1931. …

Productivity Loss Associated With Functional Disability In A Contemporary Small-Scale Subsistence Population, Jonathan Stieglitz, Paul L. Hooper, Benjamin C. Trumble, Hillard Kaplan, Michael D. Gurven

ESI Publications

In comparative cross-species perspective, humans experience unique physical impairments with potentially large consequences. Quantifying the burden of impairment in subsistence populations is critical for understanding selection pressures underlying strategies that minimize risk of production deficits. We examine among forager-horticulturalists whether compromised bone strength (indicated by fracture and lower bone mineral density, BMD) is associated with subsistence task cessation. We also estimate the magnitude of productivity losses associated with compromised bone strength. Fracture is associated with cessation of hunting, tree chopping, and walking long distances, but not tool manufacture. Age-specific productivity losses from hunting cessation associated with fracture and lower BMD …

Deliberation Enhances The Confirmation Bias In Politics, David L. Dickinson

ESI Publications

The confirmation bias, unlike other decision biases, has been shown both empirically and in theory to be enhanced with deliberation. This suggests that limited attention, reduced deliberation, or limited available cognitive resources may moderate this bias. We aimed to test this hypothesis using a validated confirmation bias task in conjunction with a protocol that randomly assigned individuals to one week of at-home sleep restriction (SR) or well-rested (WR) sleep levels. We also used a measure of cognitive reflection as an additional proxy for deliberation in our analysis. We tested the hypotheses that the confirmation bias would be stronger for WR …

The Effect Of Sleep On Public Good Contributions And Punishment: Experimental Evidence, Jeremy Clark, David L. Dickinson

ESI Publications

We investigate the effect of a full week of sleep restriction (SR) vs. well-restedness (WR) on contributions in a common public good experiment, the voluntary contributions mechanism (VCM). We examine the effect of sleep manipulation on decisions regarding both contributions and punishment of non-contributors. Actigraphy devices are used to confirm that our random assignment to sleep condition generates significant differences in objective nightly sleep duration and sleepiness. We find that when punishment is unavailable public good contributions do not differ by SR/WR assignment. When punishment is available, we find evidence that SR subjects contribute more than WR subjects, respond more …

Rapidly Declining Body Temperature In A Tropical Human Population, Michael Gurven, Thomas Kraft, Sarah Alami, Juan Copajira Adrian, Edhitt Cortez Linares, Daniel Cummings, Daniel Eid Rodriguez, Paul L. Hooper, Adrian Jaeggi, Raul Quispe Gutierrez, Ivan Maldonado Suarez, Edmond Seabright, Hillard Kaplan, Jonathan Stieglitz, Benjamin C. Trumble

ESI Publications

Normal human body temperature (BT) has long been considered to be 37.0°C. Yet, BTs have declined over the past two centuries in the United States, coinciding with reductions in infection and increasing life expectancy. The generality of and reasons behind this phenomenon have not yet been well studied. Here, we show that Bolivian forager-farmers (n = 17,958 observations of 5481 adults age 15+ years) inhabiting a pathogen-rich environment exhibited higher BT when first examined in the early 21st century (~37.0°C). BT subsequently declined by ~0.05°C/year over 16 years of socioeconomic and epidemiological change to ~36.5°C by 2018. As predicted, …

The Role Of Dispersal And School Attendance On Reproductive Dynamics In Small, Dispersed Populations: Choyeros Of Baja California Sur, Mexico, Shane Macfarlan, Ryan Schacht, Eric Schniter, Juan José Garcia, Diego Guevara Beltran, Jory Lerback

ESI Publications

Individuals from small populations face challenges to initiating reproduction because stochastic demographic processes create local mate scarcity. In response, flexible dispersal patterns that facilitate the movement of individuals across groups have been argued to reduce mate search costs and inbreeding depression. Furthermore, factors that aggregate dispersed peoples, such as rural schools, could lower mate search costs through expansion of mating markets. However, research suggests that dispersal and school attendance are costly to fertility, causing individuals to delay marriage and reproduction. Here, we investigate the role of dispersal and school attendance on marriage and reproductive outcomes using a sample of 54 …

Evidence For Height And Immune Function Trade-Offs Among Preadolescents In A High Pathogen Population, Angela R. Garcia, Aaron Blackwell, Benjamin C. Trumble, Jonathan Stieglitz, Hillard Kaplan, Michael Gurven

ESI Publications

Background

In an energy-limited environment, caloric investments in one characteristic should trade-off with investments in other characteristics. In high pathogen ecologies, biasing energy allocation towards immune function over growth would be predicted, given strong selective pressures against early-life mortality.

Methodology

In the present study, we use flow cytometry to examine trade-offs between adaptive immune function (T cell subsets, B cells), innate immune function (natural killer cells), adaptive to innate ratio and height-for-age z scores (HAZ) among young children (N = 344; aged 2 months–8 years) in the Bolivian Amazon, using maternal BMI and child weight-for-height z scores (WHZ) as …

Multiplex Network Ties And The Spatial Diffusion Of Radical Innovations: Martin Luther’S Leadership In The Early Reformation, Sascha O. Becker, Yuan Hsiao, Steven Pfaff, Jared Rubin

ESI Publications

This article analyzes Martin Luther’s role in spreading the early Reformation, one of the most important episodes of radical institutional change in the last millennium. We argue that social relations played a key role in its diffusion because the spread of heterodox ideologies and their eventual institutionalization relied not only on private “infection” through exposure to innovation but also on active conversion and promotion of that new faith through personal ties. We conceive of that process as leader-to-follower directional influence originating with Luther and flowing to local elites through personal ties. Based on novel data on Luther’s correspondence, Luther’s visits, …

A Simple, Ecologically Rational Rule For Settling Found Property Disputes, Bart J. Wilson

ESI Publications

Who has property in a found item X, which is contained in Y? The finder of X or the person who has property in Y? The common law says it depends. It depends upon whether the owner of Y knew about X, or whether X was lost or mislaid, or how small the weight of X is relative to Y (as compared to its value), or whether the finder was an employee of the owner of Y, to name just a few. Wilson (2020) hypothesizes that humans universally cognize property as being contained in a …

Consistent Differences In A Virtual World Model Of Ape Societies, Bart J. Wilson, Sarah F. Brosnan, Elizabeth V. Lonsdorf, Crickette M. Sanz

ESI Publications

Practical and ethical constraints limit our ability to experimentally test socioecological theory in wild primates. We took an alternate approach to model this, allowing groups of humans to interact in a virtual world in which they had to find food and interact with both ingroup and outgroup avatars to earn rewards. We altered ratios and distributions of high- and low-value foods to test the hypothesis that hominoids vary with regards to social cohesion and intergroup tolerance due to their feeding ecology. We found larger nesting clusters and decreased attacks on outgroup competitors in the Bonobo condition versus the Chimpanzee condition, …

Immune Function During Pregnancy Varies Between Ecologically Distinct Populations, Carmen Hové, Benjamin C. Trumble, Amy S. Anderson, Jonathan Stieglitz, Hillard Kaplan, Michael Gurven, Aaron Blackwell

ESI Publications

Background and objectives

Among placental mammals, females undergo immunological shifts during pregnancy to accommodate the fetus (i.e. fetal tolerance). Fetal tolerance has primarily been characterized within post-industrial populations experiencing evolutionarily novel conditions (e.g. reduced pathogen exposure), which may shape maternal response to fetal antigens. This study investigates how ecological conditions affect maternal immune status during pregnancy by comparing the direction and magnitude of immunological changes associated with each trimester among the Tsimane (a subsistence population subjected to high pathogen load) and women in the USA.

Methodology

Data from the Tsimane Health and Life History Project (N = 935) and …

Paternal Provisioning Results From Ecological Change, Ingela Alger, Paul L. Hooper, Donald Cox, Jonathan Stieglitz, Hillard S. Kaplan

ESI Publications

Paternal provisioning is ubiquitous in human subsistence societies and unique among apes. How could paternal provisioning have emerged from promiscuous or polygynous mating systems that characterize other apes? An anomalous provisioning male would encounter a social dilemma: Since this investment in prospective offspring can be expropriated by other males, this investment is unlikely to increase the provisioner’s fitness. We present an ecological theory of the evolution of human paternal investment. Ecological change favoring reliance on energetically rich, difficult-to-acquire resources increases payoffs to paternal provisioning due to female–male and/or male–male complementarities. Paternal provisioning becomes a viable reproductive strategy when complementarities are …

Asset Price Volatility And Price Extrema, Carey Caginalp, Gunduz Caginalp

ESI Publications

The relationship between price volatility and expected price market extremum is examined using a fundamental economics model of supply and demand. By examining randomness through a microeconomic setting, we obtain the implications of randomness in the supply and demand, rather than assuming that price has randomness on an empirical basis. Within a general setting of changing fundamentals, the volatility is maximum when expected prices are changing most rapidly, with the maximum of volatility reached prior to the maximum of expected price. A key issue is that randomness arises from the supply and demand, and the variance in the stochastic differential …

News-Driven Expectations And Volatility Clustering, Sabiou M. Inoua

ESI Publications

Financial volatility obeys two fascinating empirical regularities that apply to various assets, on various markets, and on various time scales: it is fat-tailed (more precisely power-law distributed) and it tends to be clustered in time. Many interesting models have been proposed to account for these regularities, notably agent-based models, which mimic the two empirical laws through a complex mix of nonlinear mechanisms such as traders switching between trading strategies in highly nonlinear way. This paper explains the two regularities simply in terms of traders’ attitudes towards news, an explanation that follows from the very traditional dichotomy of financial market participants, …