Kai P. Willführ

Are Stepparents Always Evil? Parental Death, Remarriage, and Child Survival in Demographically Saturated Krummhörn (1720–1859) and Expanding Québec (1670–1750)

Parental death precipitates a cascade of events leading to more or less detrimental exposures, from the sudden and dramatic interruption of parental care to cohabitation with stepparents and siblings in a recomposed family. This article compares the effect of early parental loss on child survival in the past in the Krummhörn region of East Frisia (Germany) and among the French Canadian settlers of the Saint Lawrence Valley (Québec, Canada). The Krummhörn region was characterized by a saturated habitat, while the opportunities for establishing a new family were virtually unlimited for the French Canadian settlers. Early parental loss had quite different consequences in these dissimilar environments. Event history analyses with time-varying specification of family structure are used on a sample of 7,077 boys and 6,906 girls born between 1720 and 1859 in the Krummhörn region and 31,490 boys and 33,109 girls whose parents married between 1670 and 1750 in Québec. Results indicate that in both populations, parental loss is associated with increased infant and child mortality. Maternal loss has a universal and consistent effect for both sexes, while the impact of paternal loss is less easy to establish and interpret. On the other hand, the effect of the remarriage of the surviving spouse is population-specific: the mothers remarriage has no effect in Krummhörn, while it is beneficial in Québec. In contrast, the fathers remarriage in Krummhörn dramatically reduces the survival chances of the children born from his former marriage, while such an effect is not seen for Québec. These population-specific effects appear to be driven by the availability of resources and call into question the universality of the “Cinderella” effect.

Are Stepmothers Evil or Simply Unskilled? Infant Death Clustering in Recomposed Families

We measure the concentration of infant deaths in families in the historical populations of Krummhörn, Germany and Québec, Canada in order to investigate whether mothers in recomposed families differ regarding their maternal quality. In particular, we are interested in whether stepmothers in Krummhörn are responsible for a diminution in the survival of their stepchildren because they poorly substitute maternal child care or because they disadvantage their stepchildren. The concentrations of infant deaths within the two populations are measured with Lorenz curves and Gini coefficients, and are compared with expected concentrations given by draws from a binomial distribution. Alleged differences between actual and calculated concentrations represent “causal” death clustering. In the Krummhörn region there is little evidence for “causal” death clustering that would indicate variations regarding their maternal quality, whereas Québec mothers exhibit a distinctively higher concentration of infant deaths.

The consequences of sibling rivalry on survival and reproductive success across different ecological contexts: a comparison of the historical Krummhörn and Quebec populations

Abstract This article investigates the relationship between additional siblings and the probability of offspring survival, marriage, and fertility across the historical populations of the St Lawrence Valley in Quebec (1670–1799) and the Krummhörn region in Germany (1720–1874). Both populations existed in agriculturally based economies, but differ in important ways. The Krummhörn population faced a fixed supply of land, which was concentrated amongst a small number of farmers. Most individuals were landless agricultural workers who formed a relatively competitive labor supply for the large farmers. In contrast, individuals in Quebec had access to a large supply of land, but with far fewer available agricultural workers, and had to rely on their family to develop and farm that land. Results indicate that more siblings of the same gender were generally associated with increases in mortality during infancy and childhood, later ages of first marriage, and fewer numbers of children ever born. For mortality and age at first marriage, the effects of sibling formation appear strongest in the Krummhörn region. Notwithstanding these observed differences, the general consistency and robustness of the sibship effect across the different ecological and economic contexts is our most interesting result. In addition, through side-by-side comparison of across-family and within-family analyses, we argue that sibling competition – or sacrifice – is manifested as an internal familial dynamic, but is obscured in non-fixed effects models by a broader trend of family cooperation. Through this comparison we are able to reconcile family solidarity and sibling competition/sacrifice as coexisting phenomena. Results are robust to inclusion of covariate interactions with time, inclusion of indicators for high levels of extrinsic risk, estimation of shared frailty models, alternative methods of dealing with ties in the dataset, including recomposed families in the dataset, excluding individuals whose death dates are ‘heaped’, and excluding individuals born to large families.

Essential Building Blocks of Human Nature

Our Origins: How and Why We Do and Do Not Differ from Primates Peter Kappeler.- Our Children: Parental Decisions - How Much to Invest in Your Offspring Mary K. Shenk.- Our Social Roots: How Local Ecology Shapes our Social Structures Ruth Mace.- Our Selections and Decisions: Inherent Features of the Nervous System? Frank Rosler.- Our Gods: Variation in Supernatural Minds Benjamin G. Purzycki and Richard Sosis.- Our Preferences: Why We Like What We Like Karl Grammer and Elisabeth Oberzaucher.- Our Appetite for Information: Invented Environment, Non-Transparent Mind, and Evolved Preferences Matthias Uhl.- Our Best Shot at Truth: Why Humans Evolved Mathematical Abilities Niklas Krebs.- Our Way to Understand the World: Darwins Controversial Inheritance Michael Schmidt-Salomon.- Index.

Disease load at conception predicts survival in later epidemics in a historical French-Canadian cohort, suggesting functional trans-generational effects in humans

Objective Functional trans-generational and parental effects are potentially important determinants of health in several mammals. For humans, the existing evidence is weak. We investigate whether disease exposure triggers functional trans-generational response effects among humans by analyzing siblings who were conceived under different disease loads, and comparing their mortality in later epidemics. Under functional trans-generational response mechanisms, we expect that those who were conceived under high pathogenic stress load will have relatively low mortality during a later epidemic. Methods We use data from the Registre de la Population du Québec Ancien, which covers the historical population living in St. Lawrence Valley, Québec, Canada. Children born in 1705–1724 were grouped according to their exposure during conception to the measles 1714–15 epidemic. The 1714–15 epidemic was followed by two mortality crises in 1729–1734. The cause of the first crises in 1729 is not exactly known. The second crisis in 1732 was caused by a smallpox epidemic. Using proportional hazard Cox regression models with multivariate adjustment and with fixed-effects approach that compare siblings, we analyze whether mortality in 1729–1734 is affected by exposure to the 1714–15 epidemic. Results Children who were conceived during the peak of the measles epidemic of 1714–15 exhibited significantly lower mortality during the 1729–1734 crisis than those who were born before the 1714–15 epidemic (mortality hazard ratio 0.106, p<.05 in multivariate adjusted models; 0.142 p<.1 in sibling comparison models). Conclusions The results are consistent with a trans-generational mechanism that functionally responds to pathogen stress and suggest that early disease exposure may be protective later in life. Alternative explanations for the mortality patterns are discussed and shown to be problematic.

Phenotype-environment mismatch due to epigenetic inheritance? Programming the offspring’s epigenome and the consequences of migration

It has been suggested that epigenetic inheritance is an important factor influencing mortality. We use data about the historical population of Québec (years 1670–1740) to study whether parents modify their offsprings phenotype epigenetically prior to conception in response to predicted/perceived mortality. If so, children growing up in the predicted environment enjoy a phenotype‐environment‐match that should lower mortality, whereas children growing up in a nonpredicted environment should have a higher mortality.

When the mother-in-law is just as good—Differential mortality of reproductive females by family network composition

Motivated by the cooperative breeding hypothesis, we investigate the effect of having kin on the mortality of reproductive women based on family reconstitutions for the Krummhörn region (East Frisia, Germany, 1720–1874). We rely on a combination of Cox clustered hazard models and hazard models stratified at the family level. In order to study behavior-related effects, we run a series of models in which only kin who lived in the same parish are considered. To investigate structural, non-behavior-related effects, we run a different model series that include all living kin, regardless their spatial proximity. We find that women of reproductive age who had a living mother had a reduced mortality risk. It appears that having living sisters had an ambivalent impact on women’s mortality: i.e., depending on the socioeconomic status of the family, the effect of having living sisters ranged between representing a source of competition and representing a source of support. Models which are clustered at the family level suggest that the presence of a living mother-in-law was associated with reduced mortality among her daughters-in-law especially among larger-scale farm families. We interpret this finding as a consequence of augmented consanguineous marriages among individuals of higher social strata. For instance, in first cousin marriages, the mother-in-law could also be a biological aunt. Thus, it appears that among the wealthy elite, the genetic in-law conflict was neutralized to some extent by family solidarity. This result further suggests that the tipping point of the female trade-off between staying with the natal family and leaving the natal family to join an economically well-established in-law family might have been reached very quickly among women living under the socioeconomic conditions of the Krummhörn region.

Mortality Crises and Their Consequences for Human Life Histories

Studies on the long-term consequences of crises experienced in early childhood do not draw a uniform picture as to the extent that such crises have an impact on later life. There are studies showing that those who survive a crisis exhibit higher mortality in later life but also that these individuals exhibit lower or unchanged mortality. In this chapter, we develop a hypothesis according to which the impact on later life (or on survival) is caused by the severity of the crisis and that—independent of the nature of the crisis—these effects might be mediated by the immune system.