Cross-cousin marriage among Tsimane forager-horticulturalists during demographic transition and market integration.

Although still prevalent in many human societies, the practice of cousin marriage has precipitously declined in populations undergoing rapid demographic and socioeconomic change. However, it is still unclear whether changes in the structure of the marriage pool or changes in the fitness-relevant consequences of cousin marriage more strongly influence the frequency of cousin marriage. Here, we use genealogical data collected by the Tsimane Health and Life History Project to show that there is a small but measurable decline in the frequency of first cross-cousin marriage since the mid-twentieth century.

Women's subsistence strategies predict fertility across cultures, but context matters.

While it is commonly assumed that farmers have higher, and foragers lower, fertility compared to populations practicing other forms of subsistence, robust supportive evidence is lacking. We tested whether subsistence activities-incorporating market integration-are associated with fertility in 10,250 women from 27 small-scale societies and found considerable variation in fertility. This variation did not align with group-level subsistence typologies.

Poor Oral Health Is Associated With Inflammation, Aortic Valve Calcification, and Brain Volume Among Forager-Farmers.

Poor oral health is associated with cardiovascular disease and dementia. Potential pathways include sepsis from oral bacteria, systemic inflammation, and nutritional deficiencies. However, in post-industrialized populations, links between oral health and chronic disease may be confounded because the lower socioeconomic exposome (poor diet, pollution, and low physical activity) often entails insufficient dental care.

Testosterone is positively associated with coronary artery calcium in a low cardiovascular disease risk population.

Background: In industrialized populations, low male testosterone is associated with higher rates of cardiovascular mortality. However, coronary risk factors like obesity impact both testosterone and cardiovascular outcomes. Here, we assess the role of endogenous testosterone on coronary artery calcium in an active subsistence population with relatively low testosterone levels, low cardiovascular risk and low coronary artery calcium scores.

Adolescence is characterized by more sedentary behaviour and less physical activity even among highly active forager-farmers.

Over 80% of adolescents worldwide are insufficiently active, posing massive public health and economic challenges. Declining physical activity (PA) and sex differences in PA consistently accompany transitions from childhood to adulthood in post-industrialized populations and are attributed to psychosocial and environmental factors. An overarching evolutionary theoretical framework and data from pre-industrialized populations are lacking.

Metapopulation dynamics of SARS-CoV-2 transmission in a small-scale Amazonian society.

The severity of infectious disease outbreaks is governed by patterns of human contact, which vary by geography, social organization, mobility, access to technology and healthcare, economic development, and culture. Whereas globalized societies and urban centers exhibit characteristics that can heighten vulnerability to pandemics, small-scale subsistence societies occupying remote, rural areas may be buffered. Accordingly, voluntary collective isolation has been proposed as one strategy to mitigate the impacts of COVID-19 and other pandemics on small-scale Indigenous populations with minimal access to healthcare infrastructure.

ε is associated with higher fecundity in a natural fertility population.

In many populations, the aε (ε) allele increases the risk for several chronic diseases of aging, including dementia and cardiovascular disease; despite these harmful effects at later ages, the ε allele remains prevalent. We assess the impact of ε on fertility and its proximate determinants (age at first reproduction, interbirth interval) among the Tsimane, a natural fertility population of forager-horticulturalists. Among 795 women aged 13 to 90 (20% ε carriers), those with at least one ε allele had 0.

Inheritance and inequality among nomads of South Siberia.

At the headwaters of the Yenisei River in Tuva and northern Mongolia, nomadic pastoralists move between camps in a seasonal rotation that facilitates their animals' access to high-quality grasses and shelter. The use and informal ownership of these camps depending on season helps illustrate evolutionary and ecological principles underlying variation in property relations. Given relatively stable patterns of precipitation and returns to capital improvement, families generally benefit from reusing the same camps year after year.

Adolescence is characterized by more sedentary behavior and less physical activity even among highly active forager-farmers.

Over 80% of adolescents worldwide are insufficiently active, posing massive public health and economic challenges. Declining physical activity (PA) and sex differences in PA consistently accompany transitions from childhood to adulthood in post-industrialized populations and are attributed to psychosocial and environmental factors. An overarching evolutionary theoretical framework and data from pre-industrialized populations are lacking.

Natural selection of immune and metabolic genes associated with health in two lowland Bolivian populations.

A growing body of work has addressed human adaptations to diverse environments using genomic data, but few studies have connected putatively selected alleles to phenotypes, much less among underrepresented populations such as Amerindians. Studies of natural selection and genotype-phenotype relationships in underrepresented populations hold potential to uncover previously undescribed loci underlying evolutionarily and biomedically relevant traits. Here, we worked with the Tsimane and the Moseten, two Amerindian populations inhabiting the Bolivian lowlands.

Female cooperative labour networks in hunter-gatherers and horticulturalists.

Cooperation in food acquisition is a hallmark of the human species. Given that costs and benefits of cooperation vary among production regimes and work activities, the transition from hunting-and-gathering to agriculture is likely to have reshaped the structure of cooperative subsistence networks. Hunter-gatherers often forage in groups and are generally more interdependent and experience higher short-term food acquisition risk than horticulturalists, suggesting that cooperative labour should be more widespread and frequent for hunter-gatherers.

Repercussions of patrilocal residence on mothers' social support networks among Tsimane forager-farmers.

While it is commonly thought that patrilocality is associated with worse outcomes for women and their children due to lower social support, few studies have examined whether the structure of female social networks covaries with post-marital residence. Here, we analyse scan sample data collected among Tsimane forager-farmers. We compare the social groups and activity partners of 181 women residing in the same community as their parents, their husband's parents, both or neither.

Prevalence of dementia and mild cognitive impairment in indigenous Bolivian forager-horticulturalists.

Introduction: We evaluated the prevalence of dementia and mild cognitive impairment (MCI) in indigenous Tsimane and Moseten, who lead a subsistence lifestyle.

Methods: Participants from population-based samples ≥ 60 years of age (n = 623) were assessed using adapted versions of the Modified Mini-Mental State Examination, informant interview, longitudinal cognitive testing and brain computed tomography (CT) scans.

Results: Tsimane exhibited five cases of dementia (among n = 435; crude prevalence = 1.

The Indigenous South American Tsimane Exhibit Relatively Modest Decrease in Brain Volume With Age Despite High Systemic Inflammation.

Brain atrophy is correlated with risk of cognitive impairment, functional decline, and dementia. Despite a high infectious disease burden, Tsimane forager-horticulturists of Bolivia have the lowest prevalence of coronary atherosclerosis of any studied population and present few cardiovascular disease (CVD) risk factors despite a high burden of infections and therefore inflammation. This study (a) examines the statistical association between brain volume (BV) and age for Tsimane and (b) compares this association to that of 3 industrialized populations in the United States and Europe.

Do wealth and inequality associate with health in a small-scale subsistence society?

In high-income countries, one's relative socio-economic position and economic inequality may affect health and well-being, arguably via psychosocial stress. We tested this in a small-scale subsistence society, the Tsimane, by associating relative household wealth (n = 871) and community-level wealth inequality (n = 40, Gini = 0.15-0.

Invasive Treatments for Low Back Disorders.

Objective: This abbreviated version of the American College of Occupational and Environmental Medicine's Low Back Disorders guideline reviews the evidence and recommendations developed for invasive treatments used to manage low back disorders.

Methods: Comprehensive systematic literature reviews were accomplished with article abstraction, critiquing, grading, evidence table compilation, and guideline finalization by a multidisciplinary expert panel and extensive peer-review to develop evidence-based guidance. Consensus recommendations were formulated when evidence was lacking and often relied on analogy to other disorders for which evidence exists.

Gains to cooperation drive the evolution of egalitarianism.

What conditions favour egalitarianism, that is, muted hierarchies with relatively equal distributions of resources? Here, we combine the hawk-dove and prisoner's dilemma games to model the effects of economic defensibility, costs of competition and gains from cooperation on egalitarianism, operationalized as the absence of hawks. We show that a 'leveller' strategy, which punishes hawkishness in the hawk-dove game with defection in the prisoner's dilemma, can be evolutionarily stable provided that the gains from cooperation are high relative to the benefits of hawkishness. Under these conditions, rare mutant levellers select for hawks that acquiesce to punishment by playing dove.

The effects of hot forging on the preform additive manufactured 316 stainless steel parts.

Additive Manufacture (AM) offers great potential for creating metallic parts for high end products used in critical application i.e. aerospace and biomedical engineering.

Productivity loss associated with functional disability in a contemporary small-scale subsistence population.

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.

Matriliny reverses gender disparities in inflammation and hypertension among the Mosuo of China.

Women experience higher morbidity than men, despite living longer. This is often attributed to biological differences between the sexes; however, the majority of societies in which these disparities are observed exhibit gender norms that favor men. We tested the hypothesis that female-biased gender norms ameliorate gender disparities in health by comparing gender differences in inflammation and hypertension among the matrilineal and patrilineal Mosuo of China.

Rapidly declining body temperature in a tropical human population.

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.