Does the kin orientation of a British woman�s social network influence her entry into motherhood?

BACKGROUND The influence of family and friends on an individual's fertility has long been an important topic within demography. Researchers who focus on social network effects and evolutionary demography have shown a renewed interest in this issue in recent years. However, only a few studies have been conducted in contemporary low-fertility, resource-rich settings. OBJECTIVE This study investigates whether a British woman's entry into motherhood (i.e., her first birth) is influenced by the kin orientation of her close social network. Specifically, we test the prediction derived from evolutionary theory that individuals with a kin-oriented network will have higher fertility than those with fewer relatives in their close social networks. We consider two potential proximate mechanisms by which kin may influence fertility. First, relatives could provide practical resources, such as childcare, which reduce the costs of reproduction, thereby increasing fertility. Second, family members might communicate relatively pro-natal messages that could help to "persuade" childless women to become mothers. METHODS We use data from the British Household Panel Study (1992 to 2003), and base the degree of kin orientation on the number of relatives a woman includes when identifying her three closest non-household associates. We conduct a discrete-time event history analysis to measure the risk of firstbirth, controlling for household composition and socio-economic background.RESULTS We find that when a woman has more kin in her close social network, her risk of havinga first birth increases at all ages. This suggests that relatives may influence fertility behaviour in this contemporary resource-rich population. Both of our proposed proximate mechanismsmay be important in driving this effect. © 2013 Paul Mathews & Rebecca Sear

Do preceding questions influence the reporting of childbearing intentions in social surveys?

For demographers fertility intentions are a long standing source of both interest and scepticism. Scepticism has been expressed because fertility intentions regularly fail to precisely predict fertility and because they are liable to change across the life course. Here we demonstrate an additional consideration: simply changing the questions that precede fertility intentions questions can have a significant influence on responses. We illustrate this risk using a series of randomised experiments with different preceding questions; first, on mortality and risk in two convenience samples of UK undergraduate students. Secondly, we will present provisional results from a ground-breaking longitudinal experiment where the manipulated preceding questions are on close family and friends. As far as we are aware this later study is the first time that question ordering experiment looking at fertility intentions has been embedded in a representative survey, and the first longitudinal measurement of preceding-question effects using the same individuals

Area-level mortality and morbidity predict ‘abortion proportion’ in England and Wales

Life history theory predicts that where mortality/morbidity is high, earlier reproduction will be favoured. A key component of reproductive decision-making in high income contexts is induced abortion. Accordingly, relationships between mortality/morbidity and ‘abortion proportion’ (proportion of conceptions ending in abortion) are explored at small-area (‘ward’) level in England and Wales. It is predicted that where mortality/morbidity is high, there will be a lower ‘abortion proportion’ in younger women (< 25 years), adjusting for education, unemployment, income, housing tenure and population density. Results show that this prediction is supported: wards with both shorter life expectancy and a higher proportion of people with a limiting long-standing illness have lower abortion proportions in under 25 s. In older age bands, in contrast, elevated mortality and morbidity are mostly associated with a higher ‘abortion proportion’. Further, morbidity appears to have a larger effect than mortality on ‘abortion proportion’ in the under-25 age band, perhaps because a) morbidity is be more salient than mortality in high-income contexts, and/or b) young women are influenced by health of potential female alloparents when scheduling fertility

Do grandparents compete with or support their grandchildren? In Guatemala, paternal grandmothers may compete, and maternal grandmothers may cooperate.

Previous research has found that the presence of grandparents, particularly grandmothers, is often positively associated with child survival. Little research has explored the potential mechanisms driving these associations. We use data from rural Guatemala to test whether contact with and direct investment (advice and financial) from grandparents is associated with child health, proxied by height. Our results demonstrate the complexity of family relationships and their influence on child health, suggesting that both cooperative and competitive relationships exist within the family. The clearest evidence we find for grandparental influence is that having a living paternal grandmother tends to be negatively associated with child height. By contrast, contact with maternal kin appears broadly to be beneficial for child height, although these relationships are weaker. These patterns are mirrored in maternal body mass index, suggesting grandparental influence acts partly through maternal health. These findings support the hypotheses that, under conditions of limited resources, family relationships may be competitive within the family lineage which shares the same resource base, but cooperative when there are few costs to cooperation. Finally, financial assistance from maternal grandfathers is positively correlated with infant length but negatively with the height of older children, perhaps because the receipt of financial support is an indication of need. The provision of advice shows no associations with child height

Does grandparental help mediate the relationship between kin presence and fertility?

Previous research suggests that kin availability may be correlated with reproductive outcomes, but it is not clear that a causal relationship underlies these findings. Further, there is substantial variation in how kin availability is measured. OBJECTIVE We attempt to identify whether different measures of kin availability influence how kin affect reproductive outcomes and whether the effect of kin on reproductive outcomes is driven by the help that they provide. METHODS Using data from the Indonesia Family Life Survey (1993, 1997, 2000, 2007), we compare the survival of parents and parents-in-law, their co-residence, geographic proximity, contact frequency, and helping behavior in predicting fertility outcomes, and test a hypothesized causal pathway linking kin availability to reproduction via helping behavior. RESULTS We find different results if we operationalize parental availability as survival or co-residence, suggesting that these measures cannot be used interchangeably. Receiving help from parents or parents-in-law has a positive effect on progression to birth when women have fewer than three living children. Path analyses show that geographic proximity is associated with contact frequency, which in turn influences helping behavior. Kin help has a positive effect on progression to giving birth for all parental categories, but the effects are strongest for mothers-in-law. CONCLUSION In Indonesia, kin availability has a positive effect on fertility only when kin provide help, suggesting that there is a causal relationship between kin availability and fertility which is mediated via the provision of help

How might life history theory contribute to life course theory?

In this commentary, we consider how evolutionary biology’s life history theory (LHT) can be integrated with life course theorizing, to the benefit of both endeavors. We highlight areas where it can add value to existing work in life course theory (LCT), focusing on: how it can add an extra level of explanation, which may be helpful in understanding why individuals focus on their own health and happiness (or why they don’t); how insights from comparative work, both across species and across all kinds of human populations, can inform LCT; and how social and biological researchers can come together fruitfully to make progress on the tricky issue of understanding human agenc

Modernizing Evolutionary Anthropology : Introduction to the Special Issue.

Evolutionary anthropology has traditionally focused on the study of small-scale, largely self-sufficient societies. The increasing rarity of these societies underscores the importance of such research yet also suggests the need to understand the processes by which such societies are being lost-what we call "modernization"-and the effects of these processes on human behavior and biology. In this article, we discuss recent efforts by evolutionary anthropologists to incorporate modernization into their research and the challenges and rewards that follow. Advantages include that these studies allow for explicit testing of hypotheses that explore how behavior and biology change in conjunction with changes in social, economic, and ecological factors. In addition, modernization often provides a source of "natural experiments" since it may proceed in a piecemeal fashion through a population. Challenges arise, however, in association with reduced variability in fitness proxies such as fertility, and with the increasing use of relatively novel methodologies in evolutionary anthropology, such as the analysis of secondary data. Confronting these challenges will require careful consideration but will lead to an improved understanding of humanity. We conclude that the study of modernization offers the prospect of developing a richer evolutionary anthropology, by encompassing ultimate and proximate explanations for behavior expressed across the full range of human societies

Are mothers less likely to breastfeed in harsh environments? Physical environmental quality and breastfeeding in the Born in Bradford study.

We use the United Kingdom's Born in Bradford study to investigate whether women in lower quality environments are less likely to breastfeed. We use measures of physical environmental quality (water disinfectant by-products [DBPs], air pollution, passive cigarette smoke, and household condition) alongside socio-economic indicators, to explore in detail how different exposures influence breastfeeding. Drawing on evolutionary life history theory, we predict that lower environmental quality will be associated with lower odds of initiating, and higher hazards of stopping, breastfeeding. As low physical environmental quality may increase the risk of adverse birth outcomes, which may in turn affect breastfeeding chances, we also test for mediation by gestational age, birthweight, head circumference, and abdominal circumference. Our sample is composed of mothers who gave birth at the Bradford Royal Infirmary in West Yorkshire between March 2007 and December 2010 for whom breastfeeding initiation data was available. Analyses were stratified by the two largest ethnic groups: White British (n = 3,951) and Pakistani-origin (n = 4,411) mothers. After controlling for socio-economic position, Pakistani-origin mothers had lower chances of initiating and higher chances of stopping breastfeeding with increased water DBP exposure (e.g., OR for 0.03-0.61 vs. <0.02 μg/day dibromochloromethane exposure 0.70 [0.58-0.83], HR 1.16 [0.99-1.36]), greater air pollution exposure predicted lower chances of initiation for both ethnic groups (e.g., OR for 10 μg/m3 increase in nitrogen dioxide 0.81 [0.66-0.99] for White British mothers and 0.79 [0.67-0.94] for Pakistani-origin mothers) but also a reduced hazard of stopping breastfeeding for White British mothers (HR 0.65 [0.52-0.80]), and exposure to household damp/mould predicted higher chances of breastfeeding initiation amongst White British mothers (OR 1.66 [1.11-2.47]). We found no evidence that physical environmental quality effects on breastfeeding were mediated through birth outcomes amongst Pakistani-origin mothers and only weak evidence (p < 0.10) amongst White British mothers (exposure to passive cigarette smoke was associated with having lower birthweight infants who were in turn less likely to be breastfed whereas greater air pollution exposure was associated with longer gestations and in turn reduced hazards of stopping breastfeeding). Overall, our findings suggest that there is differential susceptibility to environmental exposures according to ethnicity. Although the water DBP results for Pakistani-origin mothers and air pollution-initiation results for both ethnic groups support our hypothesis that mothers exhibit reduced breastfeeding in poorer quality environments, several physical environmental quality indicators showed null or positive associations with breastfeeding outcomes. We consider physiological explanations for our findings and their implications for life history theory and public health policy