Hand Asymmetry Does Not Relate to Key Life History Traits in Post-Menopausal Contemporary Finnish Women

Associations between fluctuating asymmetry (FA, a putative marker of developmental instability, DI) and life history traits have received a great deal of attention in the non-human literature. However, the patterns found are very heterogeneous and generalizations are difficult to make. In humans, only a few studies have related FA to life histories and fitness. In this paper we study such relationships using hand FA and several key life history traits in 209 post-menopausal Finnish women born between 1946 and 1958. Asymmetry measurements were based on scans of the hands and the life histories of these women were collected using questionnaires. No significant associations were detected and trends were opposite to expectations. We did find evidence for directional asymmetry, as traits in the right hand were larger on average. This may be due to handedness, questioning the usefulness of hand FA as a measure of DI. We conclude that future studies in humans should carefully examine the usefulness of traits as measures of DI

Natural Selection on Female Life-History Traits in Relation to Socio-Economic Class in Pre-Industrial Human Populations

Life-history theory predicts that resource scarcity constrains individual optimal reproductive strategies and shapes the evolution of life-history traits. In species where the inherited structure of social class may lead to consistent resource differences among family lines, between-class variation in resource availability should select for divergence in optimal reproductive strategies. Evaluating this prediction requires information on the phenotypic selection and quantitative genetics of life-history trait variation in relation to individual lifetime access to resources. Here, we show using path analysis how resource availability, measured as the wealth class of the family, affected the opportunity and intensity of phenotypic selection on the key life-history traits of women living in pre-industrial Finland during the 1800s and 1900s. We found the highest opportunity for total selection and the strongest selection on earlier age at first reproduction in women of the poorest wealth class, whereas selection favoured older age at reproductive cessation in mothers of the wealthier classes. We also found clear differences in female life-history traits across wealth classes: the poorest women had the lowest age-specific survival throughout their lives, they started reproduction later, delivered fewer offspring during their lifetime, ceased reproduction younger, had poorer offspring survival to adulthood and, hence, had lower fitness compared to the wealthier women. Our results show that the amount of wealth affected the selection pressure on female life-history in a pre-industrial human population

Height, Age at First Birth, and Lifetime Reproductive Success: A Prospective Cohort Study of Finnish Male and Female Twins

Peer reviewe

Allocating Logging Rights in Peruvian Amazonia—Does It Matter to Be Local?

Peer reviewe

Increased ROS Production: A Component of the Longevity Equation in the Male Mygalomorph, Brachypelma albopilosa

The diversity of longevities encountered in wildlife is one of the most intriguing problems in biology. Evolutionary biologists have proposed different theories to explain how longevity variability may be driven by bad genes expression in late life or by gene pleiotropic effects. This reflexion has stimulated, in the last ten years, an active research on the proximal mechanisms that can shape lifespan. Reactive oxygen species (ROS), i.e., the by-products of oxidative metabolism, have emerged as the main proximate cause of ageing. Because ROS are mainly produced by the mitochondria, their production is linked to metabolic rate, and this may explain the differences in longevity between large and small species. However, their implication in the sex difference in longevity within a species has never been tested, despite the fact that these differences are widespread in the animal kingdom.Mitochondrial superoxide production of hemolymph immune cells and antioxidant and oxidative damages plasma levels were measured in adult male and female B. albopilosa at different ages. We found that female spiders are producing less mitochondrial superoxide, are better protected against oxidative attack and are then suffering less oxidative damages than males at adulthood.In tarantulas, once reaching sexual maturity, males have a life expectancy reduced to 1 to 2 years, while females can still live for 20 years, in spite of the fact that females continue to grow and moult. This study evidences an increased exposure of males to oxidative stress due to an increase in mitochondrial superoxide production and a decrease in hemolymph antioxidant defences. Such a phenomenon is likely to be part of the explanation for the sharp reduction of longevity accompanying male tarantula maturity. This opens several fundamental research roads in the future to better understand how reproduction and longevity are linked in an original ageing model

Dead or alive: The interplay of grandparental investment according to the survival status of other grandparent types

BACKGROUND According to the kin selection theory, grandparental investment has its evolutionary roots in the individuals’ aim to maximise their inclusive fitness. Owing to an increasing overlap between successive generations in modern affluent populations, the importance of grandparental investment remains high. Despite the growing literature on this topic, there is limited knowledge regarding how the survival status of different grandparent types influences each other’s investment in grandchildren.  OBJECTIVE The present study examined how the survival status of grandparents influenced grandparental investment among other grandparent types using a wide range of grandparental investment variables divided into two latent constructs measuring relationship quality between grandparents and grandchildren and grandparental involvement in grandchildren. METHODS We used Bayesian structural equation modeling with multiple-indicator latent variables and the Involved Grandparenting and Child Well-Being Survey, providing nationally representative data of British and Welsh adolescents aged 11–16-years. RESULTS Maternal grandmothers’ investment was most strongly influenced by whether other grandparents were dead or alive. Living maternal grandfathers and paternal grandmothers had an almost identical positive influence on the investment of maternal grandmothers in their grandchildren. Weaker evidence suggested that living maternal grandmothers decreased the investment of paternal grandmothers and grandfathers. CONCLUSIONS These findings suggest the opposite influences of the survival status of paternal and maternal grandmothers on their investment. The results are discussed with reference to kin competition and incidental exposure. CONTRIBUTION The current study represents the first attempt to test whether the survival status of other grandparents is associated with focal grandparents’ investment within and between lineages</p

Atmospheric humidity affects global variation of bat echolocation via indirect effects

The peak frequency of bat echolocation is a species-specific functional trait linked to foraging ecology. It is tailored via evolution to suit conditions within the distribution range of each species, but the evolutionary drivers are not yet well-understood. Global patterns of humidity correlate with many aspects of bat ecology. We hypothesized that atmospheric absolute humidity could explain global peak frequency variation directly and indirectly via increasing species body size and bat species richness. These hypotheses were tested using Bayesian phylogenetic path analysis on 226 tropical and subtropical bat species. In line with our predictions, we found a positive total effect of humidity on peak frequency, which was dominated by the positive indirect effects via body size and bat species richness. We did not observe the negative direct effect of humidity on peak frequency, which was hypothesized based on atmospheric attenuation of sound. In line with our expectations, excluding the predominantly clutter foraging bat families from our dataset downplayed the importance of the richness-mediated route. To conclude, our findings suggest that indirect effects, owing to ecology and biogeography of bat taxa, play a major role in the global relationship between peak frequency and atmospheric humidity.Peer reviewe

Males have more aggressive and less sociable personalities than females in semi-captive Asian elephants

Personality, i.e. consistent between-individual differences in behaviour, has been documented in many species. Yet little is known about how males and females of long-lived, highly social species differ in their measures of personality structure. We investigated sex differences in the mean, variance, and covariance of three previously reported personality traits (Attentiveness, Sociability, Aggressiveness) in 150 female and 107 male Asian elephants (Elephas maximus) from a semi-captive population in Myanmar. These three personality traits were obtained by performing exploratory factor analysis on 28 behavioural items that had been rated by experienced elephant handlers. We found that males scored significantly higher on Aggressiveness and tended to score lower on Sociability than females. However, no sex difference was found in the mean scores of Attentiveness. Variances for the three personality traits did not differ between the sexes, suggesting that male and female elephants share the same range of personality variation. Likewise, trait covariances were similar between the sexes. While both sexes show complex sociality in the wild, female Asian elephants typically live in highly social family units, whereas male elephants' social bonds are weaker. Males usually form dominance ranks by aggressive interactions, especially during musth. Our results on a large sample of individuals living in their natural environment are thus in agreement with elephant life-histories and parallel the findings of sex differences in other long-lived highly social species with similar life-histories

Kin recognition and step-paternal investment: the effect of childhood co-residence duration

Evolutionarily relevant nepotistic kin investment requires reliable kin detection. Evolutionary scholars have argued that childhood co-residence is one of the most important indirect cues for kinship. While childhood co-residence duration has been found to correlate with kin investment in intragenerational studies (i.e., among siblings), intergenerational investigations considering the association between childhood co-residence duration and kin investment have been scarce. Here, we investigate whether the investment of biological and stepfathers is correlated with childhood co-residence duration. We used data from adolescents and adults (aged 17–19, 27–29, and 37–39 years) from the German Panel Analysis of Intimate Relationships and Family Dynamics (Pairfam), wave 2, collected in 2010–2011. Paternal investment was measured as financial and practical help, emotional support, intimacy, and emotional closeness. We found that while stepfathers invested less than biological fathers, both biological and stepfathers’ investments increased with increased childhood co-residence duration in most measures. Financial help correlated with childhood co-residence in stepfathers but not in biological fathers who helped financially more than stepfathers regardless of childhood co-residence duration. Emotional support, intimacy, and emotional closeness were correlated with childhood co-residence in both biological fathers and stepfathers. Practical help did not correlate with co-residence in either father. Thus, our results partially support the hypothesis that childhood co-residence duration serves as a kin detection cue and directs intergenerational altruism.</p

The interplay of grandparental investment according to the survival status of other grandparent types

Inclusive fitness theory predicts that grandparental investment in grandchildren aims to maximise their inclusive fitness. Owing to an increasing overlap between successive generations in modern affluent populations, the importance of grandparental investment remains high. Despite the growing literature, there is limited knowledge regarding how the survival status of different grandparent types influences each other's investment in grandchildren. This question was studied by using the Involved Grandparenting and Child Well-Being Survey, which provided nationally representative data of English and Welsh adolescents aged 11-16-years. We applied Bayesian structural equation modeling (BSEM) where grandparental investment in grandchildren was modelled using multi-indicator unobserved latent variable. Our results showed that maternal grandmothers' investment was increased by having a living maternal grandfather but not vice versa. Having a living maternal grandmother was also associated with decreased investment of paternal grandparents while the opposite was not found. These findings indicate that the association between the survival status of other grandparents and the focal grandparents' investment varies between grandparent types