An evolutionary perspective on the association between grandmother-mother relationships and maternal mental health among a cohort of pregnant Latina women

Grandmothers are often critical helpers during a mother's reproductive career. Studies on the developmental origins of health and disease demonstrate how maternal psychological distress can negatively influence fetal development and birth outcomes, highlighting an area in which soon-to-be grandmothers (henceforth “grandmothers”) can invest to improve both mother and offspring well-being. Here, we examine if and how a pregnant woman's mental health– specifically, depression, state-anxiety, and pregnancy-related anxiety– is influenced by her relationship with her fetus' maternal and paternal grandmother, controlling for relationship characteristics with her fetus' father. In a cohort of pregnant Latina women in Southern California (N = 216), we assessed social support, geographic proximity, and communication between the fetus' grandmothers and pregnant mother. We assessed maternal mental health with validated questionnaire-based instruments. We find that both social support from and communication with the maternal grandmother were statistically associated with less depression, while no paternal grandmother relationship characteristics were statistically significant in association with any mental health variable. These results align with the idea that maternal grandmothers are more adaptively incentivized to invest in their daughters' well-being during pregnancy than paternal grandmothers are for their daughters-in-law. Results suggest that the positive association of maternal grandmothers with mothers' mental health may not hinge on geographic proximity, but rather, potentially function through emotional support. This work represents a novel perspective describing a psychological and prenatal grandmaternal effect.     

Will granny save me? Birth status,survival, and the role of grandmothers in historical Finland

Grandmothers play a crucial role in families enhancing grandchild wellbeing and survival but their effects can be context-dependent, and the children born in poor conditions are most likely to benefit from the investments made by helping grandmothers. In this study, we examined, for the first time, whether grandmothers' presence modified associations between adverse birth status and survival up to 5 years of age. In detail, we verified, whether (i) firstborns, (ii) twins, (iii) children born within 24 months after their sibling, and (iv) children followed by short interval (i.e. their younger sibling was born within 24 months) survived better when either their maternal, paternal, or both grandmothers were present. Moreover, we evaluated whether illegitimate children survived better when the maternal grandmother was present. We used an extensive and largely pre-industrial demographic dataset collected from parish population registers kept by the Lutheran Church of Finland from years 1730–1895. We show that although grandmother presence cannot mitigate adverse effects of many poorer birth conditions, grandchildren whose next sibling was born after a short interval survived better when the maternal grandmother was present. Taken together, these findings highlight an important role of grandmothers in compensating the mother's investment in the new baby, thus enabling overall faster successful reproductive rate of mothers. Whilst the opportunity for grandmothers to mitigate the risks of adverse birth statuses is limited, this study does show - through the beneficial effect on survival for those with a short subsequent birth interval - that grandmothers can increase their daughters' and their own reproductive success.     

Availability and adaptive value of reproductive and postreproductive Japanese macaque mothers and grandmothers

Prior tests of the grandmother hypothesis have suggested that postreproductive female Japanese macaques,Macaca fuscata , do not significantly improve the survivorship of their descendents. However, not all postreproductive females are grandmothers, and not all grandmothers are postreproductive. In this study we looked at the daughters and grandchildren of 70 female Japanese macaques to assess the availability and adaptive value of reproductive and postreproductive mothers and grandmothers. We found that postreproductive Japanese macaque grandmothers are very rare. Only 2.8% of the sample of daughters had a postreproductive grandmother available when they began to reproduce, and only 4.2% of the reproductive life span of the daughter (less than 6 months for the average female) was spent with a postreproductive grandmother available to help the daughter. Grandchildren who survived to age 5 had a postreproductive grandmother available to them for only 4% of the first 5 years of life (i.e. a couple of months on average). The presence of a living mother, irrespective of her reproductive status, was associated with improved reproduction in her adult daughters, and the presence of a postreproductive grandmother was associated with significantly improved survivorship of grandchildren to age 1. While improved maternal investment does not appear to be the primary explanation for reproductive termination in Japanese monkeys, the few postreproductive females that have unweaned grandchildren available appear to have a positive influence on their survival. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Old grandmothers provide essential care to their young granddaughters in a free-ranging group of Japanese monkeys (<Emphasis Type="Italic">Macaca fuscata</Emphasis>)

This study reports 2 cases in which old grandmothers without dependent offspring provided essential care to their young granddaughters in a free-ranging group of Japanese monkeys (Macaca fuscata). In the first case, a 24-year-old grandmother provided essential care for the survival of her 2-month-old granddaughter for at least 6 days during which the mother had temporarily disappeared from the group for reasons unknown. In the second case, a 14-month-old granddaughter began sucking from her 23-year-old grandmother within 6 weeks after her mother gave birth to a younger sibling. For at least 6 months, the grandmother exhibited various patterns of maternal behavior toward her granddaughter. The behavioral data obtained in this study indicated that old yet healthy females without dependent offspring could contribute to the survival of their young grandchildren.     

Grandma plays favourites: X-chromosome relatedness and sex-specific childhood mortality

Biologists use genetic relatedness between family members to explain the evolution of many behavioural and developmental traits in humans, including altruism, kin investment and longevity. Women''s post-menopausal longevity in particular is linked to genetic relatedness between family members. According to the ‘grandmother hypothesis’, post-menopausal women can increase their genetic contribution to future generations by increasing the survivorship of their grandchildren. While some demographic studies have found evidence for this, others have found little support for it. Here, we re-model the predictions of the grandmother hypothesis by examining the genetic relatedness between grandmothers and grandchildren. We use this new model to re-evaluate the grandmother effect in seven previously studied human populations. Boys and girls differ in the per cent of genes they share with maternal versus paternal grandmothers because of differences in X-chromosome inheritance. Here, we demonstrate a relationship between X-chromosome inheritance and grandchild mortality in the presence of a grandmother. With this sex-specific and X-chromosome approach to interpreting mortality rates, we provide a new perspective on the prevailing theory for the evolution of human female longevity. This approach yields more consistent support for the grandmother hypothesis, and has implications for the study of human evolution.     

Patterns of grandmaternal behaviour in free-ranging Hanuman langurs (Presbytis entellus)

The behaviour of two Hanuman langur grandmothers towards their grandchildren is examined with emphasis on the spatial relationship, the contact behaviour, and vigilance. Interaction patterns with infants and juveniles are analysed separately to disclose the influence of a social partner's reproductive value and the variance of this value on grandmaternal behaviour. The shape of grandmaternal behaviour seems to differ for male and female grandchildren, and it seems to depend on the reproductive value of both, the grandmother and the grandchild. These results are in accordance with sociobiological hypotheses. Evaluation of costs and benefits suggests that grandmaternal behaviour in langurs can be called investment.     

Increased longevity evolves from grandmothering

Postmenopausal longevity may have evolved in our lineage when ancestral grandmothers subsidized their daughters'' fertility by provisioning grandchildren, but the verbal hypothesis has lacked mathematical support until now. Here, we present a formal simulation in which life spans similar to those of modern chimpanzees lengthen into the modern human range as a consequence of grandmother effects. Greater longevity raises the chance of living through the fertile years but is opposed by costs that differ for the sexes. Our grandmother assumptions are restrictive. Only females who are no longer fertile themselves are eligible, and female fertility extends to age 45 years. Initially, there are very few eligible grandmothers and effects are small. Grandmothers can support only one dependent at a time and do not care selectively for their daughters'' offspring. They must take the oldest juveniles still relying on mothers; and infants under the age of 2 years are never eligible for subsidy. Our model includes no assumptions about brains, learning or pair bonds. Grandmother effects alone are sufficient to propel the doubling of life spans in less than sixty thousand years.     

Grandmothers and Children’s Schooling in Sub-Saharan Africa

Under poor circumstances, co-residence of a grandmother is generally considered to be beneficial for (grand)children. Empirical evidence does not unequivocally support this expectation and suggests that the grandmother’s importance depends on the family’s circumstances. We study the relationship between grandmother’s co-residence and children’s schooling in sub-Saharan Africa under a broad range of circumstances. Results make clear that the effect of a co-residing grandmother varies but is almost always positive. Grandmothers over age 60 are most effective in helping their (grand)children. They are particularly important for girls, and when the mother is deceased or not living in the household. Grandmothers are less effective in situations with few opportunities, as in very poor regions or in communities with few schooling opportunities. Our findings indicate that providing support to grandmothers should not be overlooked when designing policies aimed at strengthening the position of women and children in the sub-Saharan African context.     

Maternal grandmothers improve nutritional status and survival of children in rural Gambia

Hypotheses for the evolution of human female life-history characteristics have often focused on the social nature of human societies, which allows women to share the burden of childcare and provisioning amongst other members of their kin group. We test the hypothesis that child health and survival probabilities will be improved by the presence of kin using a longitudinal database from rural Gambia. We find that the only kin to improve the nutritional status of children significantly (apart from mothers) are maternal grandmothers, and that this is reflected in higher survival probabilities for children with living maternal grandmothers. There is also evidence that the reproductive status of the maternal grandmother influences child nutrition, with young children being taller in the presence of non-reproductive grandmothers than grandmothers who are still reproductively active. Paternal grandmothers and male kin, including fathers, have negligible impacts on the nutritional status and survival of children.     

The perils of climate change: In utero exposure to temperature variability and birth outcomes in the Andean region

The discussion on the effects of climate change on human activity has primarily focused on how increasing temperature levels can impair human health. However, less attention has been paid to the effect of increased climate variability on health. We investigate how in utero exposure to temperature variability, measured as the fluctuations relative to the historical local temperature mean, affects birth outcomes in the Andean region. Our results suggest that exposure to a temperate one standard deviation relative to the municipality’s long-term temperature mean during pregnancy reduces birth weight by 20 g. and increases the probability a child is born with low birth weight by a 0.7 percentage point. We also explore potential channels driving our results and find some evidence that increased temperature variability can lead to a decrease in health care and increased food insecurity during pregnancy.     

“Pensando Mucho” (“Thinking Too Much”): Embodied Distress Among Grandmothers in Nicaraguan Transnational Families

In this paper, I describe an embodied form of emotional distress expressed by Nicaraguan grandmothers caring for children of migrant mothers, “pensando mucho” (“thinking too much”). I draw on ethnographic fieldwork and semi-structured exploratory interviews about pensando mucho conducted with grandmother heads-of-household to show the cultural significance of this complaint within the context of women’s social roles as caregivers in transnational families. Adopting an interpretive and meaning-centered approach, I analyze the cultural significance of pensando mucho as expressed through women’s narratives about the impacts of mother outmigration on their personal and family lives. I show how women use pensando mucho to express the moral ambivalence of economic remittances and the uncertainty surrounding migration, particularly given cultural values for “unity” and “solidarity” in Nicaraguan family life. I also discuss the relationship between pensando mucho and dolor de cerebro (“brainache”) as a way of documenting the relationship between body/mind, emotional distress, and somatic suffering. The findings presented here suggest that further research on “thinking too much” is needed to assess whether this idiom is used by women of the grandmother generation in other cultural contexts to express embodied distress in relation to broader social transformations.     

Human aging and somatic point mutations in mtDNA: A comparative study of generational differences (grandparents and grandchildren)

The accumulation of somatic mutations in mtDNA is correlated with aging. In this work, we sought to identify somatic mutations in the HVS-1 region (D-loop) of mtDNA that might be associated with aging. For this, we compared 31 grandmothers (mean age: 63 ± 2.3 years) and their 62 grandchildren (mean age: 15 ± 4.1 years), the offspring of their daughters. Direct DNA sequencing showed that mutations absent in the grandchildren were detected in a presumably homoplasmic state in three grandmothers and in a heteroplasmic state in an additional 13 grandmothers; no mutations were detected in the remaining 15 grandmothers. However, cloning followed by DNA sequencing in 12 grandmothers confirmed homoplasia in only one of the three mutations previously considered to be homoplasmic and did not confirm heteroplasmy in three out of nine grandmothers found to be heteroplasmic by direct sequencing. Thus, of 12 grandmothers in whom mtDNA was analyzed by cloning, eight were heteroplasmic for mutations not detected in their grandchildren. In this study, the use of genetically related subjects allowed us to demonstrate the occurrence of age-related (> 60 years old) mutations (homoplasia and heteroplasmy). It is possible that both of these situations (homoplasia and heteroplasmy) were a long-term consequence of mitochondrial oxidative phosphorylation that can lead to the accumulation of mtDNA mutations throughout life.     

Association of Childhood Economic Hardship with Adult Height and Adult Adiposity among Hispanics/Latinos. The HCHS/SOL Socio-Cultural Ancillary Study

The study examined the association of childhood and current economic hardship with anthropometric indices in Hispanic/Latino adults, using data from the HCHS/SOL Socio-cultural ancillary study (N = 5,084), a community-based study of Hispanic/Latinos living in four urban areas (Bronx, NY, Chicago, IL, Miami, FL, and San Diego, CA). Childhood economic hardship was defined as having experienced a period of time when one’s family had trouble paying for basic needs (e.g., food, housing), and when this economic hardship occurred: between 0–12, 13–18 years old, or throughout both of those times. Current economic hardship was defined as experiencing trouble paying for basic needs during the past 12 months. Anthropometry included height, body mass index (BMI), waist circumference (WC), and percentage body fat (%BF). Complex survey linear regression models were used to test the associations of childhood economic hardship with adult anthropometric indices, adjusting for potential confounders (e.g., age, sex, Hispanic background). Childhood economic hardship varied by Hispanic background, place of birth, and adult socio-economic status. Childhood economic hardship during both periods, childhood and adolescence, was associated with shorter height. Childhood economic hardship was associated with greater adiposity among US born individuals only. Current economic hardship was significantly associated with all three measures of adiposity (BMI, WC, %BF). These findings suggest that previous periods of childhood economic hardship appear to influence adult height more than adiposity, whereas current economic hardship may be a better determinant of adult adiposity in Hispanics.     

Month of birth predicted reproductive success and fitness in pre-modern Canadian women

Conditions experienced during early development affect human health and survival in adulthood, but whether such effects have consequences for fitness is not known. One surrogate for early conditions is month of birth, which is known to influence health and survival in many human populations. We show that in nineteenth century Canada, month of birth predicted a woman's fitness measured by the number of grandchildren produced, with the genetic contribution to the following generations by women born in different months differing by over seven grandchildren. This difference was mainly caused by differences in the reproductive rates of both mothers and their offspring, rather than differences in their survival. Women born in the best months of the year had longer reproductive lifespans, larger numbers of live births and raised more offspring to adulthood than those who were born in the worst months. Furthermore, the offspring of those women born in the best months also had greater reproductive rates, suggesting that month of birth also influenced a mother's ability to invest in her offspring. Our results suggest that early conditions may have important consequences for human lifetime reproductive performance within and between generations, and that timing of birth had large effects on fitness in this rural community.     

Brief communication: Evaluating grandmother effects

Women who have outlived child‐bearing have long been described as postreproductive. But contributions they make to the survival or fertility of their descendants enhance the reproduction of their genes. Consequently, natural selection affects this characteristic stage of human life history. Grandmother effects can be measured in data sets that include births and deaths over several generations, but unmeasured covariates complicate the task. Here we focus on two complications: cohort shifts in mortality and fertility, and maternal age at death. We use the Utah Population Database to show that longevity of grandmothers may be associated with fewer grandchildren, as reported by Madrigal and Melendez‐Obando (Am J Phys Anthropol 136 (2008) 223–229) for a Costa Rican sample, even when grandmother effects are actually positive. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.     

Vervet monkey grandmothers: Interactions with infant grandoffspring

Social relationships of 30 infants with their maternal grandmothers were studied in a captive colony of vervet monkeys (Cercopithecus aethiops sabaeus).Grandmothers and grandinfants formed affiliative relationships with one another that could be distinguished from the infant’s relationships with nonkin adult females and with other adult female kin. The intensity of the grandmother—grandinfant relationship varied according to several factors which were related to the infant’s vulnerability to mortality and to the grandmother’s ability to provide effective social support. High-ranking grandmothers spent more time near their grandinfants, and initiated more grooming and caretaking of their grandinfants, than did lower-ranking grandmothers. Grandmothers spent more time near their daughter’s first surviving infant than near later-born infants, and when grandmothers had more than one adult daughter, they spent more time near the infant of the younger daughter. These results, combined with the fact that the presence of a maternal grandmother has been associated with a reduction in the rate of infant mortality in this colony (Fairbanks and McGuire, 1986), suggest that grandmothers are actively contributing to the reproductive success of their adult daughters and to the survival of their infant grandoffspring.     

The evolution of sex-specific grandparental harm

Recent empirical studies indicate that grandparents favour some categories of grandchildren over others. Here, we expand the previous theoretical foundation for this finding and show that grandchild-harming phenotypes are predicted to evolve by ‘sexually antagonistic zygotic drive (SA-zygotic drive) of the sex chromosomes’. We use the logic of Hamilton''s rule to develop a new ‘no-cost-to-self nepotism rule’ that greatly simplifies the determination of the invasion criteria for mutations that cause grandparents to harm grandchildren. We use this theory to generate predictions that distinguish SA-zygotic drive from theory based solely on paternity assurance. The major diagnostic prediction is that grandmothers, and to a lesser degree grandfathers, will evolve grandson-harming phenotypes that reduce the level of sib competition experienced by their more closely related granddaughters, especially in their sons'' families. This prediction is supported by data from recent studies showing (i) grandmothers invest more in granddaughters than grandsons, and counterintuitively, (ii) paternal grandmothers reduce the survival of their grandsons. We conclude that SA-zygotic drive is plausibly operating in humans via sexually antagonistic grandparental care.     

Transgenerational effects of childhood conditions on third generation health and education outcomes

This paper examines the extent to which pre-puberty nutritional conditions in one generation affect productivity-related outcomes in later generations. Recent findings from the biological literature suggest that the so-called slow growth period around age 9 is a sensitive period for male germ cell development. We build on this evidence and investigate whether undernutrition at those ages transmits to children and grandchildren. Our findings indicate that third generation males (females) tend to have higher mental health scores if their paternal grandfather (maternal grandmother) was exposed to a famine during the slow growth period. These effects appear to reflect biological responses to adaptive expectations about scarcity in the environment, and as such they can be seen as an economic correctional mechanism in evolution, with marked socio-economic implications for the offspring.     

Limb reduction defects in the first generation and deafness in the second generation of intrauterine exposed fetuses to diethylstilbestrol

Maternal treatment with diethylstilbestrol (DES) during pregnancy can produce vaginal adenocarcinoma and other abnormalities of the vagina in her daughters when they reach adolescence or adulthood, miscarriages and absence of full term infants. Concerning malformations in newborns whose mothers were treated with DES, clitoromegaly and malformations of the uterus were reported in females and genital lesions in males. However, the frequencies of major congenital anomalies were not greater than expected. We report three cases of limb reduction defects (LRD) in the first generation of children whose mothers were treated with DES during pregnancy, and two children (one male, one female) with deafness in the second generation after intrauterine exposure to DES. The LRD were not associated with other congenital anomalies. The malformed children with LRD were born between 1965 and 1973. The deafness was also isolated. The two mothers who have no hearing problems and who are healthy were exposed in utero to DES in 1963 and 1965, respectively. Their children were born in 1989 and 1994, respectively. In conclusion, the association of LRD and hearing loss with intrauterine exposure to DES could be coincidental. However, some hypothesis may explain these associations. Congenital hearing loss in the second generation may suggest a transgenerational effect.     

Factors associated with the intellectual ability of children born to women with high risk pregnancies.

The intellectual abilities of 242 children born to women who had been hypertensive during pregnancy were assessed at the age of 7 1/2 years. Associations between 15 maternal, fetal, perinatal, postnatal and environmental factors, and test scores were investigated. After adjustment for confounding variables children in the upper social classes, born to non-smokers, who were first born, breast fed, and with birth weights above the 10th centile had significantly higher scores in some aspects of ability than the rest. Children whose mothers had developed superimposed pre-eclampsia had higher scores than those whose mothers had not suffered preeclampsia; and children delivered by elective caesarean section had lower scores than those delivered spontaneously. In a small subgroup of women with particularly high risk pregnancies perinatal mortality had been 10 times greater than in the rest of the sample. At 7 1/2 years the intellectual ability of the survivors in this subgroup did not differ from that of the rest. These findings do not support the notion that there is a quantitative continuum of "reproductive casualty" from mortality to morbidity.