Increased mortality exposure within the family rather than individual mortality experiences triggers faster life-history strategies in historic human populations

Early Life Stress, Coping, and Cardiovascular Reactivity to Acute Social Stress

OBJECTIVE

Early life stress (ELS) occurring during childhood and adolescence is an established risk factor for later cardiovascular disease and dysregulated reactivity to acute social stress. This study examined whether ELS associations with baseline cardiovascular functioning, cardiovascular stress reactivity and recovery, and emotional stress reactivity vary across levels of emotion-oriented, task-oriented, and avoidant coping styles.

METHODS

The sample included 1027 adolescents and young adults (mean age = 19.29 years; 50% female; 64% Black, 34% non-Hispanic White) who reported on their ELS exposure and coping styles. Participants completed a standardized acute social stress test (the Trier Social Stress Test [TSST]), with heart rate (HR) and blood pressure (BP) measured before, during, and after the TSST. Self-reports of negative emotions during the TSST indexed emotional stress reactivity.

RESULTS

Multiple regression models adjusting for demographic factors and body mass index showed that ELS was associated with lower HR stress reactivity, avoidant coping was related to lower systolic BP and diastolic BP during stress and lower systolic BP during recovery, and higher emotion-oriented coping and lower task-oriented coping predicted greater emotional stress reactivity. A consistent pattern emerged where emotion-oriented coping amplified the associations between ELS and maladaptive stress responses (blunted cardiovascular stress reactivity and recovery; enhanced emotional stress reactivity), whereas lower levels of emotion-oriented coping were associated with resilient profiles among those who experienced ELS (lower resting HR, lower emotional stress reactivity, average HR and BP stress reactivity and recovery). However, low levels of emotion-oriented coping also conferred a risk of higher BP during recovery for those with high levels of ELS.

CONCLUSIONS

These results suggest that low to moderate levels of emotion-oriented coping promote optimal cardiovascular and emotional reactivity to acute stress among individuals exposed to ELS.

Famine-related mortality in early life and accelerated life histories in nineteenth-century Belgium

Density-dependent and extrinsic mortality are predicted to accelerate reproductive maturation. The first 5 years of life is a proposed sensitive period for life-history regulation. This study examines the ways in which local mortality during this sensitive period was related to subsequent marriage timing in nineteenth-century Belgium (n women = 11 892; n men = 14 140). Local mortality during the sensitive period was inversely associated with age at first marriage for men and women controlling for literacy, occupational status, population growth and migration. Cox regression indicated decreased time to marriage for women (HR = 1.661, 95% CI: 1.542-1.789) and men (HR = 1.327, 95% CI: 1.238-1.422) from high mortality municipalities. Rising population growth rates were associated with earlier marriage for men and women. Migration in general was associated with later marriage for men and women. Consistent with life-history predictions, harsh ecological conditions during early life such as famine coincided with earlier marriage.

No evidence for a relationship between MHC heterozygosity and life history strategy in a sample of North American undergraduates

Although allelic diversity at the major histocompatibility complex (MHC) has implications for adaptive immunity, mate choice, and social signalling, how diversity at the MHC influences the calibration of life history strategies remains largely uninvestigated. The current study investigated whether greater MHC heterozygosity was associated with markers of slower life history strategies in a sample of 789 North American undergraduates. Contrary to preregistered predictions and to previously published findings, MHC heterozygosity was not related to any of the psychological life history-relevant variables measured (including short- vs. long-term sexual strategy, temporal discounting, the Arizona life history battery, past and current health, disgust sensitivity, and Big Five personality traits). Further, no meaningful effects emerged when analysing women and men separately. Possible reasons for why the current results are inconsistent with previous work are discussed.

Effects of Individual Mortality Experience on Out-of-Wedlock Fertility in Eighteenth- and Nineteenth-Century Krummhörn, Germany

Life history theory predicts that exposure to high mortality in early childhood leads to faster and riskier reproductive strategies. Individuals who grew up in a high mortality regime will not overly wait until they find a suitable partner and form a stable union because premature death would prevent them from reproducing. Cox proportional hazard models were used to determine whether women who experienced sibling death during early childhood (0–5 years) reproduced earlier and were at an increased risk of giving birth to an illegitimate child, with illegitimacy serving as a proxy for risky sexual behavior. Furthermore, we investigate whether giving birth out of wedlock is influenced by individual mortality experience or by more promiscuous sexual behavior that is clustered in certain families. Models are fitted on pedigree data from the eighteenth- and nineteenth-century Krummhörn population in Germany. The results show a relationship between sibling death in early childhood and the risk of reproducing out of wedlock, and reproductive timing. The risk of giving birth out of wedlock is linked to individual mortality experience rather than to family-level effects. In contrast, adjustments in connubial reproductive timing are influenced more by family-level effects than by individual mortality experience.

Religion and fertility patterns: comparison of life history traits in Catholics and Protestants, Hallstatt (Austria) 1733-1908

Catholicism and Protestantism have different ways of promoting the family unit that could influence survival and fertility at a population level. Parish records in the Austrian village of Hallstatt allowed the reconstruction of Catholic and Protestant genealogies over a period of 175 years (1733-1908) to evaluate how religion and social changes affected reproduction and survival. Life history traits such as lifespan beyond 15 years, number of offspring, reproductive span, children born out of wedlock and child mortality were estimated in 5678 Catholic and 3282 Protestant individuals. The interaction of sex, time and religion was checked through non-parametric factorial ANOVAs. Religion and time showed statistically significant interactions with lifespan >15 years, number of offspring and age at birth of first child. Protestants lived longer, had a larger reproductive span and an earlier age at birth of first child. Before the famine crisis of 1845-1850, Protestants showed lower values of childhood mortality than Catholics. Comparison of the number of children born out of wedlock revealed small differences between the two religions. Religion influenced reproduction and survival, as significant differences were found between Catholics and Protestants. This influence could be explained in part by differential socioeconomic characteristics, since Protestants may have enjoyed better living and sanitary conditions in Hallstatt.

Financial opportunity costs and deaths among close kin are independently associated with reproductive timing in a contemporary high-income society

Evolutionary demography predicts that variation in reproductive timing stems from socio-ecologically contingent trade-offs between current and future reproduction. In contemporary high-income societies, the costs and benefits of current reproduction are likely to vary by socioeconomic status (SES). Two influential hypotheses, focusing on the parenthood 'wage penalty', and responses to local mortality have separately been proposed to influence the timing of parenthood. Economic costs of reproduction (i.e. income loss) are hypothesized to delay fertility, especially among high childhood SES individuals who experience greater opportunities to build capital through advantageous education and career opportunities. On the other hand, relatively low childhood SES individuals experience higher mortality risk, which may favour earlier reproduction. Here, we examine both hypotheses with a representative register-based, multigenerational dataset from contemporary Finland (N = 47 678). Consistent with each hypothesis, the predicted financial cost of early parenthood was smaller, and mortality among close kin was higher for individuals with lower childhood SES. Within the same dataset, lower predicted adulthood income and more kin deaths were also independently associated with earlier parenthood. Our results provide a robust demonstration of how economic costs and mortality relate to reproductive timing. We discuss the implications of our findings for demographic theory and public policy.

The Long Harm of Childhood: Childhood Exposure to Mortality and Subsequent Risk of Adult Mortality in Utah and The Netherlands

How do early-life conditions affect adult mortality? Research has yielded mixed evidence about the influence of infant and child mortality in birth cohorts on adult health and mortality. Studies rarely consider the specific role of mortality within the family. We estimated how individuals' exposure to mortality as a child is related to their adult mortality risk between ages 18 and 85 in two historical populations, Utah (USA) 1874-2015 and Zeeland (The Netherlands) 1812-1957. We examined these associations for early community-level exposure to infant and early (before sixth birthday) and late (before eighteenth birthday) childhood mortality as well as exposure during these ages to sibling deaths. We find that that exposure in childhood to community mortality and sibling deaths increases adult mortality rates. Effects of sibling mortality on adult all-cause mortality risk were stronger in Utah, where sibling deaths were less common in relation to Zeeland. Exposure to sibling death due to infection was related to the surviving siblings' risk of adult mortality due to cardiovascular disease (relative risk: 1.06) and metabolic disease (relative risk: 1.42), primarily diabetes mellitus, a result consistent with an inflammatory immune response mechanism. We conclude that early-life conditions and exposure to mortality in early life, especially within families of origin, contribute to adult mortality.

Child response processes as mediators of the association between caregiver intimate relationship instability and children's externalizing symptoms

Guided primarily by life history theory, this study was designed to identify how and why early exposure to caregiver intimate relationship instability uniquely predicts children's externalizing symptoms in the context of other dimensions of unpredictability characterized by residential and parental job transitions. Participants included 243 preschool children (Mage = 4.60 years) and their mothers who participated in 3 annual measurement occasions (i.e., preschool, kindergarten, first grade). Supporting the first link in the hypothesized mediational chain, the results of structural equation modeling analyses indicated that caregiver intimate relationship instability uniquely predicted a pattern of response processes over a 1-year period characterized by negative family representations, dominant interpersonal strategies for regulating resources, and diminished task persistence. Latent difference score analyses of each of these response processes over the 1-year period, in turn, uniquely predicted a multiinformant (i.e., mother, teacher, experimenter) assessment of children's externalizing symptoms over a 2-year period. Mediational findings were robust after accounting for the negligible roles of residential and occupational changes as simultaneous predictors. Results are interpreted in the context of how they inform and support life history theory as well as other conceptual (e.g., attachment and emotional security theory) models. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Early-life mortality clustering in families: A literature review

Research on early-life mortality in contemporary and historical populations has shown that infant and child mortality tend to cluster in a limited number of high-mortality families, a phenomenon known as 'mortality clustering'. This paper is the first to review the literature on the role of the family in early-life mortality. Contemporary results, methodological and theoretical shortfalls, recent developments, and opportunities for future research are all discussed in this review. Four methodological approaches are distinguished: those based on sibling deaths, mother heterogeneity, thresholds, and excess deaths in populations. It has become clear from research to date that the death of an older child harms the survival chances of younger children in that family, and that fertility behaviour, earlier stillbirths, remarriages, and socio-economic status all explain mortality clustering to some extent.

The behavioural constellation of deprivation: Causes and consequences

Socioeconomic differences in behaviour are pervasive and well documented, but their causes are not yet well understood. Here, we make the case that a cluster of behaviours is associated with lower socioeconomic status (SES), which we call “the behavioural constellation of deprivation.” We propose that the relatively limited control associated with lower SES curtails the extent to which people can expect to realise deferred rewards, leading to more present-oriented behaviour in a range of domains. We illustrate this idea using the specific factor of extrinsic mortality risk, an important factor in evolutionary theoretical models. We emphasise the idea that the present-oriented behaviours of the constellation are a contextually appropriate response to structural and ecological factors rather than a pathology or a failure of willpower. We highlight some principles from evolutionary theoretical models that can deepen our understanding of how socioeconomic inequalities can become amplified and embedded. These principles are that (1) small initial disparities can lead to larger eventual inequalities, (2) feedback loops can embed early-life circumstances, (3) constraints can breed further constraints, and (4) feedback loops can operate over generations. We discuss some of the mechanisms by which SES may influence behaviour. We then review how the contextually appropriate response perspective that we have outlined fits with other findings about control and temporal discounting. Finally, we discuss the implications of this interpretation for research and policy.

Early-life disease exposure and associations with adult survival, cause of death, and reproductive success in preindustrial humans

A leading hypothesis proposes that increased human life span since 1850 has resulted from decreased exposure to childhood infections, which has reduced chronic inflammation and later-life mortality rates, particularly from cardiovascular disease, stroke, and cancer. Early-life cohort mortality rate often predicts later-life survival in humans, but such associations could arise from factors other than disease exposure. Additionally, the impact of early-life disease exposure on reproduction remains unknown, and thus previous work ignores a major component of fitness through which selection acts upon life-history strategy. We collected data from seven 18th- and 19th-century Finnish populations experiencing naturally varying mortality and fertility levels. We quantified early-life disease exposure as the detrended child mortality rate from infectious diseases during an individual's first 5 y, controlling for important social factors. We found no support for an association between early-life disease exposure and all-cause mortality risk after age 15 or 50. We also found no link between early-life disease exposure and probability of death specifically from cardiovascular disease, stroke, or cancer. Independent of survival, there was no evidence to support associations between early-life disease exposure and any of several aspects of reproductive performance, including lifetime reproductive success and age at first birth, in either males or females. Our results do not support the prevailing assertion that exposure to infectious diseases in early life has long-lasting associations with later-life all-cause mortality risk or mortality putatively linked to chronic inflammation. Variation in adulthood conditions could therefore be the most likely source of recent increases in adult life span.

Trade-offs between acquired and innate immune defenses in humans

Immune defenses provide resistance against infectious disease that is critical to survival. But immune defenses are costly, and limited resources allocated to immunity are not available for other physiological or developmental processes. We propose a framework for explaining variation in patterns of investment in two important subsystems of anti-pathogen defense: innate (non-specific) and acquired (specific) immunity. The developmental costs of acquired immunity are high, but the costs of maintenance and activation are relatively low. Innate immunity imposes lower upfront developmental costs, but higher operating costs. Innate defenses are mobilized quickly and are effective against novel pathogens. Acquired responses are less effective against novel exposures, but more effective against secondary exposures due to immunological memory. Based on their distinct profiles of costs and effectiveness, we propose that the balance of investment in innate versus acquired immunity is variable, and that this balance is optimized in response to local ecological conditions early in development. Nutritional abundance, high pathogen exposure and low signals of extrinsic mortality risk during sensitive periods of immune development should all favor relatively higher levels of investment in acquired immunity. Undernutrition, low pathogen exposure, and high mortality risk should favor innate immune defenses. The hypothesis provides a framework for organizing prior empirical research on the impact of developmental environments on innate and acquired immunity, and suggests promising directions for future research in human ecological immunology.