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Daughters increase longevity of fathers, but daughters and sons equally reduce longevity of mothers

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Abstract

Reproduction is energetically and physiologically expensive, and an individual investing resources into producing offspring should suffer costs such as deterioration in health condition and possibly shorter life span. Since the energetic and nutritional demands of pregnancy and breastfeeding render reproductive costs much higher in women than in men, women with a large number of children should show signs of deterioration in condition, while men with large families should not. However, whether reproductive costs reduce longevity in women is still questionable, and in men this issue has not been adequately addressed. In addition, since sons are energetically more expensive to produce than daughters, having sons should have a more pronounced negative impact on maternal longevity than having daughters. Here we document a striking disparity in the impact of children on the life span of mothers and fathers in a Polish rural population. We show for the first time that number of daughters was positively related to a longer life span of their fathers, increasing their longevity on average by 74 weeks per daughter born, while number of sons did not have a significant effect on paternal longevity. In contrast, in women, the number of daughters and number of sons reduced maternal longevity and did so to the same extent, on average by 95 weeks per son or daughter, indicating that for women, the costs of having sons and daughters are similar.

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... Neither of these omissions presents any evidence in favour of HLJ's original conclusion of a large differential effect of sex of offspring on maternal longevity. Neither do Jasienska et al. (2006) whose findings it is suggested that we misrepresented along with those in Van de Putte et al. (2004) and Hurt et al. (2006). In the words of HLJ: 'Jasienska et al. (2006) demonstrated that in rural Polish population mothers with many sons were short-lived but also that daughters born had a similar association with maternal mortality.' ...
... Neither do Jasienska et al. (2006) whose findings it is suggested that we misrepresented along with those in Van de Putte et al. (2004) and Hurt et al. (2006). In the words of HLJ: 'Jasienska et al. (2006) demonstrated that in rural Polish population mothers with many sons were short-lived but also that daughters born had a similar association with maternal mortality.' The authors also complain that we do not question the findings of Jasienska et al. (2006) based on their small sample size. ...
... In the words of HLJ: 'Jasienska et al. (2006) demonstrated that in rural Polish population mothers with many sons were short-lived but also that daughters born had a similar association with maternal mortality.' The authors also complain that we do not question the findings of Jasienska et al. (2006) based on their small sample size. But our paper is a replication of Helle et al. (2002), not Jasienska et al. (2006, which was only mentioned in passing as part of a literature review. ...
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We are grateful for the opportunity to respond to Helle, Lumma and Jokela's (henceforth HLJ; Helle et al. 2010) comment on our work. HLJ attribute to us the conclusion that the results in Helle et al. (2002) were ‘probably false positive owing to smaller sample size’. This is puzzling, for two reasons. First, from a purely statistical point of view, the probability of rejecting a true null (i.e. to obtain a false positive) does not depend on sample size. Second, we never made any statement to this effect. In fact, neither of our two papers uses the phrase ‘false positive’ or any comparable language. Despite the fact that the conclusion attributed to us by HLJ is inaccurate, the choice of language cuts to the heart of our differences of opinion.
... In recent years, several studies have shown the significant impact of father-daughter relationships on both fathers and daughters and across society (McMunn et al. 2015;Nielsen 2020;Sağkal et al. 2018). Positive relationships with one s father can have a profound effect on the well-being, academic journey, economic status, and the mental and physical well-being of children, notably daughters (Jasienska et al. 2006). For example, Nielsen (2020) found that irrespective of any economic or educational background, race, or religion, daughters with strong relationships with their fathers perform better in school and are more emotionally resilient as adults. ...
... The effects of having a daughter are also found to have reciprocal benefits for fathers, as studies have found that men with daughters are more likely to develop values of gender equity, support gender equitable policies and practices, and be more aware and favourable of women s issues and rights (Dahl et al. 2012;Glynn and Sen 2015;Oswald and Powdthavee 2010;Shafer and Malhotra 2011;Sharrow et al. 2018;Washington 2008). Additionally, a study by Jasienska et al. (2006) found that the number of daughters was positivel related to [the] longer lifespan of their fathers (422). As such, an engaged and healthy father-daughter relationship has beneficial effects across a wide spectrum for fathers, daughters, families, and communities. ...
Article
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Research supports that the positive involvement of fathers in caregiving activities cultivates family cohesion and fosters the emotional well-being of fathers and their families. However, there are limited community-based resources that support and celebrate the development of nurturing fatherhood and focus on strengthening father-daughter relationships. In collaboration with diverse communities in Calgary, Canada, a local network launched a community-based and culturally relevant program, Honouring Fathers and Daughters, to promote positive fatherhood roles and to celebrate both nurturing fatherhood practices and the significance of father-daughter relationships. Participants (N=65), from ethnically and socioeconomically diverse backgrounds, including 19 fathers, 17 mothers, and 29 children, joined the program. A community-based research approach (CBR) was employed to gather participant responses through feedback forms. Through qualitative analysis, responses indicated three key themes: valuing and appreciating father-daughter relationships, the need for social and cultural spaces for the engagement and transformation of fathers, and the importance of providing opportunities for fathers to learn new strategies for parenting and bonding with their daughters. This article highlights the importance of community-based engagement programs for nurturing father-daughter relationships and provides insights for communities.
... Some authors maintain that sons induce a higher physiological cost than daughters due to their greater corporal mass and higher metabolism (Helle et al., 2002). Whether reproductive costs reduce longevity in women is still a question for debate (Lycett et al., 2000;Jasieńska et al., 2006;Le Bourg, 2007;Gagnon et al., 2009). ...
... Based on a small sample of parish records from southern Poland, Jasieńska et al. (2006) stated that the number of daughters was positively related to the longer life span of their fathers, while sons did not have a significant effect on paternal longevity. In women, the number of both daughters and sons reduced maternal longevity. ...
Article
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Using data from parish and civil registers in a rural community in northwest Spain (Los Nogales), family reconstitution provided 1502 complete reproductive histories, of which 584 corresponded to first marriages of women dying after their 50th birthday. A homogeneous sample consisting of women married in the period 1877-1899 (N=311) provided information concerning their reproductive performance, including ages at first and last maternity and number of children born alive and surviving, which was related to the mother's post-menopausal longevity, also considering premarital fertility and her marital status (widow/married). The results obtained indicate that mothers with a lower proportion of children dying before the first birthday and the age of 15 (mainly males) have a greater post-reproductive longevity. Moreover, women with a more protracted end to their reproductive period and greater fertility live for more years beyond their 50th birthday. These results do not prove a causality between maternal longevity and more successful reproduction; instead, they are indicative of a holistic condition of health. A wide spectrum of favorable biological and environmental factors will have positive consequences for a woman's life trajectory, affecting both her reproductive performance and her own likelihood of surviving.
... High reproductive effort accompanied by high energy flux during the reproductive period may intensify trade-offs incurred by reproductive processes later in post-reproductive life [1]. Indeed, previous studies conducted in this population demonstrated a reduction in maternal longevity in association with number of children [19]. ...
... Life history theory predicts trade-offs between reproductive effort and longevity when energy resources are limited [47][48]. Accordingly, lifetime parity was demonstrated to shorten lifespan in some but not all energetically constrained environments [19,[49][50][51][52]. Lifetime parity and gravidity has been also observed to be a risk factor to many diseases associated with higher mortality in post reproductive life such as cardiovascular disease, some forms of cancer, insulin resistance, diabetes, and Alzheimer's disease [53][54][55][56]. ...
Article
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Life history theory predicts trade-offs between reproductive effort and maternal survivorship in energy-restricted environments. However, empirical evidence for the positive association between maternal mortality and reproductive effort from energetically challenged human populations are mixed and physiological mechanisms that may underlie this association are poorly understood. We hypothesized that increases in aerobic metabolism during repeated periods of pregnancy and lactation result in increased oxidative stress that may contribute to somatic deterioration, vulnerability to illness, and accelerated aging. We therefore predicted that lifetime gravidity and parity would be related to levels of biomarkers of oxidative stress, as well as antioxidative defence enzymes in post-menopausal women. Our hypothesis was supported by positive linear associations between levels of 8-OHdG, a biomarker of DNA oxidative damage (β=0.21, p<0.05), levels of antioxidative defence enzyme Cu-Zn SOD (β=0.25, p<0.05), and number of lifetime pregnancies. Furthermore, independent of age and health status, post-menopausal women with higher gravidity and parity (>=4 pregnancies per lifetime) had 20% higher levels of 8-OHdG and 60% higher levels of Cu-Zn SOD compared to women with lower gravidity and parity (<4 pregnancies per lifetime). Our results present the first evidence for oxidative stress as a possible cost of reproductive effort in humans.
... There has been little research into whether the sex composition of the children affects parents' mortality in western contemporary societies. A study by Jasienska, Nenko and Jasienski [10] concludes that daughters reduce men's mortality whereas both sons and daughters increase women's mortality, and do so to the same extent. However, this investigation includes only 102 women and 163 men born between 1894 and 1937. ...
... The analysis is based on discretetime hazard models, estimated for the years 1980-2008 for women and men born after 1935 using register data that encompasses the entire Norwegian population. As suggested by earlier studies [10], the effect of a certain sex composition is not necessarily the same for mothers and fathers, so the models are estimated separately for women and men. Furthermore, the effect may vary with certain characteristics of the parents. ...
Article
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Background This study explores the relationship between children’s sex composition and parents’ mortality in a contemporary western society. It improves on earlier research by using a larger and more representative dataset – constructed from registers and encompassing the entire Norwegian population. Methods The analysis is based on discrete-time hazard models, estimated for the years 1980–2008 for women and men born after 1935. Results When operationalising sex composition as the “number of boys”, coefficients are insignificant in all specifications. However, when considering the three categories “only boys”, “only girls” and “mixed sex”, I find a small but significant disadvantage of having only girls, compared to having at least one child of each sex, for mothers of two or more children. Having only daughters is associated with a mortality disadvantage compared to having only sons for mothers of two children, but a mortality advantage among mothers with four children. Among women who gave birth to their first child as teenagers, those who have only sons have relatively high mortality. I also find an excess mortality both for mothers of only girls and mothers of only boys in the period 1980–1989. Conclusion These results lend some support to the notion that there is a larger benefit of the first son or daughter than the later children of the same sex, and especially in the earliest decade of the study period.
... However, parenting is a factor that may have a long-term impact on many aspects of behavior, physiology, and health. In women, due to high energetic and physiological costs of reproduction, high parity is related to increased risk of several diseases (Hinkula, Kauppila, Nayha, & Pukkala, 2006; Skilton, Serusclat, Begg, Moulin, & Bonnet, 2009) and even to a reduced longevity (Jasienska, 2009; Jasienska, Nenko, & Jasienski, 2006; Le Bourg, 2007; Jasienska, 2013). In men, fathers differ from nonfathers in their social connections, family relationships, and work behavior (Eggebeen & Knoester, 2001), and the number of children is related to health risk factors, for example, smoking cessation (Jarvis, 1996) and subsequent risk of obesity (Bakhshi et al., 2008; Weng, Bastian, Taylor, Moser, & Ostbye, 2004). ...
... In men, fathers differ from nonfathers in their social connections, family relationships, and work behavior (Eggebeen & Knoester, 2001), and the number of children is related to health risk factors, for example, smoking cessation (Jarvis, 1996) and subsequent risk of obesity (Bakhshi et al., 2008; Weng, Bastian, Taylor, Moser, & Ostbye, 2004). In Polish rural populations, the number of daughters was positively related to the longevity of their fathers (Jasienska et al., 2006). It is, therefore, likely that having children may influence paternal health and physiology, including T levels, not only through direct physical contact with children but also during years when such contacts are no longer frequent. ...
Article
Most research shows that fatherhood is related to reduced testosterone (T) levels, but relationships between the number of children and T levels are not addressed. In humans, paternal care usually involves obtaining adequate resources to support children, which may require engaging in male-male competition and maintaining high T levels. We hypothesize that T levels in fathers should increase with increasing family size. In 78 Polish men, aged 30 to 77 years, the number of children was significantly correlated with paternal T levels, but the direction of this relationship was dependent on the fathers' education. In agreement with our hypothesis, in men with below-college education, T levels increased with increasing number of children. In contrast, in men with college education, the number of children was negatively related to paternal T levels. Drop in T levels throughout the day tended to be less pronounced the more children fathers had, irrespective of their educational level. Our results suggest that a hypothesis of simple trade-offs between mating and parenting effort may be too simplistic to explain changes in testosterone response to parenting in human males. In order to understand functional response of changes in T levels, it is crucial to account for family size and socioeconomic factors. However, due to the cross-sectional study design, we cannot exclude the possibility that T levels influenced reproductive behavior (rather than vice versa) and thus the number of children produced by men.
... Such support has in earlier research indicated health advantages. [13][14][15] It has also been shown that childless older individuals receive less social support than parents do: In a review, one of the major findings was that old childless people who were in poor health and lived alone faced potential support deficits. 16 Related to the hypothesis of a greater need of social support in old age and the help from children for such needs, is the role of the gender of the child for parental mortality. ...
... Some studies found no association with the gender of the child, 18 19 while other found that daughters are more favourable, 20 sometimes for fathers only. 13 In a study on Swedish data, the protective effect of having a daughter was detected only among one-child parents, but not for parents with several children, 14 which is in line with a Norwegian study. 15 However, none of these studies followed individuals into ages above average LE. ...
Article
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Background It is known that parents have lower mortality than childless individuals. Support from adult children to ageing parents may be of importance for parental health and longevity. The aim of this study was to estimate the association between having a child and the risk of death, and to examine whether the association increased at older ages when health starts to deteriorate and the need of support from a family member increases. Methods In this nationwide study, all men and women (born between 1911 and 1925 and residing in Sweden), as well as their children, were identified in population registers and followed over time. Age-specific death risks were calculated for each calendar year for individuals having at least one child and for individuals without children. Adjusted risk differences and risk ratios were estimated. Results Men and women having at least one child experienced lower death risks than childless men and women. At 60 years of age, the difference in life expectancy was 2 years for men and 1.5 years for women. The absolute differences in death risks increased with parents' age and were somewhat larger for men than for women. The association persisted when the potential confounding effect of having a partner was taken into account. The gender of the child did not matter for the association between parenthood and mortality. Conclusions Having children is associated with increased longevity, particularly in an absolute sense in old age. That the association increased with parents' age and was somewhat stronger for the non-married may suggest that social support is a possible explanation.
... For example, in historical populations, some studies have been able to establish the expected negative effects of high total reproductive effort on female postreproductive longevity (e.g. Gagnon et al. 2009;Jasienska et al. 2006a;Westendorp and Kirkwood 1998); but also many studies find no association or a positive correlation between total number of children and post-reproductive survival (Korpelainen 2000;Le Bourg et al. 1993;Müller et al. 2002); and sometimes this trade-off is manifested only among the poorest women (Dribe 2004;Lycett et al. 2000). Similar mixed results arise from studies on the association between total family size and longevity in contemporary populations (e.g. ...
... Doblhammer and Oeppen 2003;Helle et al. 2004; but see Penn and Smith 2007) or positive effects of offspring of only one sex (e.g. Jasienska et al. 2006a). Across countries, however, birthrates are indeed related to a sex difference in lifespan: birthrate per female explains 17% of the variation in relative sex differences in lifespan across countries, and low birthrate results in females living relatively longer than males (Maklakov 2008). ...
Chapter
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The life history of women is characterized by several unusual patterns: women have a relatively late age at maturity compared to other primates, they produce offspring at short inter-birth intervals, and typically have many dependent offspring of varying ages to care for simultaneously. Women then lose their potential to bear children at menopause but can live a few decades afterwards. Such a reproductive strategy involves several trade-offs and costs of reproduction to future success that have to be optimized across the entire lifespan. This chapter summarizes evidence from humans on the costs of reproduction. First, I discuss the short-and long-term effects of investment in reproduction on the survival patterns of individuals. Second, I address how current reproductive investment affects the ability to invest in future reproductive events. Third, I review the evidence for such costs of reproduction and trade-offs changing with the age of the individual and across different environments. Trade-offs are predicted to be most severe among the very young and senescing females, and when resources are limited. Finally, I investigate the heritable genetic basis for individual differences in the consequences of reproduction, and how heritabilities and genetic trade-offs between traits vary with age and across environmental conditions.
... Certain scholars believe that the trade-off relationship between the number of births and longevity does not exist or that the two factors are positively correlated [4,[19][20][21]. Using the data of 6359 women born in the Netherlands (1850-1910), Kaptijn et al. [6] found no trade-off between fertility and life span during the epidemic transition period. ...
... Harrell, Smith, and Mineau [31] further found a significant correlation between children's gender and mothers' life expectancy. Jasienska, Nenko, and Jasienski [19] found that the number of daughters and sons had a negative impact on the life span of mothers, based on data from rural Poland; for every additional son or daughter, a mother's life span would be reduced by 95 weeks. Zeng, Brasher, Gu, and Vaupel [32] used CLHLS data and found that having daughters reduced the risk of death in older adults, in contrast to sons. ...
Article
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Background This study evaluates the impact of fertility during the childbearing period on the longevity of older rural Chinese women and verifies whether any trade-off exists between women’s longevity and their number of children to provide empirical evidence for improving health intervention policies and formulating active fertility policies in low-fertility countries. Methods Based on the data of the deaths of 1623 older adults aged 65 and above during 2014–2018 in the Chinese Longitudinal Healthy Longevity Survey, this study explores the relationship between the number of children born and older rural women’s longevity using the ordinary least squares method. Furthermore, the impact of fertility on the longevity of men and women in rural and urban areas, along with other reproductive behaviours on older rural women’s longevity, were analysed. Results There was a significant negative correlation between the number of children born and women’s longevity (β = − 0.555, p < 0.05). Additionally, their longevity exhibited a decreasing trend with having birthed more sons and an increasing trend with more daughters. Age at first and last births had a significant positive relationship with rural women’s longevity; however, the effect of fertility on the longevity of older rural and urban men and older urban women was not significant. Conclusions It is confirmed that there is a trade-off between fertility and longevity for rural women in China. Future research should focus on compensating for the decline in female longevity caused by the number of children born and promote the concept of a healthy pregnancy, scientific nurture, and gender equality in fertility.
... Several recent studies have addressed the long-term costs and benefits of bearing and raising children. Looking at mothers and fathers who survived at least to age 45, maternal longevity was found to be negatively related to having sons (Helle et al. 2002; Hurt et al. 2006; Jasienska et al. 2006; Van De Putte et al. 2004) and positively related to having daughters (Beise and Voland 2002; Helle et al. 2002). Helle et al. found that having sons or daughters had no effect on paternal mortality, and Jasienska et al. found that having daughters increased paternal lifespan and decreased maternal lifespan. ...
... t on parental longevity at all, it is mediated by other sociocultural factors. Two additional studies considering more modern populations found differing results. Hurt et al. (2006) examined a rural Bangladesh population (1927–1998) and found that, after adjusting for the number of surviving sons, the number of sons born reduced maternal mortality. Jasienska et al. (2006) analyzed a rural Polish population (1886–2002). They found that the number of daughters increased paternal lifespan while the number of daughters and the number of sons reduced maternal lifespan. Because economic factors may suppress the potential negative effects of having sons on maternal life chances, Van De Putte et al. (2004) also ...
Article
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Using historical data from the Utah Population Database, this analysis finds significant, consistent, but small adverse mortality effects for mothers after age 50 who had mostly sons. Examination of age-dependent effects indicates that this association increases with mother’s age. Additionally, mothers who had mostly daughters faced mortality risks that increased with age. Offspring sex composition did not have a significant effect on paternal mortality. Interaction analyses were conducted to examine the effect of offspring sex composition with regard to historical period, residential location, socioeconomic status, and childhood survival. No other interactions were found to be statistically significant. Having mostly boys remained detrimental to maternal mortality regardless of childhood survival.
... Research testing the disposable soma theory in both historical and contemporary populations has thus far yielded mixed results (see Hurt et al. (2006b) for a review). The majority of studies that considered the influence of childbearing on later life for mothers and fathers have found a stronger positive relationship between total parity and mortality for women than men (Friedlander 1996;Christensen et al. 1998;Smith et al. 2002;Doblhammer and Oeppen 2003;Dribe 2004;Zeng and Vaupel 2004;Jasienska et al. 2006;Harrell et al. 2008). Westendorp andKirkwood (1998) andSmith et al. (2002), however, showed that this association applied to both women and men in Great Britain and in Utah (where the association was weaker for men), and some studies have documented no correlation between parity and longevity for either women or men (Le Bourg et al. 1993;Alter et al. 2002;Menken et al. 2003). ...
... Harrell et al. (2008) described an adverse mortality effect of sons for mothers but not fathers in Utah, with no substantial effect for daughters. In Poland, Jasienska et al. (2006) found that the number of daughters was associated with higher longevity for fathers, but not mothers. ...
Article
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We investigate the relationship between reproduction and functional health in later life among women and men in the resource-poor and gender-stratified setting of Ismailia governorate, Egypt. Analyses of survey data collected in 2003 show a statistically significant positive association between parity and difficulty with activities of daily living (ADLs), controlling for demographic and socio-economic factors and other co-morbid conditions. We also find that the number of daughters (but not sons) is associated with worse physical functioning, and this association is more pronounced for older fathers than for older mothers. Our results indicate that both biological and social pathways link fertility and later-life health in this context, and that prescribed familial roles may underlie the differential impact of sons and daughters on the health of mothers and fathers in later life.
... However, such scenarios fit poorly with the observed differences between birth cohorts, with each cohort living and reproducing across a range of later-life years and conditions, and yet displaying distinct differences according to their birth cohort. Second, previous studies on humans have shown that the costs of reproduction can be offspring sex-specific, with sons costing more to maternal longevity than daughters ([20], but see [86]). We did not focus on such sex-specific costs here, but instead measured the costs of reproduction by the number of born or raised offspring regardless of their sex. ...
... Many previous studies measuring the cost of reproduction on survival have used lifetime reproductive success as a measure of reproductive investment, and contrasted this with post-reproductive survival (e.g. [15,23,86]). Potential problems with this approach are that (i) it means excluding women who could suffer detrimental cost of reproduction during reproductive years and as a consequence die young (before 50 years of age), and (ii) this approach does not consider the contrasting effects of bearing children versus raising them to independence. ...
Article
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Reproduction is predicted to trade-off with long-term maternal survival, but the survival costs often vary between individuals, cohorts and populations, limiting our understanding of this trade-off, which is central to life-history theory. One potential factor generating variation in reproductive costs is variation in developmental conditions, but the role of early-life environment in modifying the reproduction-survival trade-off has rarely been investigated. We quantified the effect of early-life environment on the trade-off between female reproduction and survival in pre-industrial humans by analysing individual-based life-history data for >80 birth cohorts collected from Finnish church records, and between-year variation in local crop yields, annual spring temperature, and infant mortality as proxies of early-life environment. We predicted that women born during poor environmental conditions would show higher costs of reproduction in terms of survival compared to women born in better conditions. We found profound variation between the studied cohorts in the correlation between reproduction and longevity and in the early-life environment these cohorts were exposed to, but no evidence that differences in early-life environment or access to wealth affected the trade-off between reproduction and survival. Our results therefore do not support the hypothesis that differences in developmental conditions underlie the observed heterogeneity in reproduction-survival trade-off between individuals.
... Mothers have an increased risk of cardiovascular diseases when having boys compared to girls, and increased cardiovascular mortality (Naess et al., 2017). A higher number of sons may also be associated with a shorter lifespan of mothers (Helle & Lummaa, 2013;Helle et al., 2002; but see: Beise & Voland, 2002;Jasienska et al., 2006). Having more sons may also contribute to increased levels of C-reactive protein (CRP) (Marttila et al., 2015), one of the markers of inflammaging, an age-related chronic sub-clinical systemic inflammatory state, which is associated with degenerative diseases and other aging-associated physiological changes (Franceschi et al., 2000;Pawelec et al., 2014). ...
... On the other hand, daughters may play a protective role for maternal health, canceling out the biological costs (i.e., pregnancy, lactation, and childcare) of having them. The Polish rural community had a traditional, paternalistic model of family structure: usually daughters helped mothers with household tasks and provided care for siblings (Jasienska et al., 2006). It has been also shown that daughters, more often than sons, provide care to their elderly mothers, including more social support and home maintenance (Ingersoll-Dayton et al., 1996). ...
Article
Objectives: Reproduction is costly, but sons and daughters differently influence maternal physiology, also in older age. In particular, having sons may negatively influence maternal health and may be associated with a shorter life span of mothers. Sons may also contribute to increased inflammaging, a chronic sub-clinical systemic inflammatory state characterized by elevated levels of serum inflammatory mediators. The aim of this study was to examine the impact of the total number of children, and the number of daughters and sons separately on concentrations of C-reactive protein (CRP), and proinflammatory cytokines such as interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α). Materials and methods: The participants were 378 women aged 45-92 who had 3.9 (SD 2.12, median = 4, range = 0-13) children, including 2.1 (SD 1.46, median = 2, range = 0-8) sons and 1.8 (SD 1.44, median = 2, range = 0-7) daughters on average. Results: We found a positive relationship between the overall number of children and IL-6 levels. CRP and IL-6 concentrations were positively associated with the number of sons but not with the number of daughters. Each son increased maternal CRP level by 11%, and IL-6 level by 6%. Neither the total number of children nor the number of daughters or sons were related to the TNF-α concentration. Discussion: Aging-associated inflammation in post-reproductive mothers with a higher number of sons supports the hypothesis of trade-offs between reproduction and health. Furthermore, these results provide new evidence contributing to the idea that having sons may have more detrimental effects on the maternal organism than having daughters.
... Some studies found negative associations between human fertility and longevity (or mortality), while others claimed no significant or even positive association (see [5][6][7] for literature review). Meanwhile, most studies found that the association between fertility and longevity is asymmetric by parental sex, with only mothers bearing the survival costs of reproduction [4,[8][9][10][11]. In a nutshell, empirical results seem to differ across studies due to variations in time periods, populations in different regions, sample selection criteria, modelling methods, and the choice of relevant controls [6,7,12,13]. ...
... Indeed, among other long-lived mammal species, early reproductive costs on either later reproduction or survival manifest even more during their reproductive period [56,57]. Imposing the age selection criteria S 2 without correcting for the mortality selection issue could bias the estimation results in many studies [6,11,35,37], even if their inferences to cover only the "post-reproductive" or "late-life" longevity and mortality have already been restricted (see [8,12,13] for discussions). Fig 1c illustrates the DAG of this model. ...
Article
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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.
... High reproductive effort accompanied by high energy flux during the reproductive period may intensify trade-offs incurred by reproductive processes later in post-reproductive life [1]. Indeed, previous studies conducted in this population demonstrated a reduction in maternal longevity in association with number of children [19]. ...
... Life history theory predicts trade-offs between reproductive effort and longevity when energy resources are limited [47][48]. Accordingly, lifetime parity was demonstrated to shorten lifespan in some but not all energetically constrained environments [19,[49][50][51][52]. Lifetime parity and gravidity has been also observed to be a risk factor to many diseases associated with higher mortality in post reproductive life such as cardiovascular disease, some forms of cancer, insulin resistance, diabetes, and Alzheimer's disease [53][54][55][56]. ...
Article
Full-text available
Life history theory predicts trade-offs between reproductive effort and maternal survivorship in energy-restricted environments. However, empirical evidence for the positive association between maternal mortality and reproductive effort from energetically challenged human populations are mixed and physiological mechanisms that may underlie this association are poorly understood. We hypothesized that increases in aerobic metabolism during repeated periods of pregnancy and lactation result in increased oxidative stress that may contribute to somatic deterioration, vulnerability to illness, and accelerated aging. We therefore predicted that lifetime gravidity and parity would be related to levels of biomarkers of oxidative stress, as well as antioxidative defence enzymes in post-menopausal women. Our hypothesis was supported by positive linear associations between levels of 8-OHdG, a biomarker of DNA oxidative damage (β = 0.21, p<0.05), levels of antioxidative defence enzyme Cu-Zn SOD (β = 0.25, p<0.05), and number of lifetime pregnancies. Furthermore, independent of age and health status, post-menopausal women with higher gravidity and parity (> = 4 pregnancies per lifetime) had 20% higher levels of 8-OHdG and 60% higher levels of Cu-Zn SOD compared to women with lower gravidity and parity (<4 pregnancies per lifetime). Our results present the first evidence for oxidative stress as a possible cost of reproductive effort in humans.
... Among mothers, the physiological costs of reproduction may have thus outweighed the help provided by the daughters (Jasienska et al. 2006). However, unlike the case of our sample size, Cesarini et al. (2009) did not question the findings of Jasienska et al. (2006) based on a sample size of 102 post-menopausal mothers and seem to take these results as evidence against the potential negative association between sons and maternal longevity. The literature review of Cesarini et al. (2009) on whether the number of sons born was related to their mother's lifespan is incomplete because there are more studies on this issue than is evident from their list of publications . ...
Article
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A recent paper by [Cesarini et al. (2009)][1] published in Proceedings B aimed at replicating our previous finding showing that in historical Sami mothers from Northern Scandinavia (mainly from Finland), each son born was associated with a reduction of 0.65 years of a mother's post-menopausal
... In a study from Poland, it was reported that each child born shortened the mother's lifespan by 95 weeks on average (Jasienska et al. 2006). In contrast, it was further found that children did not shorten the father's lifespan and that each daughter increased the father's longevity by 74 weeks on average although sons had no impact on the lifespan of fathers. ...
Article
Motherhood is a physiological status in which certain behavioural patterns are exhibited. Maintenance of the life of the species in mammals is dependent upon the presentation of motherhood services in a certain period that the child is dependent on the mother. Absence of the mother causes some deficiencies in social, behavioural and cognitive abilities, an abnormal development of the stress response system, learning and memory disorders, and later, inadequate motherhood skills of the mature offspring during their own maternity period. Because maternal care is extremely important for the survival of the child and thus, for the species to maintain, nature seems to have provided the development of a healthy mother-child relationship. Therefore, motherhood is programmed by the evolutionary process in the female brain before birth. It is certain that the brain of the mother is very different from the brains of the nulliparous women who are within the same age range, and is very sensitive to her own child's needs. For maternal behaviour to develop in human beings and animals, special neural networks, which are cooperatively developed by genetic, environmental and hormonal factors, are necessary. It also seems likely that non-genetic (epigenetic) transmission responsible for the internalization of maternal behaviours learned from the mother and hormonal exposure of the brain both during the foetal period, throughout the growth, and during the gestation of the woman as well as genetic factors, play an important role in the development of these maternal neural networks and systems. In this paper, which was prepared by obtaining the necessary publications by means of a search for the words related to motherhood in the PubMed search engine, the physical and mental changes that prepare females for motherhood and enable them to tolerate it will be reviewed.
... Reproduction is costly and in women high parity is often associated with poor health in older age (Humphries et al., 2001; Kvå le et al., 1994; Lawlor et al., 2003; Ness et al., 1993) and even the reduced lifespan (Dribe, 2004; Gagnon et al., in press; Jasienska et al., 2006; Smith et al., 2002). In women with good nutritional status, body mass often increases with the number of produced children (Cederlöf and Kaij, 1970; Harris and Ellison, 1997; Harris et al., 1997a,b; Rodrigues and Da Costa, 2001; Wolfe et al., 1997). ...
Article
In populations with limited resources, high-reproductive effort may lead to poor nutritional status of the mother (the maternal depletion syndrome), whereas in well-nourished populations woman's body weight tends to increase after each pregnancy. However, in affluent populations, women's body shape may change due to mobilization of polyunsaturated fatty acids (PUFAs) from the lower parts of their bodies to meet the needs of the developing child (the "covert maternal depletion"). We studied relationships between reproductive history traits and body size and shape for 296 rural, parous women in good nutritional status (mean body mass index, BMI = 27.9, SD = 5.94), aged 22-85 (mean 47.8, SD = 16.34) from southern Poland. Body mass adjusted for age, age of menarche, body height, and similarly adjusted BMI were each positively related to the number of children born by a woman (R = 0.13, P = 0.02 and R = 0.13, P = 0.02, respectively). Waist and hip circumferences, adjusted for confounders, did not show statistically significant relationships with the number of children. Moreover, groups with low and high parity did not significantly differ in hip/BMI and waist/BMI ratios, which were proposed to be indicators of covert form of maternal depletion (after controlling for overall body fatness and age). In conclusion, parity caused a slightly higher body mass and BMI later in life. However, parity did not lead to covert maternal depletion, perhaps because women in this population have relatively high-dietary intake of PUFAs.
... In Finnish Sami (Helle et al., 2002 ) and a Flemish village (Van de Putte et al., 2003), sons decreased maternal lifespan, while daughters did not. In four Polish small agricultural villages, however, analyses of parish records from 1886 to 2002 showed that both the number of sons and the number of daughters decreased maternal lifespan , and did so to the same degree (Jasienska et al., 2006a). Each additional son or daughter decreased maternal lifespan by 95 weeks, or almost two years, on average. ...
Article
In human females allocation of resources to support reproduction may cause their insufficient supply to other metabolic functions, resulting in compromised physiology, increased risks of diseases and, consequently, reduced lifespan. While many studies on both historical and contemporary populations show that women with high fertility indeed have shorter lifespans. This relationship is far from universal: a lack of correlation between fertility and lifespan, or even an increased lifespan of women with high fertility have also been documented. Reduced lifespan in women with high fertility may be undetectable due to methodological weaknesses of research or it may be truly absent, and its absence may be explained from biological principles. I will discuss the following reasons for a lack of the negative relationship, described in some demographic studies, between the number of children and lifespan in women: (1) Number of children is only a proxy of the total costs of reproduction and the cost of breastfeeding is often higher than the pregnancy cost but is often not taken into account. (2) Costs of reproduction can be interpreted in a meaningful way only when they are analyzed in relation to the overall energy budget of the woman. (3) Trade-offs between risks of different diseases due to reproduction yield different mortality predictions depending on the socio-economic status of the studied populations. (4) Costs of reproduction are related not only to having children but also to having grandchildren. Such intergenerational costs should be included in analysis of trade-offs between costs of reproduction and longevity.
... Reproduction during poor energetic conditions also worsens maternal nutritional status ( " the maternal depletion syndrome " ) (Merchant and Martorell, 1988; National Academy of Sciences Committee onPopulation, 1989;Tracer, 1991;Little et al., 1992;Winkvist et al., 1992;Miller et al., 1994;Pike, 1999;George et al., 2000), thus negatively affecting her future reproductive potential. Shorter life spans in women with many children also suggests that reproduction may indeed have negative long-term consequences for maternal health (Doblhammer, 2000;Helle et al., 2002;Dribe, 2004;Jasienska et al., 2006c). Reproductive suppression in response to temporary, poor environmental conditions serves to protect maternal condition and optimize lifetime reproductive output (Ellison, 2003b). ...
Chapter
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Variation In Levels Of Reproductive Hormones: High levels of ovarian steroid hormones in menstrual cycles are crucial for successful pregnancy (Lipson and Ellison,1996; Venners et al., 2006) and, as such, are important determinants of female reproductive success and evolutionary fitness. However, there are substantial differences in mean levels of estradiol and progesterone between populations, among women within a single population, and among menstrual cycles of a single woman (Figure 19.1) (Ellison et al., 1993; Jasienska and Jasienski, 2008). For example, urban women in the United States have progesterone levels that are on average 65% higher than those of women from the Democratic Republic of Congo (Ellison et al., 1993). In a rural population from Poland, as much as 46% of the among-cycle variation in salivary progesterone is due to differences among individual women, while the remaining 54% of variation is due to differences among cycles of individual women (Jasienska and Jasienski, 2008). Such high intercycle variation is probably caused by a seasonality of agricultural workload and is much higher than in nonseasonal, industrial populations. However, even in urban women from the United States and the United Kingdom, where lifestyle is less influenced by seasons, progesterone levels vary from cycle to cycle (Lenton et al., 1983; Sukalich et al., 1994; Gann et al., 2001). The present chapter reviews recent findings about variation in human female ovarian function, and more specifically, the levels of two primary female reproductive hormones: 17-B estradiol and progesterone.
... [5]). Negative67891011, positive121314151617 , U- shaped181920, and mixed or insignificant21222324252627 relationships between completed family size and lifespan have all been found. Some results have been criticized on statistical grounds; some authors doubt that the tradeoff exists at all (e.g.2829303132). ...
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Is there a trade-off between children ever born (CEB) and post-reproductive lifespan in humans? Here, we report a comprehensive analysis of reproductive trade-offs in the Framingham Heart Study (FHS) dataset using phenotypic and genotypic correlations and a genome-wide association study (GWAS) to look for single-nucleotide polymorphisms (SNPs) that are related to the association between CEB and lifespan. We calculated the phenotypic and genetic correlations of lifespan with CEB for men and women in the Framingham dataset, and then performed a GWAS to search for SNPs that might affect the relationship between post-reproductive lifespan and CEB. We found significant negative phenotypic correlations between CEB and lifespan in both women (rP = -0.133, P < 0.001) and men (rP = -0. 079, P = 0.036). The genetic correlation was large, highly significant and strongly negative in women (rG = -0.877, P = 0.009) in a model without covariates, but not in men (P = 0.777). The GWAS identified five SNPs associated with the relationship between CEB and post-reproductive lifespan in women; some are near genes that have been linked to cancer. None were identified in men. We identified several SNPs for which the relationship between CEB and post-reproductive lifespan differs by genotype in women in the FHS who were born between 1889 and 1958. That result was not robust to changes in the sample. Further studies on larger samples are needed to validate the antagonistic pleiotropy of these genes.
... In their baseline regression, there was only weak evidence for a negative correlation between number of sons and maternal longevity, although the association did become statistically significant when the sample was restricted to women born before 1815 married to 'ordinary labourers'. Furthermore, no evidence for differential effects on longevity by the sex of offspring was found by Jasienska et al. (2006) in a study of mothers in rural Poland. Similarly, Hurt et al. (2006) failed to find any association between the number of sons and maternal mortality in a sample from modern-day Bangladesh. ...
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Recent years have witnessed the emergence of a literature examining the effects of giving birth to sons on postmenopausal longevity in pre-industrial mothers. The original paper in this lineage used a sample (n=375) of Sami mothers from northern Finland and found that, relative to daughters, giving birth to sons substantially reduced maternal longevity. We examine this hypothesis using a similar and a much larger sample (n=930) of pre-industrial Sami women from northern Sweden, who in terms of their demographic, sociocultural and biological conditions, closely resemble the original study population. In contrast to the previously reported results for the Sami, we find no evidence of a negative effect of sons on maternal longevity. Thus, we provide the most compelling evidence to date that the leading result in the literature must be approached with scepticism.
... Maternal depletion syndrome is defined as deterioration of maternal condition occurring in women with high lifetime costs of reproduction, especially when they live in energy poor environment (Jasienska, 2013). High lifetime costs of reproduction may have long-term negative health consequences for the mother, such as increased risk of coronary heart disease (Lawlor et al., 2003) or diabetes (Simmons et al., 2006), and consequently result in reduced lifespan (Jasienska et al., 2006). We hypothesized that interaction between parity and birth spacing may be associated with the risk of low birth weight. ...
Article
Short interpregnancy intervals (IPI) and high parity may be synergistically associated with the risk of unfavorable pregnancy outcomes. This study tests if the effect of short IPI on the odds ratio for low birth weight (LBW, <2,500 g) differs across parity status. The study was carried out on the birth registry sample of almost 40,000 singleton, live-born infants who were delivered between the years 1995 and 2009 to multiparous mothers whose residence at the time of infant's birth was the city of Krakow. Multiple logistic regression analyses were used for testing the effect of IPI on the odds ratio (OR) for LBW, after controlling for employment, educational and marital status, parity, sex of the child, maternal and gestational age. Stratified analyses (according to parity) and tests for interaction were performed. Very short IPI (0-5 months) was associated with an increased OR for LBW, but only among high parity mothers with three or more births (OR = 2.64; 95% CI 1.45-4.80). The test for interaction between very short IPI and parity on the OR for LBW was statistically significant after adjustment for multiple comparisons (P = 0.04). Among low parity mothers (two births) no statistically significant associations were found between IPI and LBW after standardization. Parity may modify the association between short birth spacing and LBW. Women with very short IPI and high parity may have a higher risk of having LBW infants than those with very short IPI but low parity. Am. J. Hum. Biol., 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
... Women with symmetrical breasts were shown to have a higher number of offspring (Moller et al., 1995) and earlier age at first birth . Both the higher number of children and lower age at first birth may be caused indirectly by the increased attractiveness of symmetrical women, and not by their biological condition (Jasienska et al., 2006). In this study, we attempted to analyze a direct relationship between breast morphology and women's ability to invest in a fetus depending on its sex, yet we found no correlation. ...
Article
Objectives Breast size and fluctuating asymmetry (FA) are related to women's biological condition, as size correlates positively with fecundity, whereas FA correlates negatively with biological quality. We tested if breast volume, FA, and their changes during pregnancy are related to a fetus's sex. Women with bigger, symmetrical breasts, with a greater increase in size during pregnancy, should be more likely to carry a more ecologically sensitive and energetically demanding male fetus.Methods Ninety-three women participated in a 3-stage longitudinal study. 3D breast scans were performed in the first, second, and third trimester of pregnancy. As there was a small variation in pregnancy week at each research stage between the participants, the expected breast volume and FA values for the 12th, 22nd, and 32nd pregnancy week were calculated, basing on the obtained measurements. Those values were compared between mothers who carried a boy and mothers who carried a girl.ResultsAlthough women who carried a boy had somewhat larger breasts at each trimester than women who carried a girl, the difference was not significant. ANOVA for repeated measurements revealed a greater breast size increase in women carrying a boy (P = 0.039). FA decreased during pregnancy, but was not related to a fetus's sex.Conclusion Pregnancy-induced breast volume increase is a better cue of a fetus's sex than breast asymmetry or breast size per se, i.e., the traits that are supposed to indicate a woman's biological condition. Women with a larger increase in breast size during pregnancy are more likely to carry to term a more ecologically vulnerable male fetus. Am. J. Hum. Biol., 2015. © 2015 Wiley Periodicals, Inc.
... It is worth mentioning that other studies have associated longevity in the post-reproductive period with the number of children, however, the results are questionable and diverting (Doblhammer & Oeppen, 2003). While some reinforce the negative connection showing that reproductive costs reduce women longevity, others didn't find a connection or reached an opposite conclusion (Müller, Chiou, Carey, & Wang, 2002;Westendorp & Kirkwood, 1998;Smith, Mineau, & Bean, 2003;Korpelainen, 2000;Lycett;Dunbar, & Voland, 2000;Jasienska, Nenko, & Jasienski, 2006). ...
... For instance, women who did not have any additional help likely spent more time and energy providing for each additional child. Also, simply adding up the number of children to estimate the energetic and metabolic costs may not be an adequate measure since, for instance, it could be more physiologically demanding to bear and raise boys than girls [69]. Furthermore, parenting style may also influence the degree to which mothers perceive their children as burdensome, dependent on different stages in the life cycle or simply expectations for how children should behave and what mothers are supposed to do for their children; for instance, mothers with more traditional values are more likely to exhibit more frequent conflict with their children which is a major source of parenting stress and may thus contribute to poorer health [70]. ...
Article
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In this paper, we examine whether variation in reproductive investment affects the health of Roma women using a dataset collected through original anthropological fieldwork among Roma women in Serbia. Data were collected in 2014-2016 in several Roma semi-urban settlements in central Serbia. The sample consisted of 468 Roma women, averaging 44 years of age. We collected demographic data (age, school levels, socioeconomic status), risk behaviors (smoking and alcohol consumption), marital status, and reproductive history variables (the timing of reproduction, the intensity of reproduction, reproductive effort and investment after birth), in addition to self-reported health, height, and weight. Data analyses showed that somatic, short-term costs of reproduction were revealed in this population, while evolutionary, long-term costs were unobservable—contrariwise, Roma women in poor health contributed more to the gene pool of the next generation than their healthy counterparts. Our findings appear to be consistent with simple trade-off models that suggest inverse relationships between reproductive effort and health. Thus, personal sacrifice—poor health as an outcome—seems crucial for greater reproductive success.
... The disposable soma theory [7] emphasizes energetic and metabolic costs associated with reproduction. This cost of fertility could consist of maternal depletion: bearing and raising a large number of children is physically demanding and may have deteriorating effects on a woman's health and life span [8][9][10]. Maternal depletion may be especially important if a woman becomes widowed while she has to care for her young children [11]. ...
Article
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Several hypotheses have been put forward to explain the relationship between women’s fertility and their post-reproductive longevity. In this study, we focus on the disposable soma theory, which posits that a negative relationship between women’s fertility and longevity can be understood as an evolutionary trade-off between reproduction and survival. We examine the relationship between fertility and longevity during the epidemiological transition in the Netherlands. This period of rapid decline in mortality from infectious diseases offers a good opportunity to study the relationship between fertility and longevity, using registry data from 6,359 women born in The Netherlands between 1850 and 1910. We hypothesize that an initially negative relationship between women’s fertility and their longevity gradually turns less negative during the epidemiological transition, because of decreasing costs of higher parities. An initially inversed U-shaped association between fertility and longevity changes to zero during the epidemiological transition. This does suggest a diminishing environmental pressure on fertility. However, we find no evidence of an initial linear trade-off between fertility and post-reproductive survival.
... Some authors maintain that sons induce a higher physiological cost than daughters due to their greater corporal mass and higher metabolism (Helle et al., 2002). Whether reproductive costs reduce longevity in women is still a question for debate (Lycett et al., 2000; Jasié nska et al., 2006; Le Bourg, 2007; Gagnon et al., 2009). The cost of reproduction, mainly in women, may be not only physiological. ...
... Some studies have shown a negative correlation between NOC and life span because of the high energy expenditure during the pregnancy and lactation (8)(9)(10)(11)(12)(13). Moreover, childbearing requires a lot of physical and mental resources, with detrimental effects on female health and longevity (29)(30)(31)(32)(33). Other studies have found no significant correlation between NOC and life span (16,17). ...
Article
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Background Despite research efforts in this field for more than a century, the relationship between female fertility and longevity is unclear. This study was designed to investigate this relationship in Chinese oldest-old population. Methods The China Hainan Centenarian Cohort Study was performed in 18 cities and counties of Hainan. A total of 1,226 females, including 758 centenarian women and 468 women aged 80–99 years, were enrolled in this study. Using a standardized protocol, in-person interviews and blood analyses were conducted by a well-trained research team through home visits. Results Centenarian women had significantly lower number of children (NOC) and higher initial childbearing age (ICA) and last childbearing age (LCA) than women aged 80–99 years (p < 0.05 for all). Multivariate logistic regression analysis showed that NOC and testosterone (T) levels were positively associated with women aged 80–99 years, when centenarian women was considered as reference (p < 0.05 for all). ICA, LCA, and estradiol (E2) levels were negatively associated with women aged 80–99 years, when centenarian women was considered as reference (p < 0.05 for all). Conclusions The centenarians had crucial characteristics of less and delayed childbearing, indicating a negative relationship between female fertility and longevity in Chinese oldest-old population. Serum E2 levels were positively associated and serum T levels were negatively associated with longevity. The less and late childbearing might be a significant factor of longevity, and successful aging might be promoted by reducing and delaying female childbearing.
... 2009; Jasienska, Nenko, & Jasienski, 2006). Poor health in women with high parity may result from long-term changes in immune system (Marttila et al., 2015) and higher levels of oxidative stress (Ziomkiewicz et al., 2016)-a main factor contributing to body's deterioration with progressing age (Finkel & Holbrook, 2000). ...
Article
Objectives: The costs associated with reproduction (i.e., gestation, lactation, childcare) have long-term negative consequences by elevating risk of disease and reducing lifespan. We tested the hypotheses that high parity, and thus high reproductive costs bear by women, is perceived by other people when they evaluate facial appearance of health, attractiveness and age of mothers. Materials and methods: Using computer software we created average facial images based on real photographs of post-menopausal women with varying number of children; 3 parity categories were created (1-2, 4-5, and 7-9 children). Study participants (N = 571) were asked to choose the face they perceived as more attractive, younger and healthier via two-alternative forced choice questions asked in three randomized blocks. Results: Women who had given birth to fewer children were judged both by men and women as more attractive, younger and healthier than women with more children. In each category the lowest scores were received by women from highest parity category (7-9 children). Discussion: Mechanisms behind the observed variation in facial appearance are not known but higher levels of oxidative stress among women with high parity may explain their faster aging and lower attractiveness in older age. These results suggest that costs of reproduction might affect women's physical appearance.
... Similarly, research from rural Poland found that a higher number of daughters increased fathers' life span. This same study found that greater numbers of children (of either sex) reduce maternal longevity (Jasienska, Nenko, & Jasienski, 2006). A study from rural Bangladesh found no effect of number of daughters on either maternal or paternal mortality, but greater number of sons increased mortality for parents (Hurt et al., 2006). ...
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Objective: To examine whether older parents in China would benefit more from daughters' care than from sons' emotional care. Method: Analysis of the unique data sets of the Chinese Longitudinal Healthy Longevity Survey conducted in 2002, 2005, and 2008-2009 in 22 provinces. Results: As compared with having son(s), having daughter(s) is significantly more beneficial at older ages in China, with regard to maintaining higher cognitive capacity and reducing mortality risk. Such daughter advantages in providing emotional care to older parents are more profound among the oldest-old aged 80+ as compared with the young-old aged 65 to 79 and surprisingly more profound in rural areas as compared with urban areas, even though son preference is much more common among rural residents. Discussion: We describe how educational campaigns aimed at informing the public about the benefits of daughter(s) for older parents' health outcome could help promote gender equality and reduce traditional son preference, especially in rural China.
Article
Objective of this study was to assess the risk of coronary heart disease (CHD) associated with the combination of employment status and child care among women of working age, also examining the sex of the offspring. Only two previous studies investigated the effect of double burden on CHD, observing an increased risk among employed women with high domestic burden or providing child care, although the relative risks were marginally or not significant. The study population was composed of all women 25-50 years old at 2001 census, living in Turin in families composed only by individuals or couples, with or without children (N = 109,358). Subjects were followed up during 2002-2010 for CHD incidence and mortality through record-linkage of the cohort with the local archives of mortality and hospital admissions. CHD risk was estimated by multivariate Poisson regression models. Among employed women, CHD risk increased significantly by 29% for each child in the household (IRR = 1.29) and by 39% for each son (IRR = 1.39), whereas no association with the presence of children was found among non-employed women or among employed women with daughters. When categorized, the presence of two or more sons significantly increased CHD risk among employed women (IRR = 2.23), compared to those without children. The study found a significant increase in CHD risk associated with the presence of two or more sons in the household, but not daughters, among employed women. This is a new finding, which should be confirmed in other studies, conducted also in countries where the division of domestic duties between males and females is more balanced, such as the European Nordic countries. Copyright © 2015 Elsevier Ltd. All rights reserved.
Article
According to the disposable soma theory, a cost for reproduction could exist in human beings and other species and, thus, longevity could decrease when women have a higher number of children. The purpose of this article is to review the evidence in populations living or not living under natural fertility conditions, i.e. when fertility is near its biological maximum. The results indicate that in natural fertility conditions longevity does not decrease when the number of children increases but, in modern populations, mortality could slightly increase when women have more than ca 5 children. Complete data for these modern cohorts will tell us, one day, whether these results are still observed when the variable of interest is longevity and not only mortality.
Article
Objectives Oxidative stress is hypothesized to contribute to age‐related somatic deterioration. Both reproductive and ecological context may necessitate tradeoffs that influence this outcome. We examined whether measures of lifetime reproductive effort were related to levels of oxidative stress biomarkers in peri‐ and post‐menopausal women and whether associations were moderated by rural or urban residence. Methods We surveyed 263 healthy women (age 62.1 ± 10.0 SD) from rural (N = 161) and urban Poland (N = 102), collecting sociodemographic data and urine samples to analyze biomarkers of oxidative stress (8‐oxo‐2′‐deoxyguanosine, 8‐OHdG) and antioxidative defense (copper‐zinc superoxide dismutase, Cu‐Zn SOD). Linear regression models, adjusted for residence, were used to test for associations between reproductive effort and 8‐OHdG and Cu‐Zn SOD. Results Univariate models demonstrated significant associations between gravidity and the biomarkers of oxidative stress (8‐OHdG: R² = 0.042, P ≤ .001; Cu‐Zn SOD: R² = 0.123, P ≤ .001). Multivariate models incorporating potential confounding variables, as well as cross‐product interaction terms, indicated that gravidity was associated with 8‐OHdG (P < .01, R²adj = 0.067) and Cu‐Zn SOD (P = .01, R²adj = 0.159). Residence (ie, urban vs rural) did not significantly moderate the associations between the biomarkers and reproductive effort. Conclusions Higher lifetime reproductive effort contributes to increases in oxidative stress and antioxidative defenses. Our results provide evidence of potential mechanisms underlying the physiological tradeoffs influencing senescence for women with high reproductive effort. We illustrate the value of applying an evolutionary perspective to elucidate variation in human health and senescence.
Chapter
Mario Bunge calls his ethical system agathonism, to signify “seeking the good”. For Bunge the good is above all else the satisfaction of human needs. In this way, human needs act as the foundation stone of Bunge’s ethical system. The aim of this chapter is to reset the foundation stone of agathonism, while allowing the valuable portions of the edifice to remain. Space limitations leave fulfilment of the latter as an exercise for the reader. Consequently, this chapter is mostly of a critical nature. New characterizations of rights, moral duties, and the relation between rights and duties are proposed.
Article
The important role of GH in the control of mammalian longevity was first deduced from extended longevity of mice with genetic GH-deficiency (GHD) or GH-resistance. Mice with isolated GHD (IGHD) due to GHRH or GHRH-R mutations, combined deficiency of GH, PRL, and TSH, or global deletion of GH receptors live longer than their normal siblings. They also exhibit multiple features of delayed and/or slower aging, accompanied by extension of healthspan. The unexpected, remarkable longevity benefit of severe endocrine defects in these animals presumably represents evolutionarily conserved trade-offs among aging, growth, maturation, fecundity, and the underlying anabolic processes. Importantly, the negative association of GH signaling with longevity extends to other mammalian species, apparently including humans. Data obtained in humans with IGHD type 1B, due to a mutation of the GHRHR gene, in the Itabaianinha County, Brazil, provide unique opportunity to study the impact of severe reduction in GH signaling on age-related characteristics, health, and functionality. Individuals with IGHD are characterized by proportional short stature, doll facies, high-pitched voices, and central obesity. They have delayed puberty, but are fertile and generally healthy. Moreover, these IGHD individuals are partially protected from cancer and some of the common effects of aging and can attain extreme longevity, 103 years in one case. We believe that low, but detectable, residual GH secretion combined with life-long reduction of circulating IGF-1 and with some tissue levels of IGF-1 and/or IGF-2 preserved, may account for the normal longevity and apparent extension of healthspan in these individuals.
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Although genetic factors are known to influence the human aging process, the proportion of life span and longevity variation explained by them is still controversial. We evaluated the genetic contribution to life span using historical data from three Alpine communities in South Tyrol, Italy. We estimated the heritability of life span and survival to old age (longevity), and we assessed the hypothesis of a common genetic background between life span and reproduction. The heritability of life span was 0.15 (SE = 0.02), whereas the heritability of longevity increased from 0.20 to 0.35 as the longevity threshold increased. Heritability estimates were little influenced by shared environment, most likely due to the homogeneity of lifestyle and environmental factors in our study population. Life span showed both positive association and genetic correlation with reproductive history factors. Our study demonstrates a general low inheritance of human life span, but which increases substantially when considering long-living individuals, and a common genetic background of life span and reproduction, in agreement with evolutionary theories of aging.
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Objectives: Life history theory predicts a trade-off between female investment in reproduction and somatic maintenance, which can result in accelerated senescence. Oxidative stress has been shown to be a causal physiological mechanism for accelerated aging and a possible contributor to this trade-off. We aimed to test the hypothesis for the existence of significant associations between measures of reproductive effort and the level of oxidative stress biomarkers in premenopausal and postmenopausal American women. Methods: Serum samples and questionnaire data were collected from 63 premenopausal and postmenopausal women (mean age 53.4 years), controls in the Connecticut Thyroid Health Study, between May 2010 and December 2013. Samples were analyzed for levels of 8-OHdG and Cu/Zn-SOD using immunoassay method. Results: Levels of oxidative damage (8-OHdG) but not oxidative defense (Cu/Zn-SOD) were negatively associated with parity and number of sons in premenopausal women (r = -0.52 for parity, r = -0.52 for number of sons, P < .01). Together, measures of reproductive effort, women's BMI, age, and menopausal status explained around 15% of variance in level of 8-OHdG. No association between reproductive effort characteristics and oxidative damage was found for postmenopausal women. Conclusions: We found no evidence of a trade-off between somatic maintenance as measured by 8-OHdG and reproductive effort in women from this American population. On the contrary, higher gravidity and parity in premenopausal women was associated with lower damage to cellular DNA caused by oxidative stress. These results highlight the importance of population variation and environmental conditions when testing the occurrence of life-history trade-offs.
Article
Although sons are thought to impose greater physiological costs on mothers than daughters, sons may be advantageous for parental survival in some social contexts. The authors examined the relationship between the sex composition of offspring and parental survival in contemporary China and Taiwan. Because of the importance of sons for the provision of support to elderly parents in these populations, the authors hypothesised that sons would have a beneficial effect on parental survival relative to daughters. The authors used data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) and the Taiwan Longitudinal Study of Aging (TLSA). The CLHLS sample consisted of 4132 individuals aged 65 years and over in 2002. The TLSA sample comprised two cohorts: 3409 persons aged 60 years and over in 1989 and 2193 persons aged 50-66 years in 1996. These cohorts were followed up for 3, 18 and 11 years, respectively. The Cox proportional hazards model was used to estimate the relationship between the sex composition of offspring and parental mortality. Based on seven measures of sex composition, no protective effect of sons was found in either China or Taiwan. For example, in the 1989 Taiwan sample, the hazard ratio (HR) for maternal mortality associated with having an eldest son was 0.979 (95% CI 0.863 to 1.111). In Taiwan, daughters may have been more beneficial than sons in reducing mortality in recent years. The authors offer several explanations for these findings, including possible benefits associated with emotional and interpersonal forms of support provided by daughters and negative impacts of conflicts arising between parents and resident daughters-in-law.
Article
According to life history theory, increased investment in reproductive function (physiology and behaviour) at different times throughout the life course affects the risk of many diseases and, ultimately, longevity. Although genetic factors contribute to interindividual and interpopulation variation in reproductive traits, the dominant source of variability is phenotypic plasticity during development and adult life. Reproductive traits in both sexes evolved sensitivity to ecological conditions, as reflected in contemporary associations of hormone concentrations with geographical setting, nutritional status, and physical activity level. Lifetime exposure to increased concentrations of sex hormones is associated with the risk of some cancers, hence decreasing fertility patterns contribute to secular increases in their incidence. Conversely, increased investment in reproductive function might compromise somatic investment in health, such that faster sexual maturation and higher parity increases risk of diabetes and cardiovascular disease. An evolutionary perspective on reproductive biology could improve the efficacy of public health efforts to reduce the risk of hormone-sensitive cancers and other non-communicable diseases.
Article
Objectives: Women should differ in their reproductive strategies according to their nutritional status. We tested a hypothesis that women who have a good nutritional status early in life, as indicated by a shorter waiting time to the first birth (first birth interval, FBI), are able to afford higher costs of reproduction than women who have worse nutritional condition. Methods: We collected data on 377 women who got married between the years 1782 and 1882 in a natural fertility population in rural Poland. The study group was divided into tertiles based on the length of FBI. Results: Women with the shortest FBI had a higher number of children (P = 0.005), higher number of sons (P = 0.01), and shorter mean interbirth intervals (P = 0.06). Women who had ever given birth to twins had shorter FBI than women of singletons (20.1 and 26.1 months, respectively; P = 0.049). Furthermore, women with a shorter FBI, despite having higher costs of reproduction, did not have a different lifespan than women with a longer FBI. Conclusions: Our results suggest that women who were in better energetic condition (shorter length of FBI), achieved higher reproductive success without reduction in lifespan. FBI reflects interindividual variation, which may result from variation in nutritional status early in life and thus may be a good predictor of subsequent reproductive strategy. We propose to use FBI as an indicator of women's nutritional status in studies of historical populations, especially when information about social status is not available.
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This chapter presents new research directions and hypotheses based on the evolutionary relationships between reproductive effort and contemporary health challenges in men. Drawing on life history, these hypotheses are grounded in the observation that human male reproductive strategies exhibit a much broader range of variability compared to other great apes. Specifically, human males are unique in that they exhibit the capacity to devote a significant amount of time and energy to offspring and mate care, often spending much more of their lives providing paternal investment compared to other primates and indeed many mammals. Men also exhibit the capability to negotiate and partition investment in offspring according to perceived paternity. The extraordinary range of human male reproductive options can be viewed as selection for neuroendocrine adjustments in response to shifting mortality challenges and extended life spans. We hypothesize that (1) investment in offspring and mates evolved in tandem with decreases in human male mortality and morbidity, (2) male fertility at older ages coevolved with an increased capacity to defend against degenerative diseases, (3) testosterone and other neuroendocrine mechanisms are primary targets of selection for the evolution of these traits, and (4) trade-offs between male health maintenance, variation in paternal investment, and male reproductive strategies are contingent on energetic constraints. Drawing on research from the literature, we provide a number of case studies that inform our hypotheses and provide guidance for future research.
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Reproduction in females is costly: pregnancy, breast-feeding, and childcare require energy, and thus energetic costs are indispensable feature of reproduction. Pregnancy and lactation also require many physiological changes, including in maternal immune system and increased levels of oxidative stress. Finally, genes involved in encoding traits related to reproduction often have multiple functions. Some of these genes have alleles that support reproduction but also increase risk of diseases later in life, and their carriers have higher mortality. Results of studies testing relationships between reproduction and health and reproduction and life span are contradictory, possibly due to methodological problems and theoretical framework problems. There is a need for studies that would analyze these relationships at both genetic and phenotypic levels, and that would comprehensively calculate costs of reproductive investment, including not only number of children but also birth spacing, lactation, childcare, and extended reproductive effort.
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Preference for a son is common in the world. Was this preference prevalent in ancient cultures? Is this the preference described in the Bible? If so, who was the character who preferred specifically son? Is this trend continuing in contemporary times? Are there any consequences of this preference on the human population? Is sex selection prevalent in order to eliminate female fetuses? This research deals with the biblical verse that describes a preference for sons in a woman, evaluating this issue from a contemporary perspective. Studying the available literature on sex selection, either ancient or contemporary, may shed light on this issue and provide tools for better management of sex selection of children in modern times.
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Few studies have so far enquired into the relationship between being a grandparent and health and mortality outcomes, and the majority of these have looked exclusively at grandparents who take over parenting responsibility for their grandchildren. This study aims to fill this gap in the knowledge of how family structure is linked to mortality by focusing on whether being a grandparent in itself is associated with mortality. Norwegian parents in the age groups 40–73 are analysed using register data that encompass the entire population. The analysis is based on discrete-time hazard models, estimated for the years 1980–2008. I find a mortality disadvantage of being a grandfather, which is particularly strong for those who become grandfathers at an early age. Controlling for characteristics of the middle generation such as sex, education and marital status does not remove the association. For men the mortality disadvantage is not influenced by the number of grandchildren or the number of sets of grandchildren. For women there is significantly higher mortality only for those who become grandmothers in their thirties or forties, who are married or who have many children. Becoming a grandmother after age 50 is associated with significantly lower mortality. At least part of these associations are likely due to selection effects, however they may also to some extent be caused by the individuals' relationship with grandchildren, and children who have become parents themselves.
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Helle et al. (2000. Sons reduced maternal longevity in preindustrial humans. Science, 296, 1085) argued that giving birth to sons reduced maternal longevity in pre-industrial societies due to higher physiological costs of bearing sons and the elevated testosterone levels observed in mothers carrying male foetuses. The present study examined this hypothesis using a more comprehensive dataset and evaluated the merits of the statistical approach used in previous studies to identify the cost of giving birth to sons in terms of maternal old-age longevity. The analysis in Helle et al. (2002. Sons reduced maternal longevity in preindustrial humans. Science 296, 1085) was extended by using a considerably larger dataset of pre-industrial Swedish women, and with careful consideration paid to methodological problems of sample selection and omitted variable bias. We argue that the previous literature has underestimated the difficulties in quantifying the trade-off between parity and longevity due to unobserved heterogeneity in health. However, under less restrictive assumptions, one can estimate the marginal impact of a son for a fixed family size. No evidence was found of a negative relative impact of sons. Neither was any evidence found in favour of the male-biased intra-household resource competition hypothesis proposed elsewhere in the literature, despite the poverty of the study population. These results are robust to a wide range of specifications tested. The failure to reproduce earlier findings and the fact that studies in this area of research seem to continue to yield conflicting results warrant much caution in discussing and evaluating results. It is likely that the negative effect of sons, if it existed, only manifested itself under conditions that are not yet fully understood. We also argue that the previous literature on this topic has not fully acknowledged the inference problems associated with omitted variable bias and sample selection.
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It has been argued that the priority that natural selection places on reproduction negatively affects other processes such as longevity and the problem posed by this trade-off underlies the disposable soma theory for the evolution of human ageing. Here we examine the relationship between reproduction and longevity in a historical human population (the Krummhörn, north-west Germany 1720-1870). In our initial analyses, we found no support for the hypothesized negative effects of reproduction on longevity: married women who remained childless lived no longer than women who reproduced and women who had few children lived no longer than women who had many children. However, more detailed analyses in relation to socio-economic class revealed that the extent to which reproduction has an effect on longevity is a function of the level of economic deprivation. We found that, when possible sources of confound were controlled for (e.g. duration of marriage and amount of time spent in fecund marriage), there is an increasingly strong relationship between longevity and reproduction with increasing poverty.
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The relation between fertility and postmenopausal longevity is investigated for a sample of 1635 women from a historical (17th to 18th century) French-Canadian cohort who lived past the age of 50 years. We find that increased fertility is linked to increased rather than decreased postreproductive survival. Postreproductive life expectancy extension is found to be tied to late births. This finding sheds new light on the cost of reproduction and may be viewed as supporting a new paradigm that states that reproductive potential drives remaining longevity. The emerging reproductive potential concept complements the well-established cost of reproduction hypothesis. Alternative explanations for the observed association are also explored. A specific finding is that the degree to which mortality increases for 50-year-old mothers as a result of senescence is closely tied to the logarithm of the age of their youngest child. For example, 50-year-old mothers experience a mortality decrease of 38% and an increase of remaining lifetime of 3.93 years for every 10-fold decrease in the age of their youngest child. This amount of gain in remaining life expectancy would apply to a mother with a two-year-old child as compared with a mother with a 20-year-old offspring. We also find evidence for the existence of vulnerable periods in human life history that are characterized by phases of heightened mortality and are found to be tied to reproduction and senescence.
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Helle et al .( 1) showed that producing and raising sons reduced the longevity of pre- industrial Sami women, whereas daughters tended to have the opposite effect. They suggested that the life-shortening effect of sons could be attributed to higher endocri- nological or physiological costs of produc- ing sons compared with those of producing daughters, and that the life-elongating ef- fect of raising daughters might be the out- come of daughters helping in the household of their mothers. To examine the validity of those ideas, we explored the costs of pro- ducing sons rather than daughters in the two premodern populations of Krummhorn (Ostfriesland, Germany, 1720 to 1874) and St. Lawrence valley (Quebec, Canada, 1608 to 1760), applying the same data selection criteria and linear regression model as Helle et al .( 2). For the Krummhorn population, we found the same negative relationship be- tween the number of sons born and the age of the mother at death, although this result was not statistically significant. There was also a very slight and likewise not signifi- cant positive correlation concerning the number of daughters born (sons: - 0.180 0.200, t - 0.900, P 0.368; daughters: 0.049 0.209, t 0.234, P 0.815) (Fig. 1, A and B). In the Quebec population, we found a positive relation- ship between the number of sons or daugh- ters born and maternal age, but only the latter relationship is significant (sons: 0.081 0.092, t 0.881, P 0.378;
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Whether a cost of reproduction exists among humans is still questionable. A major study of aristocratic British families finds a significant positive correlation between parity and late-life mortality, which indicates a trade-off between reproduction and longevity. This result is supported by four other studies, while earlier studies have not found a relationship or came to the opposite conclusion. We show that in natural fertility populations the relationship between fertility and late-life mortality cannot be studied correctly without considering the effects of differences in health and of mortality selection during childbearing ages because these two effects lead to a dampening of the true relationship. If these effects are controlled in Hollingsworth's genealogy of the British peerage a significant trade-off between reproduction and longevity exists for females but not for males.
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In humans, there is evidence that the physiological cost to the mother of bearing sons is greater than of bearing daughters. Parents should manipulate the sex of offspring born in response to resource availability to maximize their reproductive success. Here, we demonstrate that, within a rural food-stressed community in southern Ethiopia, there is a strong association between the sex of the most recent birth and maternal nutritional status, measured either by body mass index or mid-upper arm muscle area (AMA) (measures of fat and muscle mass). The effect of muscle mass is very marked: those women in the upper 25th percentile of AMA were more than twice as likely to have had a recent male birth than those in the lowest 25th percentile.
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Due to their effect on maternal testosterone levels, sons are said to have reduced maternal longevity in pre-industrial humans. This analysis, using information from a Flemish agricultural village in the 18th-20th centuries, confirms the presence of a negative effect of sons on maternal longevity. However, the effect is mainly observed for mothers belonging to the least privileged social group and for sons surviving their fifth birthday. Both findings make the above-mentioned biological explanation relative. However, a plausible alternative, social interpretation is male-dominated intra-household resource competition. It is reasonable to assume that only sons above a certain age are able to claim a serious amount of resources and that competition is strongest within the least privileged social group.
Article
In order to study the hormonal correlates of the tradeoff between mating and parenting effort in human males, we examined the salivary testosterone (T) levels of 58 Boston-area men who were either unmarried (n=29), married without children (n=14), or married with children (n=15). Additionally, we asked participants to complete a questionnaire that surveyed their demographic, marital, and parenting backgrounds. We tested the hypotheses that (1) T levels will be lower in married than in unmarried men and (2) married men with children will have lower T levels than unmarried men and married men without children. We also tested a series of hypotheses relating variation in parenting and spousal relationships to T. We found that married men with and without children had significantly lower evening T than unmarried men. No significant differences in T were found among the groups in morning samples. Among married men without children, higher scores on a “spousal investment” measure and more hours spent with a man's wife on his last day off work were both associated with lower T levels. We suggest that lower T levels during the day among fathers may facilitate paternal care in humans by decreasing the likelihood that a father will engage in competitive and/or mating behavior.
Article
Members of the Turkana tribe include settled and nomadic peoples who reside in the southern part of Turkana District in the semiarid region of northwest Kenya. Nomadic Ngisonyoka Turkana keep livestock (camels, cattle, sheep, goats, donkeys), subsist principally on livestock products, and move camps frequently in search of forage for the livestock; settled Turkana cultivate foods along the principal rivers. Both nomadic and settled Turkana are subject to limited food resources on seasonal and long-term bases. Protein from meat, blood, and milk is sufficient in the diet, but food energy is limited, as are body fat reserves. Previous work has documented a decline in maternal adiposity with age in a large sample of the relatively lean nomadic women, and a negative association of fat stores with parity in a smaller sample of nomadic women. The problem of maternal depletion of fat energy reserves as a function of female reproductive history is explored in this study through anthropometry in a relatively large sample (N = 312) of nomadic and settled women. Both nomadic and settled women displayed some parity-related losses in fat stores. The relationship was stronger in the nomads, even after controlling for age. © 1992 Wiley-Liss, Inc.
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Evolutionary theory predicts that organisms make trade-offs between their somatic and reproductive energy budgets. Thus every round of reproduction should result in a concomitant decline in the parents' total energy reserves. Among humans this prediction was corroborated more than 25 years ago when fertility-related nutritional depletion was reported among mothers in the Highlands of New Guinea (Jelliffe and Maddocks, 1964). More recently, however, a number of studies of fertility and maternal nutritional status in both developed and developing nations have reported fertility-related increases in various indices of adiposity and lean body mass. Such findings have called the so-called "maternal depletion syndrome" into question, and have raised serious doubts as to whether the phenomenon is widely generalizable to all populations. In light of this recent controversy, data are presented here on fertility-related changes in maternal adiposity and lean body mass among the Au, a lowland forager-horticulturalist population in Papua New Guinea. While both a short-term decline in adiposity following childbirth, and a long-term fertility-related decline are seen among more traditional Au, individuals with a regular source of wage-income show only the former. There are no significant changes in lean body mass with increasing fertility in either group. The finding of significant socioeconomic variation in the capacity to withstand the stress of repeated reproduction even within this one extremely rural area of Papua New Guinea may lend insight into why previous studies have been unable to find evidence of maternal depletion. The fertility-related decline in adiposity that is reported for the more traditional Au is consistent with the predictions of evolutionary theory.
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Available standard intrauterine growth curves based on birthweights underestimate foetal growth in preterm period. New growth curves are presented based on data from four Scandinavian centres for 759 ultrasonically estimated foetal weights in 86 uncomplicated pregnancies. Mean weight of boys exceeded that of girls by 2-3%. A uniform SD value of 12% of the mean weight was adopted for the standard curves as the true SD varied non-systematically between 9.1 and 12.4%. Applied to an unselected population of 8663 singleton births, before 210 days of gestation, 32% of birthweights were classified as small-for-gestational age (SGA; i.e. below mean - 2 SD); the corresponding figures were 11.1% for gestational ages between 210 and 258 days, and 2.6% for ages of 259 days or longer. The new growth curves reveal better the true distribution of SGA foetuses and neonates, and are suggested for use in perinatological practice.
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The suppression of reproductive function is known to occur in women engaging in activities that require high energetic expenses, such as sport participation and subsistence work. It is still unclear, however, if reproductive suppression is a response to high levels of energy expenditure, or only to the resulting state of negative energy balance. To our knowledge, this study provides the first evidence that work-related energy expenditure alone, without associated negative energy balance, can lead to the suppression of reproductive function in women. We document suppression of ovarian function expressed as lowered salivary progesterone levels in women from an agricultural community who work hard, but remain in neutral energy balance. We propose two alternative evolutionary explanations (the 'pre-emptive ovarian suppression' hypothesis and the 'constrained down-regulation' hypothesis) for the observed results.
Article
Despite the longer gestation of girls, their birthweight is less than that of boys. Because unlike-sex twins provide a natural situation in which to investigate the influence of sex on gestation, we compared birthweight and gestation of 1929 same-sex and unlike-sex dizygotic pairs. Length of gestation in unlike-sex pairs was similar to that of female same-sex pairs, and significantly (0.4 weeks; p=0.02) longer than that of male same-sex pairs. Birthweight of girls from unlike-sex pairs was similar to that of girls from same-sex pairs, but boys from unlike-sex pairs weighed 78 g more than boys from same-sex pairs (p=0.001). These data show that in unlike-sex pairs it is the girl that prolongs gestation for her brother, resulting in a higher birthweight than that of same-sex boys.
Article
Female mammals can optimize their fitness by temporal suppression of reproductive function in response to unfavorable environmental conditions. Since reproduction is energetically demanding for a human female, ovarian function is expected to be sensitive to factors influencing energy availability and metabolism. Dieting and exercise in women from industrial countries, and low-calorie diet and workload in women from developing countries, are often associated with ovarian suppression. This study shows that in Polish rural women seasonal changes in workload correlate with seasonal changes in indices of ovarian function (progesterone measured in saliva samples collected daily for six menstrual cycles for each subject). Mean levels of energy expenditure of the most work demanding weeks of the summer exceeded mean levels of energy expenditure during winter by 37%. Energy intake in this population was sufficient throughout the year. During the summer, when physical work was most intense, low values of progesterone levels were observed (178.2 pmol/L in July and 182.2 pmol/L in August), indicating ovarian suppression. Mean progesterone levels rose to 234.6 pmol/L in October when levels of energy expenditure were lower due to cessation of harvest-related activities. As indicated by several causal models tested through path analysis, energy expenditure was the only variable responsible for suppressed progesterone levels during the summer. Variables describing the nutritional status and energy balance did not correlate significantly with progesterone levels; neither body weight nor body fat or seasonal changes of these variables seem to influence ovarian function in this population. Thus work-related energy expenditure does not need to lead to negative energy balance in order to cause suppression of reproductive function in women.