Grandparental presence is known to correlate with the number of grandchildren born, and this effect may vary according to grandparental sex and lineage. However, existing studies of grandparental effects on fertility mostly concern traditional subsistence societies, while evidence from contemporary developed societies is both scarce and mixed. Here, we explore how grandparents affect the transition to second and subsequent children in the contemporary United Kingdom. The longitudinal Millennium Cohort Study (n = 10,295 families) was used to study the association between (...) grandparental investment and parents’ probability of having a new child within 4.5 years. Results show that contact with paternal grandparents is associated with higher probability of parents having a second child. In contrast, contact with maternal grandparents is associated with lower probability of having a third or subsequent child. Kin may have opposite effects on fertility even in contemporary societies, which may explain the lack of consistent effects of grandparental investment on fertility in previous studies. (shrink)

We conducted a meta-analysis of 17 studies that tested for an association between grandparental survival and grandchild survival in patrilineal populations. Using two different methodologies, we found that the survival of the maternal grandmother and grandfather, but not the paternal grandmother and grandfather, was associated with decreased grandoffspring mortality. These results are consistent with the findings of psychological studies in developed countries (Coall and Hertwig Behavioral and Brain Sciences 33:1-59, 2010). When tested against the predictions of five hypotheses (confidence of (...) paternity; grandmothering, kin proximity, grandparental senescence, and local resource competition), our meta-analysis results are most in line with the local resource competition hypothesis. In patrilineal and predominantly patrilocal societies, the grandparents who are most likely to live with the grandchildren have a less beneficial association than those who do not. We consider the extent to which these results may be influenced by the methodological limitations of the source studies, including the use of retrospective designs and inadequate controls for confounding variables such as wealth. (shrink)

This paper examines the effects of three different types of father absence on the timing of life history events among women in rural Bangladesh. Age at marriage and age at first birth are compared across women who experienced different father presence/absence conditions as children. Survival analyses show that daughters of fathers who divorced their mothers or deserted their families have consistently younger ages at marriage and first birth than other women. In contrast, daughters whose fathers were labor migrants have consistently (...) older ages at marriage and first birth. Daughters whose fathers died when they were children show older ages at marriage and first birth than women with divorced/deserted fathers and women with fathers present. These effects may be mediated by high socioeconomic status and high levels of parental investment among the children of labor migrants, and a combination of low investment, high psychosocial stress, and low alloparental investment among women with divorced/deserted fathers. Our findings are most consistent with the Child Development Theory model of female life history strategies, though the Paternal Investment and Psychosocial Acceleration models also help explain differences between women in low paternal investment situations (e.g., father divorced/abandoned vs. father dead). Father absence in and of itself seems to have little effect on the life history strategies of Bangladeshi women once key reasons for or correlates of absence are controlled, and none of the models is a good predictor of why women with deceased fathers have delayed life histories compared with women whose fathers are present. (shrink)

Support from grandparents plays a role in mothers’ perinatal mental health. However, previous research on maternal mental health has mainly focused on influences of partner support or general social support and neglected the roles of grandparents. In this narrative review and meta-analysis, the scientific evidence on the association between grandparental support and maternal perinatal mental health is reviewed. Searches in PubMed, EMBASE, MEDLINE, Scopus, and PsycINFO yielded 11 empirical studies on N = 3381 participants, reporting on 35 effect sizes. A (...) multilevel approach to meta-analysis was applied to test the association between grandparental support and maternal mental health. The results showed a small, statistically significant association (r =.16; 95% CI: 0.09–0.25). A moderator test indicated that the association was stronger for studies reporting on support from the maternal grandmother in particular (r =.23; 95% CI: 0.06–0.29). Our findings suggest that involved grandparents, in particular mother’s own mother, constitute a protective factor for the development of maternal postpartum mental health problems. These findings have clear implications for interventions. Future studies should examine whether stimulating high-quality support from grandparents is a fruitful avenue for enhancing maternal postpartum mental health. (shrink)

Humans have been called “cooperative breeders” because mothers rely heavily on alloparental assistance, and the grandmother life stage has been interpreted as an adaptation for alloparenting. Many studies indicate that women invest preferentially in their daughters’ children, but little research has been conducted where patrilocal residence is normative. Bangladesh is such a place, but women nevertheless receive substantial alloparental investment from the matrilateral family, and child outcomes improve when maternal grandmothers are alloparents. To garner this support, women must maintain contact (...) with their natal families. Here, the visiting behavior of 151 interviewed mothers was analyzed. Despite the challenges of patrilocality and purdah, almost all respondents visited their own mothers, and mothers-in-law were visited far less. This contrast persists in analyses controlling for proximity, respondent age, postmarital residence, family income, and marital status. These results affirm the importance women place on matrilateral ties, even under a countervailing ideology. (shrink)

Many studies in Western societies show a pattern of discriminative grandparental investment as follows: maternal grandmothers (MGMs) > maternal grandfathers (MGFs) > paternal grandmothers (PGMs) > paternal grandfathers (PGFs). This pattern is in line with the expectation from evolutionary reasoning. Yet whether or not this pattern applies in China is in question. The present study was based on a questionnaire survey at a university in Central China (N = 1,195). Results show that (1) when grandparent–grandchild residential distance during grandchildren’s childhood (...) is controlled, in the case of grandsons and granddaughters as a whole and granddaughters only, both grandparental caregiving and grandchildren’s emotional closeness to grandparents display a rank order of MGM > MGF > PGM > PGF, but in the case of grandsons only, this order is not statistically significant. (2) There are stable relationships between grandparental caregiving/grandchildren’s emotional closeness and residential distance/similarity in appearance. (3) The effects of residential distance on either PGFs’ or PGMs’ caregiving exceed those on either MGFs’ or MGMs’. (4) The PGF and PGM prefer grandsons to granddaughters in their caregiving, whereas the MGF and MGM do not have a sex preference, and (5) the fact that the PGF and PGM invest more in grandsons than in granddaughters does not depend on grandsons’ duration of living in a rural area. Our results suggest that (1) in general, the Chinese display a pattern of differential grandparental investment predicted by an evolutionary perspective, (2) the evolutionary perspective that combines the two factors of paternal uncertainty and sex-specific reproductive strategies is applicable to grandparental investment in China, and (3) the traditional son-preference culture also plays some role in affecting grandparental investment in China, though the roles of culture and urban–rural cultural difference should not be exaggerated. (shrink)

Dispersal of individuals from their natal communities at sexual maturity is an important determinant of kin association. In this paper we compare postmarital residence patterns among Pumé foragers of Venezuela to investigate the prevalence of sex-biased vs. bilateral residence. This study complements cross-cultural overviews by examining postmarital kin association in relation to individual, longitudinal data on residence within a forager society. Based on cultural norms, the Pumé have been characterized as matrilocal. Analysis of Pumé marriages over a 25-year period finds (...) a predominant pattern of natalocal residence. We emphasize that natalocality, bilocality, and multilocality accomplish similar ends in maximizing bilateral kin affiliations in contrast to sex-biased residential patterns. Bilateral kin association may be especially important in foraging economies where subsistence activities change throughout the year and large kin networks permit greater potential flexibility in residential mobility. (shrink)

Based on historical data pertaining to the Krummhörn population (eighteenth and nineteenth centuries, Germany), we compared reproductive histories of mothers according to whether the maternal grandmother (MGM) or the paternal grandmother (PGM) or neither of them was resident in the parents’ parish at the time of the mother’s first birth. In contrast to effects of PGMs, we discovered conditional differences in the MGM’s effects between landless people and wealthier, commercial farmers. Our data indicate that the presence of the MGM only (...) lowers the woman’s age at marriage (AAM) and her age at the birth of her first child (AFB) in the case of landless families. However, among commercial farmers, who can generally be characterized by a lower AAM and AFB, we found opposite tendencies for the MGM’s effect leading to a relatively small delay in AAM and AFB. Moreover, we also analyzed differences in the completed fertility (i.e., children ever born: CEB). Results indicate that landless families in general do have fewer CEB compared with commercial farmers except for those families in which the MGM has been present. Emphasizing that the adaptiveness of investment decisions should depend on the interaction of genetic, lineage-specific (intrinsic) and ecologically imposed (extrinsic) constraints, we conclude that kin strategies consequently address different fitness components under different conditions. (shrink)

What causes adolescents to develop consumer’ ethical beliefs? Prior research has largely focused on the negative influence of peers and negative patterns of parent–child interactions to explain risky and unethical consumer behaviors. We take a different perspective by focusing on the positive support of parents and peers in adolescent social development. An integrative model is developed that links parental and peer support with adolescents’ self-worth motives, their materialistic tendencies, and their consumer ethical beliefs. In a study of 984 adolescents, we (...) demonstrate support for a sequential mediation model in which peer and parental support is positively related to adolescents’ self-esteem and feelings of power, which are each associated with decreased materialism as a means of compensating for low self-worth. This reduced materialism is, in turn, associated with more ethical consumer beliefs. (shrink)

Graphical AbstractPheomelanogenesis may have evolved as an excretory mechanism to remove excess cysteine, and in humans this might potentially confer a greater ability to avoid disease such as Parkinson's and Alzheimer's disease, in which excess cysteine is a contributory cause.

I argue that views of human rationality are strongly affected by the adoption of a two minds theory in which humans have an old mind which evolved early and shares many features of animal cognition, as well as new mind which evolved later and is distinctively developed in humans. Both minds have a form of instrumental rationality—striving for the attainment of goals—but by very different mechanisms. The old mind relies on a combination of evolution and experiential learning, and is therefore (...) driven entirely by repeating behaviours which succeeded in the past. The new mind, however, permits the solution of novel problems by reasoning about the future, enabling consequential decision making. I suggest that the concept of epistemic rationality—striving for true knowledge—can only usefully be applied to the new mind with its access to explicit knowledge and beliefs. I also suggest that we commonly interpret behaviour as irrational when the old mind conflicts with the new and frustrates the goals of the conscious person. (shrink)

El objetivo fue examinar el valor del ocio lúdico y cultural compartido entre abuelos y nietos para el bienestar de ambas generaciones. Se utilizaron técnicas cuantitativas -cuestionario ad hoc administrado a 1080 estudiantes de primaria- y cualitativas-2 grupos de discusión-. Las actividades lúdicas y culturales fueron preferentesen el ocio compartido, practicándose más con las abuelas. Como aportacionesdestacaron el incremento de la comunicación, la diversión, el aprendizaje mutuo y elbienestar afectivo. La práctica de ocio cultural y lúdico intergeneracional se asociópositivamente con (...) la valoración de una mejor relación entre nietos y abuelos. (shrink)

A major trend in foster care in developed countries over the past quarter century has been a shift toward placing children with “kin” rather than with unrelated foster parents. This change in practice is widely backed by legislation and is routinely justified as being in the best interests of the child. It is tempting to interpret this change as indicating that the child welfare profession has belatedly discovered that human social sentiments are nepotistic in their design, such that kin tend (...) to be the most nurturant alloparents. Arguably, however, the change in practice has been driven by demographic, economic, and political forces rather than by discovery of its benefits. More and better research is needed before we can be sure that children have actually benefitted. (shrink)

Breastfeeding is one important form of maternal investment that is influenced by support from kin and non-kin. This paper investigates who provides support for breastfeeding mothers and their children, what type of support they provide, and how support impacts breastfeeding duration. The data were derived from a survey of 594 American mothers and were analyzed using quantitative methods, including Cox regression. Analyses indicate that mothers receive significant support, particularly from spouses and maternal grandmothers. More frequent breastfeeding discussions with La Leche (...) League and maternal grandfathers were associated with longer duration, whereas discussions with physicians were associated with shorter breastfeeding duration. Results indicate that consulting others specifically about breastfeeding may influence breastfeeding decisions. The results are consistent with the idea that social support may influence breastfeeding duration and that some types of support are more influential than others. Furthermore, support persons should be educated about breastfeeding to prevent early weaning. (shrink)