Early-life environment and differences in costs of reproduction in a preindustrial human population

Evolution of infant mortality and family-based risk factors in a preindustrial Austrian population: 1630-1908

Infant mortality, a reflection of socioeconomic and health conditions of a population, is shaped by diverse factors. This study delves into a pre-industrial population, scrutinizing neonatal and post-neonatal deaths separately. Family factors such as mortality crises, religion, and legitimacy are also explored. Data of 9,086 people obtained through multigenerational information from ecclesiastic records from 1603 to 1908 were analysed by means of a joinpoint regression analysis. Death risk was assessed with univariate and multivariate Cox Proportional Hazard models. Early neonatal mortality was 5.6% of births and showed a gradual and steady increase from 1630 to 1908, with no substantial improvement over the three centuries analysed. Late neonatal (4.3% of births) and post-neonatal mortality (18.7% of births) shared a different pattern, showing a decline between the mid-18th and mid-19th centuries, and an increase by the 20th century that could be caused by socioeconomic factors and the impact of several epidemics. In the historical population of Hallstatt, infant survival was influenced by the sex of the newborn, the death of the mother and the precedent sibling, and by the birth interval. Environmental and cultural factors, such as mortality crises and religion, influenced late neonatal and post-neonatal mortality, but not early neonatal mortality. The results highlight the need to independently assess early neonatal mortality in studies of infant mortality in historical populations, and to use as complete time periods as possible to capture differences in mortality patterns.

Running, walking, and cross-country skiing: how to shape adolescents' personalities through physical activity?

Adolescence is crucial for personality development, and sports play a significant role. This study investigates the impact of various sports on the personality traits of junior high and high school students in Shandong Province, focusing on neuroticism, extraversion, openness, agreeableness, and conscientiousness. Utilizing data from the "Database of Youth Health," we employed Seemingly Unrelated Regression (SUR) and Generalized Structural Equation Modeling (GSEM) to analyze the effects of physical activity on personality development. Findings reveal that walking significantly enhances openness and decreased neuroticism, while jogging/running substantially improves extraversion, agreeableness, and conscientiousness. Cross-country skiing, however, negatively impacts all assessed personality traits. In addition, the importance of gender differences in the relationship between physical activity and personality development was revealed. The results offer insights for promoting adolescent personality development through targeted sports activities.

Sons Shorten Mother's Lifespan in Preindustrial Families with a High Level of Infant Mortality

AbstractIn dimorphic vertebrates where males are larger than females, the energetic costs of producing and rearing sons can exceed those of daughters. In humans, differences in maternal energy intake suggest that sons require 10% and 7% more energy than daughters during pregnancy and lactation, respectively. Due to a trade-off between reproduction and somatic maintenance, having sons is expected to have a more pronounced detrimental impact on a mother's lifespan than having daughters. A limitation of previous studies investigating this hypothesis is that the increased mortality cost of having sons was assumed to affect all mothers equally. Using a dataset from a preindustrial Quebec population monitored over two centuries, we found that the number of sons decreased postmenopausal lifespan only in mothers experiencing high infant mortality. Our study highlights the importance of interindividual variation in environmental conditions and maternal health when studying effects of offspring sex on reproductive costs.

Stochasticity Explains Nongenetic Inheritance of Lifespan and Apparent Trade-Offs between Reproduction and Aging

Stochastic effects are central to the biology and demography of aging. Genetically identical individuals do not all die at the exact same time but show a distribution of lifespan. Although such effects are appreciated, any cascading effects from the stochastic effects of aging are underappreciated. We show here that genetically identical female flies (Drosophila melanogaster) that live long produce longer-lived daughters. In line with previous work, we also find that daughters born to older mothers are shorter-lived, also termed the Lansing effect. We further show that longer-lived flies produce less offspring, suggesting an apparent trade-off due to stochastic effects alone. We explain these effects using an extension of the reliability theory of aging by dichotomizing aging physiology in reproduction and lifespan-supporting units. These simple models reproduce the nongenetic inheritance of lifespan, the Lansing effect, and trade-offs between reproduction and lifespan. Our work implies that if nongenetic inheritance of lifespan is widespread, it explains the generally low heritability of this trait. Furthermore, trade-offs between performance, for example, reproduction, and lifespan may be less widespread than predicted by the evolutionary biology of aging, stemming from stochasticity rather than differential investment. Antiaging treatments could therefore come without any unintended costs to other physiology, a perceived risk that limits the translation of these treatments to humans.

Variations in immune parameters with age in a wild rodent population and links with survival

Recent findings suggest that immune functions do not unidirectionally deteriorate with age but that a potentially adaptive remodeling, where functions of the immune system get downregulated while others get upregulated with age could also occur. Scarce in wild populations, longitudinal studies are yet necessary to properly understand the patterns and consequences of age variations of the immune system in the wild. Meanwhile, it is challenging to understand if the observed variations in immune parameters with age are due to changes at the within-individual level or to selective (dis)appearance of individuals with peculiar immune phenotypes. Thanks to a long-term and longitudinal monitoring of a wild Alpine marmot population, we aimed to understand within- and between-individual variation in the immune phenotype with age, in order to improve our knowledge about the occurrence and the evolutionary consequences of such age variations in the wild. To do so, we recorded the age-specific leukocyte concentration and leukocyte profile in repeatedly sampled dominant individuals. We then tested whether the potential changes with age were attributable to within-individual variations and/or selective (dis)appearance. Finally, we investigated if the leukocyte concentration and profiles were correlated to the probability of death at a given age. The leukocyte concentration was stable with age, but the relative number of lymphocytes decreased, while the relative number of neutrophils increased, over the course of an individual's life. Moreover, between individuals of the same age, individuals with fewer lymphocytes but more neutrophils were more likely to die. Therefore, selective disappearance seems to play a role in the age variations of the immune parameters in this population. Further investigations linking age variations in immune phenotype to individual fitness are needed to understand whether remodeling of the immune system with age could or could not be adaptive.

The Effect of Manipulated Prenatal Conditions on Growth, Survival, and Reproduction Throughout the Complete Life Course of a Precocial Bird

The quality of the environment individuals experience during development is commonly regarded as very influential on performance in later life. However, studies that have experimentally manipulated the early-life environment and subsequently measured individual performance in all components of fitness over the complete life course are scarce. In this study, we incubated fertile eggs of Japanese quail (Coturnix japonica) at substandard and standard incubation temperature, and monitored growth, survival, and reproduction throughout the complete life course. While embryonic development was slower and hatching success tended to be lower under substandard incubation temperature, the prenatal treatment had no effect on post-hatching growth, survival to sexual maturity, or age at first reproduction. In adulthood, body mass and investment in individual egg mass peaked at middle age, irrespective of the prenatal treatment. Individual reproduction rate declined soon after its onset, and was higher in females that lived longer. Yet, reproduction, and its senescence, were independent of the prenatal treatment. Similarly, adult survival over the complete lifespan was not affected. Hence, we did not find evidence for effects on performance beyond the developmental period that was manipulated. Our results suggest that effects of unfavorable developmental conditions on individual performance later in life could be negligible in some circumstances.

Examining the trade-offs between human fertility and longevity over three centuries using crowdsourced genealogy data

The evolution theory of ageing predicts that reproduction comes with long-term costs of survival. However, empirical studies in human species report mixed findings of the relationship between fertility and longevity, which varies by populations, time periods, and individual characteristics. One explanation underscores that changes in survival conditions over historical periods can moderate the negative effect of human fertility on longevity. This study investigates the fertility-longevity relationship in Europe during a period of rapid modernisation (seventeenth to twentieth centuries) and emphasises the dynamics across generations. Using a crowdsourced genealogy dataset from the FamiLinx project, our sample consists of 81,924 women and 103,642 men born between 1601 and 1910 across 16 European countries. Results from multilevel analyses show that higher fertility has a significantly negative effect on longevity. For both women and men, the negative effects are stronger among the older cohorts and have reduced over time. Moreover, we find similar trends in the dynamic associations between fertility and longevity across four geographical regions in Europe. Findings and limitations of this study call for further investigations into the historical dynamics of multiple mechanisms behind the human evolution of ageing.

The 4 D's of Pellagra and Progress

Nicotinamide homeostasis is a candidate common denominator to explain smooth transitions, whether demographic, epidemiological or economic. This 'NAD world', dependent on hydrogen-based energy, is not widely recognised as it is neither measured nor viewed from a sufficiently multi-genomic or historical perspective. Reviewing the importance of meat and nicotinamide balances during our co-evolution, recent history suggests that populations only modernise and age well with low fertility on a suitably balanced diet. Imbalances on the low meat side lead to an excess of infectious disease, short lives and boom-bust demographics. On the high side, meat has led to an excess of degenerative, allergic and metabolic disease and low fertility. A 'Goldilocks' diet derived from mixed and sustainable farming (preserving the topsoil) allows for high intellectual capital, height and good health with controlled population growth resulting in economic growth and prosperity. Implementing meat equity worldwide could lead to progress for future generations on 'spaceship' earth by establishing control over population quality, thermostat and biodiversity, if it is not already too late.

Nicotinamide and Demographic and Disease transitions: Moderation is Best

Good health and rapid progress depend on an optimal dose of nicotinamide. Too little meat triggers the neurodegenerative condition pellagra and tolerance of symbionts such as tuberculosis (TB), risking dysbioses and impaired resistance to acute infections. Nicotinamide deficiency is an overlooked diagnosis in poor cereal-dependant economies masquerading as 'environmental enteropathy' or physical and cognitive stunting. Too much meat (and supplements) may precipitate immune intolerance and autoimmune and allergic disease, with relative infertility and longevity, via the tryptophan-nicotinamide pathway. This switch favours a dearth of regulatory T (Treg) and an excess of T helper cells. High nicotinamide intake is implicated in cancer and Parkinson's disease. Pro-fertility genes, evolved to counteract high-nicotinamide-induced infertility, may now be risk factors for degenerative disease. Moderation of the dose of nicotinamide could prevent some common diseases and personalised doses at times of stress or, depending on genetic background or age, may treat some other conditions.