Evolutionary public health: introducing the concept

Mothers of twins had higher old-age survival than mothers of singletons in Estonian 19th-century birth cohorts

STUDY QUESTION

Do the mothers of twins and singletons differ regarding post-partum and old-age mortality?

SUMMARY ANSWER

Twin deliveries were associated with higher post-partum maternal mortality than singleton deliveries, but the lifetime post-partum mortality risk was similar for mothers of twins and singletons; survival of twinners was higher than survival of the mothers of singletons after the 67th lifespan percentile.

WHAT IS KNOWN ALREADY

Twinning is typically associated with higher post-partum maternal mortality. The evidence about whether twinning incurs long-term survival costs of reproduction or is a trait pertinent to long-lived women is scarce and contradictory.

STUDY DESIGN, SIZE, DURATION

The study is based on the data of the Estonian Family Register (operating from 1926 to 1943) and involves 5565 mothers of twins and 119 613 mothers of singletons born between 1850 and 1899. The subset for comparing maternal lifespans included 1703-1884 mothers of twins and 19 747-36 690 mothers of singletons.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Post-partum maternal mortality was analyzed in the whole sample (including mothers of a single child) by logistic regression. Most of the analyses were performed in samples where each mother of twins was matched against mothers of singletons based on parity (or number of deliveries), urban versus rural and inland versus coastal origin, whether their lifespan was known, date of birth and age at first birth. Lifespans were compared in linear mixed models. Quantile regression was used to analyze age-dependent variations in maternal mortality rates. All models were adjusted for relevant biodemographic covariates.

MAIN RESULTS AND THE ROLE OF CHANCE

The twinning rate in the whole sample was 4.4%. During the year after giving birth, maternal mortality for twin deliveries was 0.75% (17/2273) and 0.37% (449/122 750) for singleton deliveries (OR = 2.05, 95% CI = 1.21-3.23). However, the lifetime post-partum mortality risk for mothers of twins (0.51%; 28/5557) and singletons (0.37%; 438/119 466) did not differ significantly (OR = 1.38, 95% CI = 0.91-1.98). The life spans of the mothers of twins and singletons did not differ in matched samples. Past the 67th lifespan percentile, the odds of survival were significantly higher for mothers of twins than mothers of singletons, as indicated by non-overlapping 95% confidence intervals.

LIMITATIONS, REASONS FOR CAUTION

Relatively low number of individuals (22 802-28 335) with known age at death in matched datasets due to discontinuation of the register after 1943.

WIDER IMPLICATIONS OF THE FINDINGS

The finding that mothers of twins had higher odds of old-age survival than mothers of singletons is consistent with the contention that twinners represent a non-random subset of women whose robust phenotypic quality allows them to outlive the mothers of singletons in old age.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Estonian Research Council grants PRG1137, PRG2248, and PSG669. The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Aging, Equality and the Human Healthspan

John Davis (New Methuselahs: The Ethics of Life Extension, The MIT Press, Cambridge, 2018) advances a novel ethical analysis of longevity science that employs a three-fold methodology of examining the impact of life extension technologies on three distinct groups: the "Haves", the "Have-nots" and the "Will-nots". In this essay, I critically examine the egalitarian analysis Davis deploys with respect to its ability to help us theorize about the moral significance of an applied gerontological intervention. Rather than focusing on futuristic scenarios of radical life extension, I offer a rival egalitarian analysis that takes seriously (1) the health vulnerabilities of today's aging populations, (2) the health inequalities of the "aging status quo" and, (3) the prospects for the fair diffusion of an aging intervention over the not-so-distant future. Despite my reservations about Davis's focus on "life-extension" vs. increasing the human "healthspan", I agree with his central conclusion that an aging intervention would be, on balance, a good thing and that we should fund such research aggressively. But, I make an even stronger case and conjecture that an intervention that slows down the rate of molecular and cellular decline from the inborn aging process will likely be one of the most important public health advancements of the twenty-first century. This is so because aging is the most prevalent risk factor for chronic disease, frailty and disability, and it is estimated that there will be over 2 billion persons age > 60 by the year 2050.

An evolutionary timeline of the oxytocin signaling pathway

Oxytocin is a neuropeptide associated with both psychological and somatic processes like parturition and social bonding. Although oxytocin homologs have been identified in many species, the evolutionary timeline of the entire oxytocin signaling gene pathway has yet to be described. Using protein sequence similarity searches, microsynteny, and phylostratigraphy, we assigned the genes supporting the oxytocin pathway to different phylostrata based on when we found they likely arose in evolution. We show that the majority (64%) of genes in the pathway are 'modern'. Most of the modern genes evolved around the emergence of vertebrates or jawed vertebrates (540 - 530 million years ago, 'mya'), including OXTR, OXT and CD38. Of those, 45% were under positive selection at some point during vertebrate evolution. We also found that 18% of the genes in the oxytocin pathway are 'ancient', meaning their emergence dates back to cellular organisms and opisthokonta (3500-1100 mya). The remaining genes (18%) that evolved after ancient and before modern genes were classified as 'medium-aged'. Functional analyses revealed that, in humans, medium-aged oxytocin pathway genes are highly expressed in contractile organs, while modern genes in the oxytocin pathway are primarily expressed in the brain and muscle tissue.

Maternal capital predicts investment in infant growth and development through lactation

Introduction

Maternal capital (MC) is a broad term from evolutionary biology, referring to any aspects of maternal phenotype that represent resources available for investment in offspring. We investigated MC in breastfeeding mothers of late preterm and early term infants, examining its relationship with infant and breastfeeding outcomes. We also determined whether MC modified the effect of the relaxation intervention on these outcomes.

Methods

The data was collected as part of a randomized controlled trial investigating breastfeeding relaxation in 72 mothers of late preterm and early term infants. Indicators of MC (socioeconomic, social, somatic, reproductive, psychological, and cognitive) were collected at baseline at 2-3 weeks post-delivery. Principal Component Analysis was conducted for the MC measures and two components were identified: 1."Subjective" maternal capital which included stress and depression scores, and 2."Objective" maternal capital which included height, infant birth weight, and verbal memory. Univariate linear regression was conducted to assess the relationship between objective and subjective MC (predictors) and infant growth, infant behavior, maternal behavior, and infant feeding variables (outcomes) at 6-8 weeks. The interaction of MC and intervention assignment with outcomes was assessed.

Results

Higher objective MC was significantly associated with higher infant weight (0.43; 95%CI 0.21,0.66) and length z-scores (0.47; 95%CI 0.19,0.76), shorter duration of crying (-17.5; 95%CI -33.2,-1.9), and lower food (-0.28; 95%CI -0.48,-0.08) and satiety responsiveness (-0.17; 95%CI -0.31,-0.02) at 6-8 weeks. It was also associated with greater maternal responsiveness to infant cues (-0.05, 95%CI -0.09,-0.02 for non-responsiveness). Greater subjective maternal capital was significantly associated with higher breastfeeding frequency (2.3; 95%CI 0.8,3.8) and infant appetite (0.30; 95%CI 0.07,0.54). There was a significant interaction between the intervention assignment and objective MC for infant length, with trends for infant weight and crying, which indicated that the intervention had greater effects among mothers with lower capital.

Conclusion

Higher MC was associated with better infant growth and shorter crying duration. This was possibly mediated through more frequent breastfeeding and prompt responsiveness to infant cues, reflecting greater maternal investment. The findings also suggest that a relaxation intervention was most effective among those with low MC, suggesting some reduction in social inequalities in health.

An evolutionary perspective on social inequality and health disparities: Insights from the producer-scrounger game

There is growing concern with social disparities in health, whether relating to gender, ethnicity, caste, socio-economic position or other axes of inequality. Despite addressing inequality, evolutionary biologists have had surprisingly little to say on why human societies are prone to demonstrating exploitation. This article builds on a recent book, 'The Metabolic Ghetto', describing an overarching evolutionary framework for studying all forms of social inequality involving exploitation. The dynamic 'producer-scrounger' game, developed to model social foraging, assumes that some members of a social group produce food, and that others scrounge from them. An evolutionary stable strategy emerges when neither producers nor scroungers can increase their Darwinian fitness by changing strategy. This approach puts food systems central to all forms of human inequality, and provides a valuable lens through which to consider different forms of gender inequality, socio-economic inequality and racial/caste discrimination. Individuals that routinely adopt producer or scrounger tactics may develop divergent phenotypes. This approach can be linked with life history theory to understand how social dynamics drive health disparities. The framework differs from previous evolutionary perspectives on inequality, by focussing on the exploitation of foraging effort rather than inequality in ecological resources themselves. Health inequalities emerge where scroungers acquire different forms of power over producers, driving increasing exploitation. In racialized societies, symbolic categorization is used to systematically assign some individuals to low-rank producer roles, embedding exploitation in society. Efforts to reduce health inequalities must address the whole of society, altering producer-scrounger dynamics rather than simply targeting resources at exploited groups.

Gender disparities in material and educational resources differ by kinship system

Contemporary inequality exists at an unprecedented scale. Social scientists have emphasized the role played by material wealth in driving its escalation. Evolutionary anthropologists understand the drive to accumulate material wealth as one that is coupled ultimately to increasing reproductive success. Owing to biological caps on reproduction for women, the efficiency of this conversion can differ by gender, with implications for understanding the evolution of gender disparities in resource accumulation. Efficiency also differs according to the type of resources used to support reproductive success. In this paper, we review evolutionary explanations of gender disparities in resources and investigate empirical evidence to support or refute those explanations among matrilineal and patrilineal subpopulations of ethnic Chinese Mosuo, who share an ethnolinguistic identity, but differ strikingly in terms of institutions and norms surrounding kinship and gender. We find that gender differentially predicts income and educational attainment. Men were more likely to report income than women; amounts earned were higher for men overall, but the difference between men and women was minimal under matriliny. Men reported higher levels of educational attainment than women, unexpectedly more so in matrilineal contexts. The results reveal nuances in how biology and cultural institutions affect gender disparities in wealth. This article is part of the theme issue 'Evolutionary ecology of inequality'.

Complexity in Epidemiology and Public Health. Addressing Complex Health Problems Through a Mix of Epidemiologic Methods and Data

Public health and the underlying disease processes are complex, often involving the interaction of biologic, social, psychologic, economic, and other processes that may be nonlinear and adaptive and have other features of complex systems. There is therefore a need to push the boundaries of public health beyond single-factor data analysis and expand the capacity of research methodology to tackle real-world complexities. This article sets out a way to operationalize complex systems thinking in public health, with a particular focus on how epidemiologic methods and data can contribute towards this end. Our proposed framework comprises three core dimensions-patterns, mechanisms, and dynamics-along which complex systems may be conceptualized. These dimensions cover seven key features of complex systems-emergence, interactions, nonlinearity, interference, feedback loops, adaptation, and evolution. We relate this framework to examples of methods and data traditionally used in epidemiology. We conclude that systematic production of knowledge on complex health issues may benefit from: formulation of research questions and programs in terms of the core dimensions we identify, as a comprehensive way to capture crucial features of complex systems; integration of traditional epidemiologic methods with systems methodology such as computational simulation modeling; interdisciplinary work; and continued investment in a wide range of data types. We believe that the proposed framework can support the systematic production of knowledge on complex health problems, with the use of epidemiology and other disciplines. This will help us understand emergent health phenomena, identify vulnerable population groups, and detect leverage points for promoting public health.

Intergenerational transmission of height in a historical population: From taller mothers to larger offspring at birth (and as adults)

Changes in growth and height reflect changes in nutritional status and health. The systematic surveillance of growth can suggest areas for interventions. Moreover, phenotypic variation has a strong intergenerational component. There is a lack of historical family data that can be used to track the transmission of height over subsequent generations. Maternal height is a proxy for conditions experienced by one generation that relates to the health/growth of future generations. Cross-sectional/cohort studies have shown that shorter maternal height is closely associated with lower birth weight of offspring. We analyzed the maternal height and offspring weight at birth in the maternity hospital in Basel, Switzerland, from 1896 to 1939 (N = ∼12,000) using generalized additive models (GAMs). We observed that average height of the mothers increased by ∼4 cm across 60 birth years and that average birth weight of their children shows a similarly shaped and upward trend 28 years later. Our final model (adjusted for year, parity, sex of the child, gestational age, and maternal birth year) revealed a significant and almost linear association between maternal height and birth weight. Maternal height was the second most important variable modeling birth weight, after gestational age. In addition, we found a significant association between maternal height and aggregated average height of males from the same birth years at time of conscription, 19 years later. Our results have implications for public health: When (female/maternal) height increases due to improved nutritional status, size at birth-and subsequently also the height in adulthood of the next generation-increases as well. However, the directions of development in this regard may currently differ depending on the world region.

Effect of basal metabolic rate on lifespan: a sex-specific Mendelian randomization study

Observationally, the association of basal metabolic rate (BMR) with mortality is mixed, although some ageing theories suggest that higher BMR should reduce lifespan. It remains unclear whether a causal association exists. In this one-sample Mendelian randomization study, we aimed to estimate the casual effect of BMR on parental attained age, a proxy for lifespan, using two-sample Mendelian randomization methods. We obtained genetic variants strongly (p-value < 5 × 10^-8) and independently (r² < 0.001) predicting BMR from the UK Biobank and applied them to a genome-wide association study of parental attained age based on the UK Biobank. We meta-analyzed genetic variant-specific Wald ratios using inverse-variance weighting with multiplicative random effects by sex, supplemented by sensitivity analysis. A total of 178 and 180 genetic variants predicting BMR in men and women were available for father's and mother's attained age, respectively. Genetically predicted BMR was inversely associated with father's and mother's attained age (years of life lost per unit increase in effect size of genetically predicted BMR, 0.46 and 1.36; 95% confidence interval 0.07-0.85 and 0.89-1.82), with a stronger association in women than men. In conclusion, higher BMR might reduce lifespan. The underlying pathways linking to major causes of death and relevant interventions warrant further investigation.

The Long-Term Consequences of Early Life Exposure to Tsunami and Conflict on Adolescents in Sri Lanka

The consequences for adolescent health due to early life exposure to natural disasters combined with war are not known. We collected data from adolescents aged 12-13 years in Sri Lanka whose mothers were pregnant during the Indian Ocean tsunami in 2004 in a tsunami-affected region (n = 22), conflict-affected region (n = 35), conflict-plus-tsunami-affected region (n = 29), or controls in areas unaffected by either (n = 24). Adjusted body mass index (BMI)-for-age z-scores were 1.3, 1.0 and 2.0 for conflict, tsunami, and conflict-plus-tsunami, respectively, compared with the control group. Greater skinfold thickness and higher diastolic blood pressure were found in adolescents born in the conflict zone but no differences were found in height, head circumference, and waist circumference, or blood results, with the exception of serum insulin. Being born after a natural disaster or during conflict was associated with increased BMI and body fat during adolescent, which are associated with longer-term risk of noncommunicable disease.

Evolutionary biological perspectives on current social issues of breastfeeding and weaning

Breastfeeding and weaning are actively studied from evolutionary, medical, and social research perspectives because of their close association with infant mortality, lifetime health, and human population dynamics. Each discipline benefits from an interdisciplinary exchange of knowledge regarding the bases, processes, and consequences of these phenomena. However, current social issues related to breastfeeding and weaning have received little attention from an evolutionary biology perspective. We address this gap by reviewing current social issues related to human breastfeeding and weaning in an evolutionary framework. This approach helps build a conceptual framework with the goal of better understanding ultimate causes of or influences on these current social issues. The six social issues reviewed here fall into three categories: the spatiotemporal constraints of breastfeeding, abuse of breast milk as valuable material, and mismatch in breastfeeding practices. Some of these issues have an evolutionary basis. We analyze the structure of these social issues and discuss their possible solutions in terms of extension of the trade-off theory in evolutionary biology. Our discussion on the current social issues in breastfeeding and weaning highlights the effectiveness of an approach rooted in evolutionary theory and biological anthropology.

Associations between Stunting, Wasting and Body Composition: A Longitudinal Study in 6- to 15-Month-Old Kenyan Children

BACKGROUND

Early growth and body composition may influence the risk of obesity and health in adulthood. Few studies have examined how undernutrition is associated with body composition in early life.

OBJECTIVES

We assessed stunting and wasting as correlates of body composition in young Kenyan children.

METHODS

Nested in a randomized controlled nutrition trial, this longitudinal study assessed fat and fat-free mass (FM, FFM) using deuterium dilution technique among children at age 6 and 15 months. This trial was registered at http://controlled-trials.com/ (ISRCTN30012997). Cross-sectional and longitudinal associations between z-score categories of length-for-age (LAZ) or weight-for-length (WLZ) and FM, FFM, fat mass index (FMI), fat-free mass index (FFMI), triceps, and subscapular skinfolds were analyzed by linear mixed models.

RESULTS

Among the 499 children enrolled, breastfeeding declined from 99% to 87%, stunting increased from 13% to 32%, and wasting remained at 2% to 3% between 6 and 15 mo. Compared with LAZ >0, stunted children had a 1.12 kg (95% CI: 0.88, 1.36; P < 0.001) lower FFM at 6 mo and increased to 1.59 kg (95% CI: 1.25, 1.94; P < 0.001) at 15 mo, corresponding to differences of 18% and 17%, respectively. When analyzing FFMI, the deficit in FFM tended to be less than proportional to children's height at 6 mo (P ≤ 0.060) but not at 15 mo (P > 0.40). Stunting was associated with 0.28 kg (95% CI: 0.09, 0.47; P = 0.004) lower FM at 6 mo. However, this association was not significant at 15 mo, and stunting was not associated with FMI at any time point. A lower WLZ was generally associated with lower FM, FFM, FMI, and FFMI at 6 and 15 mo. Differences in FFM, but not FM, increased with time, whereas FFMI differences did not change, and FMI differences generally decreased with time.

CONCLUSIONS

Overall, low LAZ and WLZ among young Kenyan children were associated with reduced lean tissue, which may have long-term health consequences.

Mothers of small-bodied children and fathers of vigorous sons live longer

Life-history traits (traits directly related to survival and reproduction) co-evolve and materialize through physiology and behavior. Accordingly, lifespan can be hypothesized as a potentially informative marker of life-history speed that subsumes the impact of diverse morphometric and behavioral traits. We examined associations between parental longevity and various anthropometric traits in a sample of 4,000-11,000 Estonian children in the middle of the 20th century. The offspring phenotype was used as a proxy measure of parental genotype, so that covariation between offspring traits and parental longevity (defined as belonging to the 90th percentile of lifespan) could be used to characterize the aggregation between longevity and anthropometric traits. We predicted that larger linear dimensions of offspring associate with increased parental longevity and that testosterone-dependent traits associate with reduced paternal longevity. Twelve of 16 offspring traits were associated with mothers' longevity, while three traits (rate of sexual maturation of daughters and grip strength and lung capacity of sons) robustly predicted fathers' longevity. Contrary to predictions, mothers of children with small bodily dimensions lived longer, and paternal longevity was not linearly associated with their children's body size (or testosterone-related traits). Our study thus failed to find evidence that high somatic investment into brain and body growth clusters with a long lifespan across generations, and/or that such associations can be detected on the basis of inter-generational phenotypic correlations.

Glucose-lowering drugs with cardiovascular benefits as modifiers of critical elements of the human life history

The life history theory assumes that all organisms are under selective pressure to harvest external resources and allocate them to maximise fitness: only organisms making the best use of energy obtain the greatest fitness benefits. The trade-off of energy spans four functions: maintenance, growth, reproduction, and defence against pathogens. The innovative antihyperglycaemic agents glucagon-like peptide 1 (GLP-1) receptor agonists and sodium-glucose cotransporter 2 (SGLT2) inhibitors decrease bodyweight and have the potential to counter low-grade inflammation. These key activities could rewire two components of the life history theory operative in adulthood-ie, maintenance and defence. In this Personal View, we postulate that the benefits of these medications on the cardiovascular system, beyond their glucose-lowering effects, could be mediated by the reduction of the maintenance cost driven by obesity and efforts spent on blunting low-grade inflammation.

Rethinking water, sanitation, and hygiene for human growth and development

Life history theory emphasises plasticity in developmental and biological programming where conditions in early life, lead to long-term consequences for health and wellbeing. Studies linking water, sanitation, and hygiene, nutrition, and child growth and development have emphasised the optimisation of linear growth as a key metric for the evaluation of intervention efficacy. Life history characteristics pertaining to human growth and phenotypic plasticity, suggest that different developmental outcomes in early childhood may be responsive to different stimuli at different ages. Energy utilisation by the human brain, from birth through childhood, accounts for a disproportionate percentage of the resting metabolic rate. Undernutrition in early life, and its relative resultant energy deficiency, may trigger adaptive physiological mechanisms prioritising brain growth at the expense of body growth. Emphasis placed on linear growth may have impeded the significance of WASH due to excluding aspects of child development beyond height/weight. We propose that incorporating evolutionary public health and life history theory perspectives, allows for the identification of age-appropriate biological outcomes and WASH indicators, while anticipating the timing and life-course suitability of the interventions being operationalised. Finally, integrating reflections regarding context allows for the development of transformative WASH interventions.

A Breastfeeding Relaxation Intervention Promotes Growth in Late Preterm and Early Term Infants: Results from a Randomized Controlled Trial

Breastfeeding involves signaling between mother and offspring through biological (breast milk) and behavioral pathways. This study tested this by examining the effects of a relaxation intervention in an understudied infant population. Breastfeeding mothers of late preterm (34^0/7-36^6/7 weeks) and early term (37^0/7-38^6/7 weeks) infants were randomized to the relaxation group (RG, n = 35), where they were asked to listen to a meditation recording while breastfeeding from 3 weeks post-delivery, or the control group (CG, n = 37) where no intervention was given. Primary outcomes-maternal stress and infant weight-were assessed at 2-3 (baseline) and 6-8 weeks post-delivery. Secondary outcomes included infant length, infant behavior, maternal verbal memory, salivary cortisol, and breast milk composition. Infants in the RG had significantly higher change in weight-for-age Z-score compared to those in CG (effect size: 0.4; 95% CI: 0.09, 0.71; p = 0.01), and shorter crying duration [RG: 5.0 min, 0.0-120.0 vs. CG: 30.0 min, 0.0-142.0; p = 0.03]. RG mothers had greater reduction in cortisol (effect size: -0.08 ug/dL, 95% CI -0.15, -0.01; p = 0.03) and better maternal verbal learning score (effect size: 1.1 words, 95% CI 0.04, 2.1; p = 0.04) than CG mothers, but did not differ in stress scores. A simple relaxation intervention during breastfeeding could be beneficial in promoting growth of late preterm and early term infants. Further investigation of other potential biological and behavioral mediators is warranted.

Great tits differ in glucocorticoid plasticity in response to spring temperature

Fluctuations in environmental temperature affect energy metabolism and stimulate the expression of reversible phenotypic plasticity in vertebrate behavioural and physiological traits. Changes in circulating concentrations of glucocorticoid hormones often underpin environmentally induced phenotypic plasticity. Ongoing climate change is predicted to increase fluctuations in environmental temperature globally, making it imperative to determine the standing phenotypic variation in glucocorticoid responses of free-living populations to evaluate their potential for coping via plastic or evolutionary changes. Using a reaction norm approach, we repeatedly sampled wild great tit (Parus major) individuals for circulating glucocorticoid concentrations during reproduction across five years to quantify individual variation in glucocorticoid plasticity along an environmental temperature gradient. As expected, baseline and stress-induced glucocorticoid concentrations increased with lower environmental temperatures at the population and within-individual level. Moreover, we provide unique evidence that individuals differ significantly in their plastic responses to the temperature gradient for both glucocorticoid traits, with some displaying greater plasticity than others. Average concentrations and degree of plasticity covaried for baseline glucocorticoids, indicating that these two reaction norm components are linked. Hence, individual variation in glucocorticoid plasticity in response to a key environmental factor exists in a wild vertebrate population, representing a crucial step to assess their potential to endure temperature fluctuations.

Integrating economic and evolutionary approaches to polygynous marriage

We outline the potential for integrating economic and evolutionary approaches to marriage and the family. Our broad argument is that the approaches share a concern for competition. Evolutionary scholars are concerned with the fitness consequences of competition and economists are centrally concerned with the nature of competition: how the allocation of scarce resources is mediated by potentially complex forms of social interaction and conflicts of interest. We illustrate our argument by focusing on conceptual and empirical approaches to a topic of interest to economists and evolutionary scholars: polygynous marriage. In comparing conceptual approaches, we distinguish between those that emphasise the physical environment and those that emphasise the social environment. We discuss some advantages of analysing marriage through the lens of competitive markets, and outline some of the ways that economists analyse the emergence of rules governing the family. In discussing empirical approaches to polygynous marriage, we describe how a concern for informing contemporary policy leads economists to focus on the consequences of polygyny, and in particular we describe some of the ways in which economists attempt to distinguish causal effects from selection effects.

Schizophrenia: the new etiological synthesis

Schizophrenia has been an evolutionary paradox: it has high heritability, but it is associated with decreased reproductive success. The causal genetic variants underlying schizophrenia are thought to be under weak negative selection. To unravel this paradox, many evolutionary explanations have been suggested for schizophrenia. We critically discuss the constellation of evolutionary hypotheses for schizophrenia, highlighting the lack of empirical support for most existing evolutionary hypotheses-with the exception of the relatively well supported evolutionary mismatch hypothesis. It posits that evolutionarily novel features of contemporary environments, such as chronic stress, low-grade systemic inflammation, and gut dysbiosis, increase susceptibility to schizophrenia. Environmental factors such as microbial infections (e.g., Toxoplasma gondii) can better predict the onset of schizophrenia than polygenic risk scores. However, researchers have not been able to explain why only a small minority of infected people develop schizophrenia. The new etiological synthesis of schizophrenia indicates that an interaction between host genotype, microbe infection, and chronic stress causes schizophrenia, with neuroinflammation and gut dysbiosis mediating this etiological pathway. Instead of just alleviating symptoms with drugs, the parasite x genotype x stress model emphasizes that schizophrenia treatment should focus on detecting and treating possible underlying microbial infection(s), neuroinflammation, gut dysbiosis, and chronic stress.

Association of growth patterns during infancy and puberty with lung function, wheezing and asthma in adolescents aged 17.5 years: evidence from ‘Children of 1997’ Hong Kong Chinese Birth Cohort

Background

Rapid growth is related to adverse respiratory outcomes although possibly confounded or limited by growth modelling methods. We investigated the association of infant and pubertal growth with lung function, wheezing and asthma in a non-Western setting.

Methods

In Hong Kong’s ‘Children of 1997’ Chinese birth cohort (n = 8327), weight during infancy and weight, height and body mass index (BMI) during puberty were modelled using a super-imposition by translation and rotation model to identify (larger or smaller) size, (earlier or later) tempo and (slower or faster) velocity. Sex-specific associations with forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1/FVC (Global Lung function Initiative z-score) and self-reported wheezing and asthma at ∼17.5 years were assessed.

Results

For each fraction higher than average weight growth velocity during infancy, FVC was higher in boys (0.90 SD, 95% CI 0.35; 1.44) and girls (0.77 SD, 95% CI 0.24; 1.30), FEV1/FVC was lower (–0.74 SD, 95% CI –1.38; –0.10) and wheezing was higher (odds ratio 6.92, 95% CI 1.60; 29.99) in boys and an inverse association with FVC was observed for tempo but not for size. Associations for weight growth velocity in puberty were similar but weaker. Greater size and higher velocity of BMI growth was associated with higher FVC, lower FEV1/FVC and higher asthma and wheezing risk.

Conclusion

Accelerated infant and pubertal weight growth were associated with disproportionate lung size and airway growth, and higher risk of asthma; optimizing early-life growth patterns could be important.

Life history trade-offs associated with exposure to low maternal capital are different in sons compared to daughters: Evidence from a prospective Brazilian birth cohort

Background

Environmental exposures in early life explain variability in many physiological and behavioural traits in adulthood. Recently, we showed that exposure to a composite marker of low maternal capital explained the clustering of adverse behavioural and physical traits in adult daughters in a Brazilian birth cohort. These associations were strongly mediated by whether or not the daughter had reproduced by the age of 18 years. Using evolutionary life history theory, we attributed these associations to trade-offs between competing outcomes, whereby daughters exposed to low maternal capital prioritised investment in reproduction and defence over maintenance and growth. However, little is known about such trade-offs in sons.

Methods

We investigated 2,024 mother-son dyads from the same birth cohort. We combined data on maternal height, body mass index, income, and education into a composite "maternal capital" index. Son outcomes included reproductive status at the age of 18 years, growth trajectory, adult anthropometry, body composition, cardio-metabolic risk, educational attainment, work status, and risky behaviour (smoking, violent crime). We tested whether sons' early reproduction and exposure to low maternal capital were associated with adverse outcomes and whether this accounted for the clustering of adverse outcomes within individuals.

Results

Sons reproducing early were shorter, less educated, and more likely to be earning a salary and showing risky behaviour compared to those not reproducing, but did not differ in foetal growth. Low maternal capital was associated with a greater likelihood of sons' reproducing early, leaving school, and smoking. High maternal capital was positively associated with sons' birth weight, adult size, and staying in school. However, the greater adiposity of high-capital sons was associated with an unhealthier cardio-metabolic profile.

Conclusion

Exposure to low maternal investment is associated with trade-offs between life history functions, helping to explain the clustering of adverse outcomes in sons. The patterns indicated future discounting, with reduced maternal investment associated with early reproduction but less investment in growth, education, or healthy behaviour. However, we also found differences compared to our analyses of daughters, with fewer physical costs associated with early reproduction. Exposure to intergenerational "cycles of disadvantage" has different effects on sons vs. daughters, hence interventions may have sex-specific consequences.

Locus-level antagonistic selection shaped the polygenic architecture of human complex diseases

BACKGROUND

We aimed to evaluate the potential role of antagonistic selection in polygenic diseases: if one variant increases the risk of one disease and decreases the risk of another disease, the signals of genetic risk elimination by natural selection will be distorted, which leads to a higher frequency of risk alleles.

METHODS

We applied local genetic correlations and transcriptome-wide association studies to identify genomic loci and genes adversely associated with at least two diseases. Then, we used different population genetic metrics to measure the signals of natural selection for these loci and genes.

RESULTS

First, we identified 2120 cases of antagonistic pleiotropy (negative local genetic correlation) among 87 diseases in 716 genomic loci (antagonistic loci). Next, by comparing with non-antagonistic loci, we observed that antagonistic loci explained an excess proportion of disease heritability (median 6%), showed enhanced signals of balancing selection, and reduced signals of directional polygenic adaptation. Then, at the gene expression level, we identified 31,991 cases of antagonistic pleiotropy among 98 diseases at 4368 genes. However, evidence of altered signals of selection pressure and heritability distribution at the gene expression level is limited.

CONCLUSION

We conclude that antagonistic pleiotropy is widespread among human polygenic diseases, and it has distorted the evolutionary signal and genetic architecture of diseases at the locus level.

Encouraging COVID-19 vaccination via an evolutionary theoretical approach: A randomized controlled study in Japan

OBJECTIVE

We aimed to examine the effect of a message that target the fundamental human motive of kin care on COVID-19 vaccination recommendations among participants with young children, based on an evolutionary theoretical approach.

METHODS

Participants with young children (n = 969) were randomly assigned either to a group that received an intervention message that targeted the fundamental motive of kin care, or that targeted the fundamental motive of disease avoidance, or a control message. Intention to receive COVID-19 vaccination was assessed both before and after reading the messages. A one-way ANOVA with Tukey's or Games-Howell test was conducted.

RESULTS

An intervention message targeting the fundamental motive of kin care and disease avoidance significantly increased intention of vaccination versus a control message (p < 0.001, respectively).

CONCLUSION

The evolutionary theoretical approach that focuses on fundamental human motives has the potential to extend the communication strategy for COVID-19 vaccination recommendations.

PRACTICE IMPLICATIONS

Health professionals should deliver messages that target the fundamental motive of kin care as well as messages about the susceptibility and severity of COVID-19 and vaccine efficacy (e.g., "Get vaccinated against COVID-19 for your child's sake, because if you are infected, you will be unable to care for your child.").

An Evolutionary Model of “Sexual Conflict” Over Women's Age at Marriage: Implications for Child Mortality and Undernutrition

Background

Early women's marriage is associated with adverse outcomes for mothers and their offspring, including reduced human capital and increased child undernutrition and mortality. Despite preventive efforts, it remains common in many populations and is often favored by cultural norms. A key question is why it remains common, given such penalties. Using an evolutionary perspective, a simple mathematical model was developed to explore women's optimal marriage age under different circumstances, if the sole aim were to maximize maternal or paternal lifetime reproductive fitness (surviving offspring).

Methods

The model was based on several assumptions, supported by empirical evidence, regarding relationships between women's marital age and parental and offspring outcomes. It assumes that later marriage promotes women's autonomy, enhancing control over fertility and childcare, but increases paternity uncertainty. Given these assumptions, optimal marriage ages for maximizing maternal and paternal fitness were calculated. The basic model was then used to simulate environmental changes or public health interventions, including shifts in child mortality, suppression of women's autonomy, or promoting women's contraception or education.

Results

In the basic model, paternal fitness is maximized at lower women's marriage age than is maternal fitness, with the paternal optimum worsening child undernutrition and mortality. A family planning intervention delays marriage age and reduces child mortality and undernutrition, at a cost to paternal but not maternal fitness. Reductions in child mortality favor earlier marriage but increase child undernutrition, whereas ecological shocks that increase child mortality favor later marriage but reduce fitness of both parents. An education intervention favors later marriage and reduces child mortality and undernutrition, but at a cost to paternal fitness. Efforts to suppress maternal autonomy substantially increase fitness of both parents, but only if other members of the household provide compensatory childcare.

Conclusion

Early women's marriage maximizes paternal fitness despite relatively high child mortality and undernutrition, by increasing fertility and reducing paternity uncertainty. This tension between the sexes over the optimal marriage age is sensitive to ecological stresses or interventions. Education interventions seem most likely to improve maternal and child outcomes, but may be resisted by males and their kin as they may reduce paternal fitness.

Encouragement of cervical cancer screening via an evolutionary theoretical approach: A randomized controlled study in Japan

The introduction of an evolutionary perspective into public health research has received attention in recent years. We aimed to examine the effects of messages that target the fundamental human motive of kin care (i.e., childbirth and parenting) on cervical cancer screening recommendations, based on an evolutionary theoretical approach. A randomized controlled study was conducted in Japan. Female participants (n = 969) were randomly assigned either to a group that received an intervention message that targeted the fundamental motive of kin care (recommending cervical cancer screening for future childbearing), or that targeted the fundamental motive of disease avoidance, or a control message. Intention to obtain cervical cancer screening was assessed both before and after reading the messages. A one-way ANOVA with Tukey's or Games-Howell test was conducted. Each of the intervention message targeting the fundamental motive of kin care and of the message targeting disease avoidance significantly increased intention to obtain cervical cancer screening versus a control message (M = 0.76 vs. M = 0.17, p < 0.001; M = 0.74 vs. M = 0.17, p < 0.001, respectively). A message that targeted the fundamental motive of kin care was as effective as one targeting the fundamental motive of disease avoidance. Health professionals should add messages that target the fundamental motive of kin care to their repertoire to encourage cervical cancer screening among women who wish future childbirth and parenting (e.g., "Delayed detection of cervical cancer may prevent your future childbirth and parenting. So let's obtain cervical cancer screening regularly for your future childbirth and parenting.").

Inferring Signatures of Positive Selection in Whole-Genome Sequencing Data: An Overview of Haplotype-Based Methods

Signatures of positive selection in the genome are a characteristic mark of adaptation that can reveal an ongoing, recent, or ancient response to environmental change throughout the evolution of a population. New sources of food, climate conditions, and exposure to pathogens are only some of the possible sources of selective pressure, and the rise of advantageous genetic variants is a crucial determinant of survival and reproduction. In this context, the ability to detect these signatures of selection may pinpoint genetic variants that are responsible for a significant change in gene regulation, gene expression, or protein synthesis, structure, and function. This review focuses on statistical methods that take advantage of linkage disequilibrium and haplotype determination to reveal signatures of positive selection in whole-genome sequencing data, showing that they emerge from different descriptions of the same underlying event. Moreover, considerations are provided around the application of these statistics to different species, their suitability for ancient DNA, and the usefulness of discovering variants under selection for biomedicine and public health in an evolutionary medicine framework.

Encouraging HPV Vaccination via an Evolutionary Theoretical Approach: A Randomized Controlled Study in Japan

In recent years, researchers have discussed the introduction of an evolutionary perspective into public health and health behavior research. We aimed to examine the effects of messages that target the fundamental human motive of kin care on HPV vaccination recommendations among mothers with daughters, based on an evolutionary theoretical approach. This study consisted of a three-arm parallel-group single-blinded randomized controlled study. A web-based survey was conducted from 7 to 8 October 2021 in Japan. Mothers with daughters (n = 969) were randomly assigned either to a group that received an intervention message that targeted the fundamental motive of kin care, or that targeted the fundamental motive of disease avoidance, or a control message. Intention to have daughter(s) receive HPV vaccination was assessed both before and right after reading the messages. A one-way ANOVA with Tukey’s or Games−Howell test was conducted. An intervention message targeting the fundamental motive of kin care and disease avoidance significantly increased intention of vaccination versus a control message (p < 0.001, respectively). There was no significant difference between the two intervention groups. The evolutionary theoretical approach that focuses on fundamental human motives may have the potential to extend the communication strategy for HPV vaccination recommendations. Health professionals may be recommended to deliver messages that target the fundamental motive of kin care as well as messages about the susceptibility and severity of cervical cancer and vaccine efficacy (e.g., “Getting cervical cancer can prevent childbirth. To protect your daughter and your future grandchildren, get your daughter vaccinated against HPV”). However, the present study only evaluated HPV vaccination intentions in Japanese mothers with daughters. Future studies should evaluate vaccination behavior in a wider range of subjects to confirm that the evolutionary theoretical approach promotes HPV vaccination.

Genetic validation of neurokinin 3 receptor antagonists for ischemic heart disease prevention in men – A one-sample Mendelian randomization study

Background

Ischemic heart disease (IHD) is a leading cause of mortality, particularly for men. Few interventions have focused on protecting specifically men. Emerging evidence may implicate testosterone. Neurokinin 3 receptor (NK3R) antagonists, an existing class of drugs being considered as treatments for reproductive conditions in women, affect testosterone; this study addresses genetic validation of their use to prevent IHD in men.

Methods

A one-sample Mendelian randomization (MR) study using the UK Biobank cohort study, based on independent (r² < 0.005) genetic variants predicting testosterone in men (n = 157738) at genome wide significance in the target gene for NK3R antagonists (TACR3), was used to assess associations with IHD (cases=15056, non-cases=151964) and positive control outcomes (relative age voice broke, children fathered, hypertension) in men and a negative control outcome (IHD) in women using summary statistics. A two-sample MR study using the PRACTICAL consortium was used for the positive control outcome of prostate cancer.

Findings

Two relevant TACR3 genetic variants (rs116646027 and rs1351623) were identified in men. Genetically mimicked NK3R antagonists were inversely associated with IHD (odds ratio 0.54 per standard deviation lower testosterone, 95% confidence interval 0.31, 0.94) and with control outcomes (older relative age voice broke, fewer children and lower risk of hypertension and prostate cancer) as expected in men and in women (unrelated to IHD).

Interpretation

Genetic validation of a role of NK3R antagonists in IHD suggests their consideration as a new means of preventing IHD in men. Whether they protect against prostate cancer might bear further consideration.

A growth area: A review of the value of clinical studies of child growth for palaeopathology

Studies of living children demonstrate that early life stress impacts linear growth outcomes. Stresses affecting linear growth may also impact later life health outcomes, including increased cardiometabolic disease risk. Palaeopathologists also assess the growth of children recovered from bioarchaeological contexts. Early life stresses are inferred to affect linear growth outcomes, and measurements of skeletal linear dimensions alongside other bioarchaeological information may indicate the types of challenges faced by past groups. In clinical settings, the impacts of stress on growing children are typically measured by examining height. Palaeopathologists are limited to examining bone dimensions directly and must grapple with incomplete pictures of childhood experiences that may affect growth. Palaeopathologists may use clinical growth studies to inform observations among past children; however, there may be issues with this approach. Here, we review the relationship between contemporary and palaeopathological studies of child and adolescent growth. We identify approaches to help bridge the gap between palaeopathological and biomedical growth studies. We advocate for: the creation of bone-specific growth reference information using medical imaging and greater examination of limb proportions; the inclusion of children from different global regions and life circumstances in contemporary bone growth studies; and greater collaboration and dialogue between palaeopathologists and clinicians as new studies are designed to assess linear growth past and present. We advocate for building stronger bridges between these fields to improve interpretations of growth patterns across human history and to potentially improve interventions for children living and growing today.

A Life History Perspective on Athletes with Low Energy Availability

The energy costs of athletic training can be substantial, and deficits arising from costs unmet by adequate energy intake, leading to a state of low energy availability, may adversely impact athlete health and performance. Life history theory is a branch of evolutionary theory that recognizes that the way the body uses energy-and responds to low energy availability-is an evolved trait. Energy is a finite resource that must be distributed throughout the body to simultaneously fuel all biological processes. When energy availability is low, insufficient energy may be available to equally support all processes. As energy used for one function cannot be used for others, energetic "trade-offs" will arise. Biological processes offering the greatest immediate survival value will be protected, even if this results in energy being diverted away from others, potentially leading to their downregulation. Athletes with low energy availability provide a useful model for anthropologists investigating the biological trade-offs that occur when energy is scarce, while the broader conceptual framework provided by life history theory may be useful to sport and exercise researchers who investigate the influence of low energy availability on athlete health and performance. The goals of this review are: (1) to describe the core tenets of life history theory; (2) consider trade-offs that might occur in athletes with low energy availability in the context of four broad biological areas: reproduction, somatic maintenance, growth, and immunity; and (3) use this evolutionary perspective to consider potential directions for future research.

Inflammatory markers as correlates of body composition and grip strength among adults with and without HIV: A cross-sectional study in Ethiopia

BACKGROUND

Changes in body composition and muscle strength are common among individuals with HIV. We investigated the associations of inflammation with body composition and grip strength in adults with and without HIV.

METHODS

Cross-sectional study among Ethiopian treatment-naïve individuals with and without HIV. Fat mass and fat-free mass adjusted for height (kg/m²) were used as indicators of body composition.

RESULTS

288/100 individuals with/without HIV were included between July 2010 and August 2012. Females with HIV had lower fat mass index (FMI) and fat-free mass index (FFMI) than females without HIV, whereas no difference was seen between males with and without HIV. Males and females with HIV had lower grip strength than their counterparts without HIV. Serum alpha-1-acid glycoprotein (s-AGP) was negatively correlated with FMI (-0.71 kg/m², 95% CI: -1.2; -0.3) among individuals with HIV, and those with HIV and serum C-reactive protein (s-CRP) ≥ 10 mg/l had 0.78 kg/m² (95% CI -1.4; -0.2) lower FMI than those with s-CRP < 10 mg/l. In contrast, s-AGP was positively correlated with FMI (2.09 kg/m², 95% CI 0.6; 3.6) in individuals without HIV. S-CRP and AGP were negatively associated with grip strength in individuals with HIV, while no correlation was observed among those without HIV.

CONCLUSION

Inflammation was positively associated with FMI in individuals without HIV while it was negatively associated with FMI in those with HIV, indicating that inflammation may be one of the drivers of depleting energy reserves among treatment-naïve individuals with HIV. Inflammation was associated with decreased muscle quantity and functional capacity among individuals with HIV, but not in those without HIV.

Alternative Metabolic Strategies are Employed by Endurance Runners of Different Body Sizes; Implications for Human Evolution

Objective

A suite of adaptations facilitating endurance running (ER) evolved within the hominin lineage. This may have improved our ability to reach scavenging sites before competitors, or to hunt prey over long distances. Running economy (RE) is a key determinant of endurance running performance, and depends largely on the magnitude of force required to support body mass. However, numerous environmental factors influence body mass, thereby significantly affecting RE. This study tested the hypothesis that alternative metabolic strategies may have emerged to enable ER in individuals with larger body mass and poor RE.

Methods

A cohort of male (n = 25) and female (n = 19) ultra-endurance runners completed submaximal and exhaustive treadmill protocols to determine RE, and V̇O2Max.

Results

Body mass was positively associated with sub-maximal oxygen consumption at both LT1 (male r=0.66, p<0.001; female LT1 r=0.23, p=0.177) and LT2 (male r=0.59, p=0.001; female r=0.23, p=0.183) and also with V̇O2Max (male r=0.60, p=0.001; female r=0.41, p=0.046). Additionally, sub-maximal oxygen consumption varied positively with V̇O2Max in both male (LT1 r=0.54, p=0.003; LT2 r=0.77, p<0.001) and female athletes (LT1 r=0.88, p<0.001; LT2 r=0.92, p<0.001).

Conclusions

The results suggest that, while individuals with low mass and good RE can glide economically as they run, larger individuals can compensate for the negative effects their mass has on RE by increasing their capacity to consume oxygen. The elevated energy expenditure of this low-economy high-energy turnover approach to ER may bring costs associated with energy diversion away from other physiological processes, however.

Impact of Multimorbidity on Symptoms of Depression, Anxiety, and Stress in Older Adults: Is There a Sex Difference?

Introduction: Multimorbidity has become a key issue in the health care sector globally, and it can also lead to psychological distress in older adults. This study aimed to assess the impact of multimorbidity on depression, anxiety, and stress symptoms and identify whether there is a sex difference in these associations.

Methods: A cross-sectional study using a multistage random sampling method was conducted among 3,266 older adults in China. Multiple linear regression models were used to estimate the independent associations between multimorbidity and depression, anxiety, and stress symptoms. Furthermore, interaction analysis was employed to investigate the interaction effect of multimorbidity and sex on depression, anxiety, and stress symptoms.

Results: A total of 3,250 participants aged 60 years and older were included in this study. Our findings suggest that multimorbidity is strongly positively associated with depression, anxiety, and stress symptoms. In addition, the positive relations between multimorbidity and depression, anxiety, and stress symptoms are stronger for older female than male adults.

Conclusion: Old adults with multimorbidity are more likely have depression, anxiety, and stress symptoms. This study offers new insight for the mental health from the perspective of multimorbidity among older people, implies that encouraging the accessibility of treatment for multimorbidity in older people with different sex may be effective in promoting mental health in China.

Epigenetic regulation of 5α reductase-1 underlies adaptive plasticity of reproductive function and pubertal timing

Background

Women facing increased energetic demands in childhood commonly have altered adult ovarian activity and shorter reproductive lifespan, possibly comprising a strategy to optimize reproductive success. Here, we sought to understand the mechanisms of early-life programming of reproductive function, by integrating analysis of reproductive tissues in an appropriate mouse model with methylation analysis of proxy tissue DNA in a well-characterized population of Bangladeshi migrants in the UK. Bangladeshi women whose childhood was in Bangladesh were found to have later pubertal onset and lower age-matched ovarian reserve than Bangladeshi women who grew-up in England. Subsequently, we aimed to explore the potential relevance to the altered reproductive phenotype of one of the genes that emerged from the screens.

Results

Of the genes associated with differential methylation in the Bangladeshi women whose childhood was in Bangladesh as compared to Bangladeshi women who grew up in the UK, 13 correlated with altered expression of the orthologous gene in the mouse model ovaries. These mice had delayed pubertal onset and a smaller ovarian reserve compared to controls. The most relevant of these genes for reproductive function appeared to be SRD5A1, which encodes the steroidogenic enzyme 5α reductase-1. SRD5A1 was more methylated at the same transcriptional enhancer in mice ovaries as in the women’s buccal DNA, and its expression was lower in the hypothalamus of the mice as well, suggesting a possible role in the central control of reproduction. The expression of Kiss1 and Gnrh was also lower in these mice compared to controls, and inhibition of 5α reductase-1 reduced Kiss1 and Gnrh mRNA levels and blocked GnRH release in GnRH neuronal cell cultures. Crucially, we show that inhibition of this enzyme in female mice in vivo delayed pubertal onset.

Conclusions

SRD5A1/5α reductase-1 responds epigenetically to the environment and its downregulation appears to alter the reproductive phenotype. These findings help to explain diversity in reproductive characteristics and how they are shaped by early-life environment and reveal novel pathways that might be targeted to mitigate health issues caused by life-history trade-offs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01219-6.

Biosocial life-course factors associated with women's early marriage in rural India: The prospective longitudinal Pune Maternal Nutrition Study

OBJECTIVES

By convention, women's early marriage is considered a sociocultural decision sensitive to factors acting during adolescence such as poverty, early menarche, and less education. Few studies have examined broader risk factors in the natal household prior to marriage. We investigated whether biosocial markers of parental investment through the daughters' life-course were associated with early marriage risk in rural India. We used an evolutionary perspective to interpret our findings.

MATERIALS AND METHODS

A prospective cohort recruited mothers at preconception. Children were followed from birth to age 21 years. Multivariable logistic regression models estimated odds ratios of marrying early (<19 years) associated first with wealth, age at menarche and education, and then with broader markers of maternal phenotype, natal household characteristics, and girls' growth trajectories. Models adjusted for confounders.

RESULTS

Of 305 girls, 71 (23%) had married early. Early married girls showed different patterns of growth compared to unmarried girls. Neither poverty nor early menarche predicted early marriage. Girls' non-completion of lower secondary school predicted early marriage, explaining 19% of the variance. Independent of girls' lower schooling, nuclear household, low paternal education, shorter gestation, and girls' poor infant weight gain were associated with marrying early, explaining in combination 35% of the variance.

DISCUSSION

Early marriage reflects "future discounting," where reduced parental investment in daughters' somatic and educational capital from early in her life favors an earlier transition to the life-course stage when reproduction can occur. Interventions initiated in adolescence may occur too late in the life-course to effectively delay women's marriage.

Demography and the rise, apparent fall, and resurgence of eugenics

Demography was heavily involved in the eugenics movement of the early twentieth century but, along with most other social science disciplines, largely rejected eugenic thinking in the decades after the Second World War. Eugenic ideology never entirely deserted academia, however, and in the twenty-first century, it is re-emerging into mainstream academic discussion. This paper aims, first, to provide a reminder of demography's early links with eugenics and, second, to raise awareness of this academic resurgence of eugenic ideology. The final aim of the paper is to recommend ways to counter this resurgence: these include more active discussion of demography's eugenic past, especially when training students; greater emphasis on critical approaches in demography; and greater engagement of demographers (and other social scientists) with biologists and geneticists, in order to ensure that research which combines the biological and social sciences is rigorous.

A selection pressure landscape for 870 human polygenic traits

Characterizing the natural selection of complex traits is important for understanding human evolution and both biological and pathological mechanisms. We leveraged genome-wide summary statistics for 870 polygenic traits and attempted to quantify signals of selection on traits of different forms in European ancestry across four periods in human history and evolution. We found that 88% of these traits underwent polygenic change in the past 2,000-3,000 years. Recent selection was associated with ancient selection signals in the same trait. Traits related to pigmentation, body measurement and nutritional intake exhibited strong selection signals across different time scales. Our findings are limited by our use of exclusively European data and the use of genome-wide association study data, which identify associations between genetic variants and phenotypes that may not be causal. In sum, we provide an overview of signals of selection on human polygenic traits and their characteristics across human evolution, based on a European subset of human genetic diversity. These findings could serve as a foundation for further populational and medical genetic studies.

How do reproduction, parenting, and health cluster together? Exploring diverging destinies, life histories and weathering in two UK cohort studies

Life history theory researchers often assume reproductive, parenting and health behaviours pattern across a fast-slow continuum, with 'fast' life histories (typified by short lifespans, early maturation and investing in quantity over quality of children) favoured in poor quality environments and/or when resources are scarce. Some researchers further reduce this down to a simplistic 'fast' versus 'slow' dichotomy. Some of these ideas, with different theoretical motivations, are echoed in the 'diverging destinies' and 'weathering' frameworks developed in the social sciences. Whether clustering of reproductive, parenting and health traits exists has rarely been empirically tested, however. Using latent class analysis on data on mothers from the UK's Millennium Cohort (MCS) and Born in Bradford (BiB) studies, we explored whether reproduction and parenting traits clustered into 'diverging destinies', whether 'weathering' effects tied together health and reproduction, and whether all three domains were combined into either 'fast' vs 'slow' life histories, or into three groups more indicative of a fast-slow continuum. We leveraged ethnic diversity in these samples to examine four groups of mothers separately: 1. MCS White British/Irish (n = 15,423); 2. MCS Pakistani-origin (n = 923); 3. BiB White British (n = 3937); 4. BiB Pakistani-origin (n = 4351), and explored whether faster 'weathering' was evident amongst Pakistani-origin mothers. Both two and three class models emerged as potential descriptions of latent subgroups, potentially providing support for fast and slow life histories or a continuum of traits. However, response profiles provided only limited support for theoretical predictions of which traits should cluster together, with inconsistent and restricted clustering of traits both within and between the domains of reproduction, parenting, and health. In addition, trait clustering was more pronounced amongst White mothers and we found no clear evidence supporting faster 'weathering' amongst Pakistani-origin mothers; the observed clustering instead suggested that cultural constraints may influence linkages between traits. Our results therefore provide some limited support for models which suggest certain traits cluster together in predictable ways, but it is also clear that theoretical frameworks should not emphasise very rigid clustering of large numbers of traits and should allow for contextual influences on clustering.

Effect of Basal Metabolic Rate on Cancer: A Mendelian Randomization Study

Background: Basal metabolic rate is associated with cancer, but these observations are open to confounding. Limited evidence from Mendelian randomization studies exists, with inconclusive results. Moreover, whether basal metabolic rate has a similar role in cancer for men and women independent of insulin-like growth factor 1 increasing cancer risk has not been investigated.

Methods: We conducted a two-sample Mendelian randomization study using summary data from the UK Biobank to estimate the causal effect of basal metabolic rate on cancer. Overall and sex-specific analysis and multiple sensitivity analyses were performed including multivariable Mendelian randomization to control for insulin-like growth factor 1.

Results: We obtained 782 genetic variants strongly (p-value < 5 × 10^–8) and independently (r² < 0.01) predicting basal metabolic rate. Genetically predicted higher basal metabolic rate was associated with an increase in cancer risk overall (odds ratio, 1.06; 95% confidence interval, 1.02–1.10) with similar estimates by sex (odds ratio for men, 1.07; 95% confidence interval, 1.002–1.14; odds ratio for women, 1.06; 95% confidence interval, 0.995–1.12). Sensitivity analyses including adjustment for insulin-like growth factor 1 showed directionally consistent results.

Conclusion: Higher basal metabolic rate might increase cancer risk. Basal metabolic rate as a potential modifiable target of cancer prevention warrants further study.

Investigating the association of testosterone with survival in men and women using a Mendelian randomization study in the UK Biobank

Life expectancy in the developed West is currently stagnated and remains shorter in men than women. Well-established evolutionary biology theory suggests lifespan trades-off against reproductive success, possibly sex-specifically. We examined whether a key driver of reproductive success, testosterone, affected survival using a Mendelian randomization longevity study in the UK Biobank to obtain unbiased estimates, along with control exposures. We applied published genetic instruments for testosterone to obtain inverse variance weighted estimates of associations with survival to (i.e., age at) recruitment, in 167,020 men and 194,174 women. We similarly obtained estimates for a positive control (smoking initiation), and a negative control (absorbate), a marker of vitamin C metabolism. Testosterone was associated with poorer survival (0.10 years younger at recruitment per effect size of testosterone, 95% confidence interval (CI) 0.004 to 0.20). As expected, smoking initiation was also associated with poorer survival (0.37 years younger, 95% CI 0.25 to 0.50), but not absorbate (0.01 years younger, 95% CI - 0.09 to 0.11). Several aspects of a healthy lifestyle (low animal fat diet) and several widely used medications (statins, metformin, dexamethasone and possibly aspirin) may modulate testosterone. Explicitly designing interventions sex-specifically based on these insights might help address stagnating life expectancy and sexual disparities.

Polygenic and major-locus contributions to sexual maturation timing in Atlantic salmon

Sexual maturation timing is a life-history trait central to the balance between mortality and reproduction. Maturation may be triggered when an underlying compound trait, called liability, exceeds a threshold. In many different species and especially fishes, this liability is approximated by growth and body condition. However, environmental vs. genetic contributions either directly or via growth and body condition to maturation timing remain unclear. Uncertainty exists also because the maturation process can reverse this causality and itself affect growth and body condition. In addition, disentangling the contributions of polygenic and major loci can be important. In many fishes, males mature before females, enabling the study of associations between male maturation and maturation-unbiased female liability traits. Using 40 Atlantic salmon families, longitudinal common-garden experimentation, and quantitative genetic analyses, we disentangled environmental from polygenic and major locus (vgll3) effects on male maturation, and sex-specific growth and condition. We detected polygenic heritabilities for maturation, growth, and body condition, and vgll3 effects on maturation and body condition but not on growth. Longitudinal patterns for sex-specific phenotypic liability, and for genetic variances and correlations between sexes suggested that early growth and condition indeed positively affected maturation initiation. However, towards spawning time, causality appeared reversed for males whereby maturation affected growth negatively and condition positively via both the environmental and genetic effects. Altogether, the results indicate that growth and condition are useful traits to study liability for maturation initiation, but only until maturation alters their expression, and that vgll3 contributes to maturation initiation via condition.

Race and genetics versus 'race' in genetics: A systematic review of the use of African ancestry in genetic studies

Social scientists have long understood race to be a social category invented to justify slavery and evolutionary biologists know the socially constructed racial categories do not align with our biological understanding of genetic variation. The completion of the Human Genome Project in 2003 confirmed humans are 99.9% identical at the DNA level and there is no genetic basis for race. A systematic review of the PubMed medical literature published since 2003 was conducted to assess the use of African ancestry to denote study populations in genetic studies categorized as clinical trials, to examine the stated rationale for its use and to assess the use of evolutionary principles to explain human genetic diversity. We searched for papers that included the terms 'African', 'African American' or 'Black' in studies of behavior (20 papers), physiological responses, the pharmacokinetics of drugs and/or disease associations (62 papers), and as a genetic category in studies, including the examination of genotypes associated with life stress, pain, stuttering and drug clearance (126 papers). Of these, we identified 74 studies in which self-reported race alone or in combination with admixture mapping was used to define the study population. However, none of these studies provided a genetic explanation for the use of the self-identified race as a genetic category and only seven proffered evolutionary explanations of their data. The concept of continuous genetic variation was not clearly articulated in any of these papers, presumably due to the paucity of evolutionary science in the college and medical school curricula.

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 = 0.15–0.53) with a range of psychological variables, stressors, and health outcomes (depressive symptoms [n = 670], social conflicts [n = 401], non-social problems [n = 398], social support [n = 399], cortisol [n = 811], body mass index [n = 9,926], blood pressure [n = 3,195], self-rated health [n = 2523], morbidities [n = 1542]) controlling for community-average wealth, age, sex, household size, community size, and distance to markets. Wealthier people largely had better outcomes while inequality associated with more respiratory disease, a leading cause of mortality. Greater inequality and lower wealth were associated with higher blood pressure. Psychosocial factors did not mediate wealth-health associations. Thus, relative socio-economic position and inequality may affect health across diverse societies, though this is likely exacerbated in high-income countries.

Poverty is bad for health. People living in poverty are more likely to struggle to afford nutritious food, lack access to health care, or be overworked or stressed. This may make them susceptible to chronic diseases, contribute to faster aging, and shorten their lifespans. In high-income countries, there is growing evidence to suggest that a person’s ‘rank’ in society also impacts their health. For example, individuals who have a lower position in the social hierarchy report worse health outcomes, regardless of their incomes. But it is unclear why living in an unequal society or having a lower social status contributes to poorer health.

One possibility is that inequalities in society are creating a stressful environment that leads to worse physical and mental outcomes. It is thought that this stress largely comes from how humans evolved to prioritize reaching a higher social status over having a long and healthy life. If this is the case, this would mean that the link between social status and health would also be present in non-industrialized communities where social hierarchies tend to be less pronounced.

To test this, Jaeggi, Blackwell et al. studied the Indigenous Tsimane population in Bolivia who live in small communities and forage and farm their own food. The income and relative wealth of 870 households from 40 Tsimane communities were compared against various outcomes, including symptoms associated with depression, stress hormone levels, blood pressure, self-rated health and several diseases.

Jaeggi, Blackwell et al. found poverty and inequality did not negatively impact all of the health outcomes measured as has been previously reported for industrialized societies. However, blood pressure was higher among people with lower incomes or those who lived in more unequal communities. But because the Tsimane people generally have low blood pressure, the differences were too small to have much effect on their health. People who lived in more unequal communities were also three times more likely to have respiratory infections, but the reason for this was unclear.

This shows that social determinants such as a person’s wealth or inequality can affect health, even in communities with less rigid social hierarchies. In industrial societies the effect may be worse in part because they are compounded by lifestyle factors, such as diets rich in fat and sugar, and physical inactivity which can also increase blood pressure. This information may help policy makers reduce health disparities by addressing some of the social determinants of health and the lifestyle factors that cause them.

Investigating into the critical factors supporting healthy independent longevity: A proposition of a conceptual model with measurements during and beyond COVID-19 pandemic

This study investigated the factors that support the elderly citizens' perceived healthy independent longevity during and beyond the COVID-19 pandemic. The Structural Equation Modeling was conducted with the 1607 dataset collected from Japan to validate a proposed model with six antecedent factors. It has been found that "Town vibrancy" and "Mobility and transportations" have the most significant impact, whereas "Health and welfare policies" and "Community bonding" have a relatively lower impact on their perceived healthy longevity. The study has provided a conceptual model with measurements for further discussions in the field of study.