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Shreyer S. Variation in grandmaternal investment in Ukraine. Am J Hum Biol 2024:e24128. [PMID: 38963171 DOI: 10.1002/ajhb.24128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 05/21/2024] [Accepted: 06/23/2024] [Indexed: 07/05/2024] Open
Abstract
BACKGROUND Grandmothers vary in their contributions to grandchildren based on their relatedness and the sex of the child. Maternal grandmothers decrease grandchildren's risk of mortality and increase grandchildren's health more significantly than paternal grandmothers, but limited evidence suggests that paternal grandmothers may invest more in female than male grandchildren. AIMS In this study, I test whether contact frequency between grandmothers and grandchildren is influenced by their relatedness (maternal vs paternal) or the sex of the child. This research was carried out in Ukraine because it is neither matrilocal nor patrilocal, and Ukrainian grandmothers are known to provide a high rate of childcare. METHODS This study included interviews with 60 grandmothers that asked about contact frequency with grandchildren, relatedness (maternal or paternal), and contact frequency between the grandchild and the other grandmother. A dataset generated for each grandchild (n = 128) included sex, age, and contact frequency with both maternal and paternal grandmothers. Linear mixed models were fit to the data to explore the relationship between grandmother relatedness and contact frequency. RESULTS On average, maternal grandmothers saw their grandchildren 173.8 days/year, while paternal grandmothers saw their grandchildren 87.5 days/year (p < 0.001). The sex of the child was not a significant factor in determining contact frequency. CONCLUSION In Ukraine, maternal grandmothers have more frequent contact with their grandchildren. This finding supports the idea that grandmaternal investment is an evolutionarily adaptive strategy. However, the bias towards maternal grandmothers may also be explained by a post-socialist cultural context, which necessitates grandmaternal care.
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Affiliation(s)
- Sofiya Shreyer
- University of Massachusetts, Amherst, Massachusetts, USA
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2
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Helle S, Tanskanen AO, Coall DA, Perry G, Daly M, Danielsbacka M. Investment by maternal grandmother buffers children against the impacts of adverse early life experiences. Sci Rep 2024; 14:6815. [PMID: 38514748 PMCID: PMC10957867 DOI: 10.1038/s41598-024-56760-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 03/11/2024] [Indexed: 03/23/2024] Open
Abstract
Exogenous shocks during sensitive periods of development can have long-lasting effects on adult phenotypes including behavior, survival and reproduction. Cooperative breeding, such as grandparental care in humans and some other mammal species, is believed to have evolved partly in order to cope with challenging environments. Nevertheless, studies addressing whether grandparental investment can buffer the development of grandchildren from multiple adversities early in life are few and have provided mixed results, perhaps owing to difficulties drawing causal inferences from non-experimental data. Using population-based data of English and Welsh adolescents (sample size ranging from 817 to 1197), we examined whether grandparental investment reduces emotional and behavioral problems in children resulting from facing multiple adverse early life experiences (AELEs), by employing instrumental variable regression in a Bayesian structural equation modeling framework to better justify causal interpretations of the results. When children had faced multiple AELEs, the investment of maternal grandmothers reduced, but could not fully erase, their emotional and behavioral problems. No such result was observed in the case of the investment of other grandparent types. These findings indicate that in adverse environmental conditions the investment of maternal grandmothers can improve child wellbeing.
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Affiliation(s)
- Samuli Helle
- INVEST Research Flagship Centre, University of Turku, Turku, Finland.
| | - Antti O Tanskanen
- Population Research Institute, Väestöliitto, Helsinki, Finland
- Department of Social Research, University of Turku, Turku, Finland
| | - David A Coall
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia
| | - Gretchen Perry
- School of Social Work, University of Canterbury, Christchurch, New Zealand
| | - Martin Daly
- Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada
| | - Mirkka Danielsbacka
- INVEST Research Flagship Centre, University of Turku, Turku, Finland
- Population Research Institute, Väestöliitto, Helsinki, Finland
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Wak G, Bangha M, Aborigo R, Anarfi J, Kwankye S. Impact of kinship support on child mortality in the Upper East Region of Ghana: assessing the Grandmother Hypothesis. Int Health 2023; 15:744-751. [PMID: 37317981 PMCID: PMC10629956 DOI: 10.1093/inthealth/ihad041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 03/14/2023] [Accepted: 05/22/2023] [Indexed: 06/16/2023] Open
Abstract
BACKGROUND The grandmother is an important kin member whose contribution to childcare and survival has been recognized in the literature, hence the Grandmother Hypothesis. This article examines the effect of the presence of a grandmother on child mortality. METHODS Data were obtained from the Navrongo Health and Demographic Surveillance System, located in the Upper East Region of Ghana. Children born between January 1999 and December 2018 were included in the analysis. Person-months lived for each child were generated. The multilevel Poisson regression technique was employed to investigate the effect of a grandmother on child survival. RESULTS In all, 57 116 children were included in the analysis, of which 7% died before age 5 y. Person-months were generated for the children, which produced 2.7 million records, with about 487 800 person-years. After controlling for confounders, results showed that children in households with paternal grandmothers are 11% less likely to die compared with those without paternal grandmothers. However, when other confounders were taken into accounts, the beneficial effect of maternal grandmothers disappeared. CONCLUSIONS We conclude that the presence of grandmothers improves child survival, thus sustaining the Grandmother Hypothesis. The experiences of these grandmothers should be tapped to improve child survival, particularly in rural areas.
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Affiliation(s)
- George Wak
- Navrongo Health Research Centre, Ghana
- School of Public Health, University of Health and Allied Sciences, Ghana
| | - Martin Bangha
- African Population and Health Research Center, Nairobi, Kenya
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Fox MM, Knorr DA, Kwon D, Wiley KS, Parrish MH. How prenatal cortisol levels relate to grandmother-mother relationships among a cohort of Latina women. Am J Hum Biol 2023; 35:e23883. [PMID: 36862026 PMCID: PMC10474942 DOI: 10.1002/ajhb.23883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 02/09/2023] [Accepted: 02/10/2023] [Indexed: 03/03/2023] Open
Abstract
INTRODUCTION As part of the human reproductive strategy, mothers receive childcare assistance from others. For kin, allomothers are adaptively incentivized to provide assistance due to inclusive fitness benefits. Previous studies across a broad range of populations identify grandmothers as particularly consistent allomothers. Minimal attention has been paid to the possibility that allomothers may begin investing in offspring quality during the prenatal stage of life. Here, we innovate within the area of grandmother allocare research by examining the prenatal stage of life and biopsychosocial mechanisms by which prenatal grandmother effects may be enacted. METHODS Data derive from the Mothers' Cultural Experiences study, a cohort of 107 pregnant Latina women in Southern California. At <16 weeks' gestation, we administered questionnaires, collected morning urine samples, and measured cortisol by enzyme-linked immunosorbent assay, correcting for specific gravity. We measured the soon-to-be maternal and paternal grandmothers' relationship quality, social support, frequency of seeing each other, communicating, and geographic proximity to pregnant mothers, that is, their daughters and daughters-in-law. These measures were self-reported by the pregnant mothers. We assessed how grandmother constructs related to the pregnant women's depression, stress, anxiety, and cortisol levels. RESULTS We observed benefits conferred by maternal grandmothers for mothers' prenatal mental health and lower cortisol levels. Paternal grandmothers also conferred mental health benefits to pregnant daughters-in-law, but higher cortisol levels. CONCLUSION Our results suggest that grandmothers, especially maternal grandmothers, are able to improve their inclusive fitness by caring for pregnant daughters, and allomother support may positively impact prenatal health. This work extends the traditional cooperative breeding model by identifying a prenatal grandmother effect, and, by examining a maternal biomarker.
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Affiliation(s)
- Molly M. Fox
- Department of Anthropology, University of California, Los Angeles, Los Angeles, CA, 90095 USA
- Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA, 90095 USA
| | - Delaney A. Knorr
- Department of Anthropology, University of California, Los Angeles, Los Angeles, CA, 90095 USA
| | - Dayoon Kwon
- Department of Epidemiology, UCLA Fielding School of Public Health, University of California, Los Angeles, Los Angeles, CA, 90095 USA
| | - Kyle S. Wiley
- Department of Anthropology, University of California, Los Angeles, Los Angeles, CA, 90095 USA
| | - Michael H. Parrish
- Department of Psychology, University of California, Los Angeles, CA 90095 USA
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Chapman S, Danielsbacka M, Tanskanen AO, Lahdenperä M, Pettay J, Lummaa V. Grandparental co-residence and grandchild survival: the role of resource competition in a pre-industrial population. Behav Ecol 2023; 34:446-456. [PMID: 37192925 PMCID: PMC10183204 DOI: 10.1093/beheco/arad013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 02/08/2023] [Accepted: 02/24/2023] [Indexed: 03/29/2023] Open
Abstract
Although grandparents are and have been important alloparents to their grandchildren, they are not necessarily only beneficial but can also compete with grandchildren over limited resources. Competition over parental care or other resources may exist especially if grandparents live in the same household with grandchildren and it can be dependent on grandchild age. By utilizing demographic data collected from historic population registers in Finland between 1761 and 1895 (study sample n = 4041) we investigate whether grandparents living in the same household with grandchildren are detrimental or beneficial for grandchild survival. Having a living but not co-residing grandmother or grandfather were both associated with better survival whereas having a co-resident grandfather was associated with lower chance to survive for infants (age < 1 year). Separating the effect between maternal and paternal grandparents and grandmothers and grandfathers revealed no differences in the effects between lineages. Negative effect of having a co-residing grandfather was not significant when grandfathers were separated for lineage specific models. These results implicate that accounting for the co-residence status and child's age, grandparents were mostly beneficial when not co-residing with very young children and that having a co-residing grandfather at that age could be associated with lower chances to survive. Predictions made by grandmother hypothesis and resource competition both received support. The results presented here also offered comparison points to preindustrial and contemporary three-generational families.
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Affiliation(s)
- Simon Chapman
- Department of Social Research, University of Turku, Turku, Finland
| | - Mirkka Danielsbacka
- Department of Social Research, University of Turku, Turku, Finland
- Population Research Institute, Helsinki, Finland
| | - Antti O Tanskanen
- Department of Social Research, University of Turku, Turku, Finland
- Population Research Institute, Helsinki, Finland
| | | | - Jenni Pettay
- Department of Social Research, University of Turku, Turku, Finland
| | - Virpi Lummaa
- Department of Biology, University of Turku, Turku, Finland
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Blagosklonny MV. Are menopause, aging and prostate cancer diseases? Aging (Albany NY) 2023; 15:298-307. [PMID: 36707068 PMCID: PMC9925691 DOI: 10.18632/aging.204499] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 01/16/2023] [Indexed: 01/28/2023]
Abstract
There is no doubt that prostate cancer is a disease. Then, according to hyperfunction theory, menopause is also a disease. Like all age-related diseases, it is a natural process, but is also purely harmful, aimless and unintended by nature. But exactly because these diseases (menopause, prostate enlargement, obesity, atherosclerosis, hypertension, diabetes, presbyopia and thousands of others) are partially quasi-programmed, they can be delayed by slowing aging. Is aging a disease? Aging is a quasi-programmed disease that is partially treatable by rapamycin. On the other hand, aging is an abstraction, a sum of all quasi-programmed diseases and processes. In analogy, the zoo consists of animals and does not exist without animals, but the zoo is not an animal.
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Dai X, Williams G, Lin S, Baker C, Wu M, Du W, Hua J. The sibling effect on neurodevelopment of preschoolers under China's newly relaxed child policy: A national retrospective cohort study. Front Psychol 2022; 13:988622. [PMID: 36562065 PMCID: PMC9764001 DOI: 10.3389/fpsyg.2022.988622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 11/22/2022] [Indexed: 12/12/2022] Open
Abstract
Introduction The change in Chinese fertility policy brings new challenges and considerations for children's health outcomes; however, very little is known about the interaction between siblings, family socioeconomic status (SES), and neurodevelopment in the Chinese preschool-age population. Therefore, this study aimed to develop a new explanatory pathway from sibling effect to early childhood development and explored the mediation effect of family SES in the pathway. Methods From April 2018 to December 2019, we conducted a national retrospective cohort study in 551 cities in China, and a total of 115,915 preschool-aged children were selected for the final analysis. Children's neurodevelopment, including Communication, Gross motor, Fine motor, Problem-solving, and Personal-social, was assessed with the Ages & Stages Questionnaires, Third Edition (ASQ-3). Hypothesis tests and multilevel regression models were used to assess the associations and their strength between sibling effect and neurodevelopmental delay. Pathway analysis was used to verify the mediation effect of SES. Results The results showed that there were significant risk effects of a sibling on preschoolers' overall neurodevelopment including communication, gross motor, fine motor, and problem-solving delay. The adjustment of family SES, however, brought a reversal of this association. The results of the mediation model illustrated a direct, protective effect of one-sibling status (βASQ-delay = -0.09; βASQ-scores = 0.07; p < 0.001), and an indirect, risk effect from one-sibling status through family SES to neurodevelopment outcomes (βASQ-delay =0.12; βASQ-scores = -0.12; p < 0.001). The total sibling effect was weakened but remained negative (βASQ-delay =0.03; βASQ-scores = -0.05; p < 0.001). Discussion This study concluded that family SES mediated the negative effects of one sibling on early child development. To enhance the positive influence of sibling addition, we suggested providing more resources and instructions to the families with less educated and poorer employed parents under the coming multi-child era.
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Affiliation(s)
- Xiaotian Dai
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, Shanghai, China,School of Social Science, Nottingham Trent University, Nottingham, United Kingdom
| | - Gareth Williams
- School of Social Science, Nottingham Trent University, Nottingham, United Kingdom
| | - Senran Lin
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Charlie Baker
- NTU Psychology, School of Social Science, Nottingham Trent University, Nottingham, United Kingdom
| | - Meiqin Wu
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Wenchong Du
- NTU Psychology, School of Social Science, Nottingham Trent University, Nottingham, United Kingdom,*Correspondence: Wenchong Du, ; Jing Hua,
| | - Jing Hua
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, Shanghai, China,*Correspondence: Wenchong Du, ; Jing Hua,
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8
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Vázquez‐Vázquez ADP, Fewtrell MS, Chan‐García H, Batún‐Marrufo C, Dickinson F, Wells JCK. Do maternal grandmothers influence breastfeeding duration and infant nutrition? Evidence from Merida, Mexico. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2022; 179:444-459. [PMID: 36790606 PMCID: PMC9826188 DOI: 10.1002/ajpa.24623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/25/2022] [Accepted: 08/29/2022] [Indexed: 11/10/2022]
Abstract
OBJECTIVES Breast-feeding is sensitive to somatic, hormonal, behavioral and psychological components of maternal capital. However, through grandmothering, older women may also influence breast-feeding by transferring informational resources to their daughters. We hypothesized that mothers with prolonged instrumental support from their own mother are more likely to have received advice and to have favorable attitudes/practices regarding breastfeeding, compared to those lacking such support, with implications for the grandchild's somatic capital. METHODS We recruited 90 mother-infant dyads (52 with grandmaternal support, 38 without) in Merida, Yucatan, Mexico. All children were first-borns, aged ~2 years. Anthropometry and body composition were assessed. Data on grandmother's breastfeeding advice and maternal breastfeeding duration were obtained by questionnaire. Maternal attitudes to breast-feeding were assessed using the Iowa Infant Feeding Attitude Scale. RESULTS Women with instrumental support were more likely to have received grandmaternal advice during pregnancy/infancy on exclusive breast-feeding duration (60% vs. 37%, p = 0.033) and the type of first complementary food (81% vs. 47%, p = 0.001). However, women with support had a less favorable attitude to breastfeeding than those without and breastfed their children for less time (median 5 vs. 10.5 months, p = 0.01). No group differences were found in children's length, weight, skinfolds or lean mass z-score. DISCUSSION Although grandmothers providing instrumental support provided advice regarding breastfeeding, their attitudes may reflect issues beyond nutritional health. Advice of maternal grandmothers did not promote extended breastfeeding, however the differences in breastfeeding attitudes were not associated with the children's nutritional status. Grandmothers should be included in public health interventions promoting breastfeeding.
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Affiliation(s)
| | - Mary S. Fewtrell
- Childhood Nutrition Research Centre, UCLGreat Ormond Street Institute of Child HealthLondonUK
| | - Hidekel Chan‐García
- Human Ecology DepartmentCentre for Research and Advanced Studies (Cinvestav)MeridaYucatanMexico
| | - Carolina Batún‐Marrufo
- Human Ecology DepartmentCentre for Research and Advanced Studies (Cinvestav)MeridaYucatanMexico
| | - Federico Dickinson
- Human Ecology DepartmentCentre for Research and Advanced Studies (Cinvestav)MeridaYucatanMexico
| | - Jonathan C. K. Wells
- Childhood Nutrition Research Centre, UCLGreat Ormond Street Institute of Child HealthLondonUK
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9
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Grandpaternal care and child survival in a pastoralist society in western China. EVOL HUM BEHAV 2022. [DOI: 10.1016/j.evolhumbehav.2022.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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10
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Nelson RG. Theoretical constraints: Science, caretaking, and the creation of normative ideals. Am J Hum Biol 2021; 33:e23650. [PMID: 34291528 DOI: 10.1002/ajhb.23650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 05/19/2021] [Accepted: 06/30/2021] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVES This review explores the dualism in evolutionary anthropology that both acknowledges a broad range of familial caretaking strategies, while also remaining tethered to theories scaffolded around notions of selfish genes that constrain our understanding of who provides adequate kin care. I examine the process of norm creation in the sciences by investigating how theory may limit which data are collected and how those data are interpreted. METHODS This paper serves as a literature review and critique of prominent biological, evolutionary, and psychological conceptualizations of parental investment and caretaking in humans, and how these studies shape what is considered normal behavior in scientific literature. RESULTS Quantification, assessment, and theory building in evolutionary anthropology, and an oversampling of WEIRD communities in other disciplines, have limited our understanding of what constitutes both evolutionarily adaptive behaviors, and culturally specific human behaviors. CONCLUSIONS A synthetic theoretical model of behavioral norms in childrearing must account for an exchange of psycho-social and cultural resources and skills, the transfer of energetic reserves via gestation and lactation, and the indirect benefits of genetic inheritance. The emphasis on tailoring data collection to fit evolutionary theories of the family has limited our ability to understand the diverse proximate mechanisms that humans employ in taking care of kin as biocultural reproducers.
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Affiliation(s)
- Robin G Nelson
- Department of Anthropology, Santa Clara University, Santa Clara, California, USA
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11
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Starkweather KE, Keith MH, Prall SP, Alam N, Zohora F, Emery Thompson M. Are fathers a good substitute for mothers? Paternal care and growth rates in Shodagor children. Dev Psychobiol 2021; 63:e22148. [PMID: 34087947 DOI: 10.1002/dev.22148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 05/18/2021] [Accepted: 05/20/2021] [Indexed: 12/21/2022]
Abstract
Biparental care is a hallmark of human social organization, though paternal investment varies between and within societies. The facultative nature of paternal care in humans suggests males should invest when their care improves child survival and/or quality, though testing this prediction can be challenging because of the difficulties of empirically isolating paternal effects from those of other caregivers. Additionally, the broader context in which care is provided, vis-à-vis care from mothers and others, may lead to different child outcomes. Here, we examine the effects of paternal care on child growth among Shodagor fisher-traders, where fathers provide high levels of both additive and substitutive care, relative to mothers. We modeled seasonal z-scores and velocities for height, weight, and body mass index (BMI) outcomes using linear mixed models. Our evidence indicates that, as predicted, the context of paternal care is an important predictor of child outcomes. Results show that environmental seasonality and alloparental help contribute to a nuanced understanding of the impact of Shodagor paternal care on child physiology.
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Affiliation(s)
- K E Starkweather
- Department of Anthropology, University of Illinois Chicago, Chicago, Illinois.,Department of Anthropology, University of New Mexico, Albuquerque, New Mexico.,Department of Human Behavior, Ecology, and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - M H Keith
- Department of Anthropology, University of Washington, Seattle, Washington
| | - S P Prall
- Department of Anthropology, University of Missouri, Columbia, Missouri
| | - N Alam
- Health Systems and Population Studies Division, ICDDR,B, Dhaka, Bangladesh
| | - F Zohora
- Health Systems and Population Studies Division, ICDDR,B, Dhaka, Bangladesh
| | - M Emery Thompson
- Department of Anthropology, University of New Mexico, Albuquerque, New Mexico
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12
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Offspring fertility and grandchild survival enhanced by maternal grandmothers in a pre-industrial human society. Sci Rep 2021; 11:3652. [PMID: 33574488 PMCID: PMC7878921 DOI: 10.1038/s41598-021-83353-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 02/02/2021] [Indexed: 01/30/2023] Open
Abstract
Help is directed towards kin in many cooperative species, but its nature and intensity can vary by context. Humans are one of few species in which grandmothers invest in grandchildren, and this may have served as an important driver of our unusual life history. But helping behaviour is hardly uniform, and insight into the importance of grandmothering in human evolution depends on understanding the contextual expression of helping benefits. Here, we use an eighteenth-nineteenth century pre-industrial genealogical dataset from Finland to investigate whether maternal or paternal grandmother presence (lineage relative to focal individuals) differentially affects two key fitness outcomes of descendants: fertility and survival. We found grandmother presence shortened spacing between births, particularly at younger mother ages and earlier birth orders. Maternal grandmother presence increased the likelihood of focal grandchild survival, regardless of whether grandmothers had grandchildren only through daughters, sons, or both. In contrast, paternal grandmother presence was not associated with descendants' fertility or survival. We discuss these results in terms of current hypotheses for lineage differences in helping outcomes.
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Sadruddin AFA, Ponguta LA, Zonderman AL, Wiley KS, Grimshaw A, Panter-Brick C. How do grandparents influence child health and development? A systematic review. Soc Sci Med 2019; 239:112476. [PMID: 31539783 DOI: 10.1016/j.socscimed.2019.112476] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 07/31/2019] [Accepted: 08/01/2019] [Indexed: 01/09/2023]
Abstract
Grandparents are often a key source of care provision for their grandchildren, yet they are sidelined in caregiving research and policy decisions. We conducted a global, systematic review of the literature to examine the scope and quality of studies to date (PROSPERO database CRD42019133894). We screened 12,699 abstracts across 7 databases, and identified 206 studies that examined how grandparents influence child health and development. Indicators of grandparent involvement were contact, caregiving behaviors, and financial support. Our review focused on two research questions: how do grandparents influence child health and development outcomes, and what range of child outcomes is reported globally? We examined study design, sample characteristics, key findings, and outcomes pertaining to grandchildren's physical health, socio-emotional and behavioral health, and cognitive and educational development. Our search captured studies featuring grandparent custodial care (n = 35), multigenerational care (n = 154), and both types of care (n = 17). We found substantial heterogeneity in the data provided on co-residence, caregiving roles, resources invested, outcomes, and mechanisms through which "grandparent effects" are manifested. We identified two important issues, related to operationalizing indicators of grandparent involvement and conceptualizing potential mechanisms, leading to gaps in the evidence base. Currently, our understanding of the pathways through which grandparents exert their influence is constrained by limited data on what grandparents actually do and insufficient attention given to interpersonal and structural contexts. We present a conceptual framework to explicitly measure and theorize pathways of care, with a view to inform research design and policy implementation. We underscore the need for more robust data on three indicators of caregiver involvement-contact, behavior, and support-and for careful description of structural and interpersonal contexts in caregiving research.
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Margolis R, Verdery AM. A Cohort Perspective on the Demography of Grandparenthood: Past, Present, and Future Changes in Race and Sex Disparities in the United States. Demography 2019; 56:1495-1518. [PMID: 31270779 PMCID: PMC6667684 DOI: 10.1007/s13524-019-00795-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
How has the demography of grandparenthood changed over the last century? How have racial inequalities in grandparenthood changed, and how are they expected to change in the future? Massive improvements in mortality, increasing childlessness, and fertility postponement have profoundly altered the likelihood that people become grandparents as well as the timing and length of grandparenthood for those that do. The demography of grandparenthood is important to understand for those taking a multigenerational perspective of stratification and racial inequality because these processes define the onset and duration of intergenerational relationships in ways that constrain the forms and levels of intergenerational transfers that can occur within them. In this article, we discuss four measures of the demography of grandparenthood and use simulated data to estimate the broad contours of historical changes in the demography of grandparenthood in the United States for the 1880-1960 birth cohorts. Then we examine race and sex differences in grandparenthood in the past and present, which reveal declining inequality in the demography of grandparenthood and a projection of increasing group convergence in the coming decades.
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Affiliation(s)
- Rachel Margolis
- Department of Sociology, University of Western Ontario, Social Science Centre 5326, London, Ontario, N5A 5C2, Canada.
| | - Ashton M Verdery
- Department of Sociology and Criminology, Pennsylvania State University, 211 Oswald Tower, University Park, PA, 16802, USA
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Rosenbaum S, Gettler LT. With a little help from her friends (and family) part I: the ecology and evolution of non-maternal care in mammals. Physiol Behav 2019; 193:1-11. [PMID: 29933836 DOI: 10.1016/j.physbeh.2017.12.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 11/27/2017] [Accepted: 12/20/2017] [Indexed: 10/28/2022]
Abstract
In the class Mammalia, most young are cared for exclusively by their mothers. In species where mothers receive help, however, non-maternal caregivers may play a crucial role in development and life history trajectories. In turn, recipients of such care may have important impacts on caregivers of all types. In Part I of this overview, we briefly review the evolutionary barriers to widespread non-maternal care in mammals, and explain why the exceptions are of particular theoretical importance. We also summarize the current understanding of the selective forces leading to non-maternal care, and the taxa and types of caretakers amongst which it occurs. Finally, we argue for a fresh look at the categorization schemes that have traditionally been used to separate various types of mammalian non-maternal caregivers. This two-part introduction is aimed at scientists from multiple disciplines who study diverse organismal systems. It draws from the social and biological sciences literatures to provide an overview of this special issue of Physiology and Behavior's suite of methodological offerings and theoretical underpinnings.
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Affiliation(s)
- Stacy Rosenbaum
- Department of Anthropology, Northwestern University, Evanston, IL, United States; Davee Center for Epidemiology and Endocrinology, Lincoln Park Zoo, Chicago, IL, United States.
| | - Lee T Gettler
- Department of Anthropology, University of Notre Dame, Notre Dame, IN, United States; The Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States
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Abstract
Exceptional longevity represents an extreme phenotype. Current centenarians are survivors of a cohort who display delayed onset of age-related diseases and/or resistance to otherwise lethal illnesses occurring earlier in life. Characteristics of aging are heterogeneous, even among long-lived individuals. Associations between specific clinical or genetic biomarkers exist, but there is unlikely to be a single biomarker predictive of long life. Careful observations in the oldest old offer some empirical strategies that favor increased health span and life span, with implications for compression of disability, identification and implementation of lifestyle behaviors that promote independence, identification and measurement of more reliable markers associated with longevity, better guidance for appropriate health screenings, and promotion of anticipatory health discussions in the setting of more accurate prognostication. Comprehensive PubMed literature searches were performed, with an unbiased focus on mechanisms of longevity. Overall, the aggregate literature supports that the basis for exceptional longevity is multifactorial and involves disparate combinations of genes, environment, resiliency, and chance, all of which are influenced by culture and geography.
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Affiliation(s)
- Robert J Pignolo
- Division of Geriatric Medicine and Gerontology, Mayo Clinic, Rochester, MN.
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Schrijner S, Smits J. Grandmothers and Children's Schooling in Sub-Saharan Africa. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2018; 29:65-89. [PMID: 29222651 PMCID: PMC5846866 DOI: 10.1007/s12110-017-9306-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
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.
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Affiliation(s)
- Sandor Schrijner
- Department of Economics, Institute for Management Research, Radboud University, PO Box 9108, 6500HK, Nijmegen, The Netherlands.
| | - Jeroen Smits
- Department of Economics, Institute for Management Research, Radboud University, PO Box 9108, 6500HK, Nijmegen, The Netherlands
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18
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Schrijner S, Smits J. Grandparents and Children's stunting in sub-Saharan Africa. Soc Sci Med 2018; 205:90-98. [PMID: 29677583 DOI: 10.1016/j.socscimed.2018.03.037] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 03/19/2018] [Accepted: 03/23/2018] [Indexed: 02/08/2023]
Abstract
Globally an estimated 159 million children under 5 years of age are being too short for one's age (stunted). More than one third of these children is living in Africa. Given the substantial number of sub-Saharan African (SSA) children living in households with co-residing grandparents and the negative effects of stunting on productivity and economic growth, gaining insight into the role grandparents play for children's stunting, has become increasingly important. By applying multilevel logistic regression analysis on a database with information on 344,748 children aged 6-60 months living in 31 SSA countries, the strength of the relationship between grandparental co-residence and children's stunting is examined. Interaction analysis is used to explore how this relationship is moderated by characteristics of the household and of the context in which the household is situated. Children in households with a co-residing grandmother have significantly lower odds of being stunted than other children, provided that the grandmother is in the 50-75 age range. When the grandmother is very young or very old, the likelihood of being stunted is higher. For grandfathers, no significant overall relationship is found, but our findings show that co-residence of a grandfather is associated with less stunting of girls, in poor households and in polygamous households.
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Affiliation(s)
- Sandor Schrijner
- Department of Economics, Institute for Management Research, Radboud University, The Netherlands.
| | - Jeroen Smits
- Department of Economics, Institute for Management Research, Radboud University, The Netherlands
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19
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Zang E, Campbell C. Males' Later-Life Mortality Consequences of Coresidence With Paternal Grandparents: Evidence From Northeast China, 1789-1909. Demography 2018; 55:435-457. [PMID: 29492799 DOI: 10.1007/s13524-018-0653-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In this study, we investigate the effect of early-life coresidence with paternal grandparents on male mortality risks in adulthood and older age in northeast China from 1789 to 1909. Despite growing interest in the influence of grandparents on child outcomes, few studies have examined the effect of coresidence with grandparents in early life on mortality in later life. We find that coresidence with paternal grandmothers in childhood is associated with higher mortality risks for males in adulthood. This may reflect the long-term effects of conflicts between mothers and their mothers-in-law. These results suggest that in extended families, patterns of coresidence in childhood may have long-term consequences for mortality, above and beyond the effects of common environmental and genetic factors, even when effects on childhood mortality are not readily apparent.
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Affiliation(s)
- Emma Zang
- Sanford School of Public Policy, Duke University, Durham, NC, USA.
| | - Cameron Campbell
- Division of Social Science, The Hong Kong University of Science and Technology, Hong Kong, China.,School of History and Culture, Central China Normal University, Wuhan, China
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Chapman SN, Pettay JE, Lummaa V, Lahdenperä M. Limited support for the X-linked grandmother hypothesis in pre-industrial Finland. Biol Lett 2018; 14:rsbl.2017.0651. [PMID: 29321245 DOI: 10.1098/rsbl.2017.0651] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 12/11/2017] [Indexed: 01/28/2023] Open
Abstract
The level of kin help often depends on the degree of relatedness between a helper and the helped. In humans, grandmother help is known to increase the survival of grandchildren, though this benefit can differ between maternal grandmothers (MGMs) and paternal grandmothers (PGMs) and between grandsons and granddaughters. The X-linked grandmother hypothesis posits that differential X-chromosome relatedness between grandmothers and their grandchildren is a leading driver of differential grandchild survival between grandmother lineages and grandchild sexes. We tested this hypothesis using time-event models on a large, multigenerational dataset from pre-industrial Finland. We found that the presence of an MGM increases grandson survival more than PGM presence, and that granddaughter survival is higher than that of grandsons in the presence of a PGM. However, there was no support for the key prediction that the presence of PGMs improves granddaughter survival more than that of MGMs, diminishing the overall support for the hypothesis. Our results call for alternative explanations for differences in the effects of maternal and paternal kin to grandchild survival in humans.
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Affiliation(s)
- Simon N Chapman
- Department of Biology, University of Turku, Turku 20014, Finland
| | - Jenni E Pettay
- Department of Biology, University of Turku, Turku 20014, Finland
| | - Virpi Lummaa
- Department of Biology, University of Turku, Turku 20014, Finland
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21
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Postmarital residence and child sex selection: Evidence from northeastern Japan, 1716–1870. DEMOGRAPHIC RESEARCH 2017. [DOI: 10.4054/demres.2017.37.43] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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Huber S, Zahourek P, Fieder M. Living with own or husband's mother in the household is associated with lower number of children: a cross-cultural analysis. ROYAL SOCIETY OPEN SCIENCE 2017; 4:170544. [PMID: 29134068 PMCID: PMC5666251 DOI: 10.1098/rsos.170544] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 09/27/2017] [Indexed: 06/07/2023]
Abstract
It has been discussed in the literature that the presence of kin, particularly the presence of a women's own mother or her mother in law, may have fertility effects. We aimed to examine the effects of the presence of a woman's own or her husband's mother in the household on a woman's fertility in terms of number of children on a broad basis by analysing census data of over two million married women aged between 15 and 34 years from 14 countries worldwide. We find that with the exception of Iraq, across all countries, the majority of women live only with their spouse in the household. We further find that the presence of any mother in the household is invariably associated with a significantly lower number of children compared to women living only with their spouse. In addition, in most countries, a woman's number of children is lower if she lives with her own mother as compared to her husband's mother in the household. Number of children is nonlinearly associated with woman's age, the presence of any mother being related with an earlier start of childbearing but a shallower increase in number of children. We speculate that the presence of a mother in the household may slow down woman's reproduction, but also discuss alternative explanations.
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Affiliation(s)
| | | | - Martin Fieder
- Department of Anthropology, University of Vienna, Vienna, Austria
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23
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Abstract
Evolutionary studies have shown that in many traditional populations the beneficial effects of grandparental presence for grandchildren may vary according to the sex and lineage of the grandparents, as well as by the sex of the grandchild. However, few studies have investigated the relevance of these factors in modern developed societies. The present investigation uses the Millennium Cohort Study (n = 4,636 children) to analyse the association between grandparental investment and child development in contemporary England. Grandparental investment is measured by parent-grandparent contact frequencies at the child’s age of 3 and child development by “early learning goals” over the first year of primary school assessed with the Foundation Stage Profile (FSP). Children whose mothers reported contacts with maternal grandparents receive higher FSP scores compared to those with no contact at all. In addition, children whose fathers reported daily contacts with paternal grandfathers have lower FSP scores than other children. The study provides evidence of the relevance of grandparental investment on grandchild development also in developed societies. The results are discussed with reference to the grandmother hypothesis, sex-specific reproductive strategies and sex chromosome hypothesis.
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Dong H, Manfredini M, Kurosu S, Yang W, Lee JZ. Kin and birth order effects on male child mortality: three East Asian populations, 1716-1945 .. EVOL HUM BEHAV 2017; 38:208-216. [PMID: 28781514 PMCID: PMC5542571 DOI: 10.1016/j.evolhumbehav.2016.10.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human child survival depends on adult investment, typically from parents. However, in spite of recent research advances on kin influence and birth order effects on human infant and child mortality, studies that directly examine the interaction of kin context and birth order on sibling differences in child mortality are still rare. Our study supplements this literature with new findings from large-scale individual-level panel data for three East Asian historical populations from northeast China (1789-1909), northeast Japan (1716-1870), and north Taiwan (1906-1945), where preference for sons and first-borns is common. We examine and compare male child mortality risks by presence/absence of co-resident parents, grandparents, and other kin, as well as their interaction effects with birth order. We apply discrete-time event-history analysis on over 172,000 observations of 69,125 boys aged 1-9 years old. We find that in all three populations, while the presence of parents is important for child survival, it is more beneficial to first/early-borns than to later-borns. Effects of other co-resident kin are however null or inconsistent between populations. Our findings underscore the importance of birth order in understanding how differential parental investment may produce child survival differentials between siblings.
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Affiliation(s)
- Hao Dong
- Princeton University, Princeton, USA
| | | | | | | | - James Z. Lee
- The Hong Kong University of Science and Technology, Hong Kong, China
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Takahashi M, Singh RS, Stone J. A Theory for the Origin of Human Menopause. Front Genet 2017; 7:222. [PMID: 28111590 PMCID: PMC5216033 DOI: 10.3389/fgene.2016.00222] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 12/13/2016] [Indexed: 11/25/2022] Open
Abstract
A complete and compelling evolutionary explanation for the origin of human menopause is wanting. Menopause onset is defined clinically as the final menses, confirmed after 1 year without menstruation. The theory proposed herein explains at multiple levels - ultimately genetic but involving (1) behavioral, (2) life history, and (3) social changes - the origin and evolution of menopause in women. Individuals in Lower Paleolithic human populations were characterized by short lifespans with diminished late-age survival and fertility, similar to contemporary chimpanzees, and thence were subject to three changes. (1) A mating behavior change was established in which only young women reproduced, thereby rendering as effectively neutral female-specific late-onset fertility-diminishing mutations, which accumulated subsequently. (2) A lifespan increase was manifested adaptively, revealing the reproductive senescence phenotype encoded in late-onset fertility-diminishing mutation genotypes, which, heretofore, had been unexpressed in the shorter lifespan. (3) A social interaction change emerged exaptively, when older non-reproductive women exclusively started assisting in rearing grandchildren rather than giving birth to and caring for their own children, ultimately leading to menstrual cycle cessation. The changes associate in a one-to-one manner with existing, non-mutually exclusive hypotheses for the origin of human menopause. Evidence for each hypothesis and its associated change having occurred are reviewed, and the hypotheses are combined in a synthetic theory for the origin of human menopause. The new theory simultaneously addresses the main theoretical problem with each hypothesis and yields predictions for future testing.
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Affiliation(s)
| | - Rama S. Singh
- Department of Biology, Origins Institute, McMaster University, HamiltonON, Canada
| | - John Stone
- Department of Biology, Origins Institute, McMaster University, HamiltonON, Canada
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Sichimba F, Mooya H, Mesman J. Predicting Zambian Grandmothers' Sensitivity Toward Their Grandchildren. Int J Aging Hum Dev 2016; 85:185-203. [PMID: 27940904 DOI: 10.1177/0091415016680070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Whereas child care by grandmothers is widespread in the African cultural context, few studies have examined predictors of the quality of grandmaternal care in Africa. In the current study, we collected observational data to investigate predictors of the quality of grandmother-grandchild interactions in Zambia. Data were collected from 46 grandmothers and their 12 to 27-month-old infant grandchildren. The results revealed that grandmothers with fewer children and those who enjoyed the grandparenting tasks more were more sensitive in their interactions with their grandchildren. Unexpectedly, parenting beliefs favoring sensitive parenting predicted lower observed sensitivity in grandmothers. Further, grandmothers with a more individualistic cultural orientation were more intrusive toward their grandchildren. The results underscore the importance of time and emotional resources as predictors of sensitive parenting among grandmothers.
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Affiliation(s)
| | | | - Judi Mesman
- 2 Leiden University, Leiden, The Netherlands
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Kirchengast S, Putz B. Discriminative grandparental investment – the impact of grandchild’s gender and sociodemographic parameters. ANTHROPOLOGICAL REVIEW 2016. [DOI: 10.1515/anre-2016-0012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Homo sapiens is a typical cooperative breeder and grandparents are among the most important caregivers besides the mothers. Grandparental investment however differs markedly between maternal and paternal grandparents but also between grandmothers and grandfathers. From an evolutionary viewpoint this differential grandparental investment is mainly explained as a result of paternity uncertainty. On the other hand emotional support and child care help from grandparents may also be associated with sociocultural factors. The present study focused on the impact of grandchild’s gender, but also grandparental age and occupation on discriminative grandparental investment, i.e. solicitude, contact frequency and quality of relationship. 272 adults persons between the age 18 and 35 years (x= 23.5yrs; ±3.7) were enrolled in the study. Patterns of grandparental investment during childhood as well as quality of the grandparent- grandchild relationship were collected retrospectively using a 57 item questionnaire. As to be expected maternal grandmothers showed the highest contact frequency and the highest solicitude while -as to be expected - the paternal grandfather exhibited the lowest degree of investment. Grandparental investment was independent of grandparent category mainly influenced by residential distance. Grandchild’s gender and sociodemographic characteristics of the grandparents in contrast had a minor impact on grandparental caregiving and contact frequency. Contrary, grandchild’s gender was related significantly with the quality of relationship and emotional closeness.
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Sheppard P, Sear R. Do grandparents compete with or support their grandchildren? In Guatemala, paternal grandmothers may compete, and maternal grandmothers may cooperate. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160069. [PMID: 27152221 PMCID: PMC4852644 DOI: 10.1098/rsos.160069] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 03/17/2016] [Indexed: 06/05/2023]
Abstract
Previous research has found that the presence of grandparents, particularly grandmothers, is often positively associated with child survival. Little research has explored the potential mechanisms driving these associations. We use data from rural Guatemala to test whether contact with and direct investment (advice and financial) from grandparents is associated with child health, proxied by height. Our results demonstrate the complexity of family relationships and their influence on child health, suggesting that both cooperative and competitive relationships exist within the family. The clearest evidence we find for grandparental influence is that having a living paternal grandmother tends to be negatively associated with child height. By contrast, contact with maternal kin appears broadly to be beneficial for child height, although these relationships are weaker. These patterns are mirrored in maternal body mass index, suggesting grandparental influence acts partly through maternal health. These findings support the hypotheses that, under conditions of limited resources, family relationships may be competitive within the family lineage which shares the same resource base, but cooperative when there are few costs to cooperation. Finally, financial assistance from maternal grandfathers is positively correlated with infant length but negatively with the height of older children, perhaps because the receipt of financial support is an indication of need. The provision of advice shows no associations with child height.
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Subsistence-patterns, gender roles, effective temperature, and the evolutionary timing of a post reproductive life span. Med Hypotheses 2016; 89:48-57. [PMID: 26968909 DOI: 10.1016/j.mehy.2016.01.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 01/21/2016] [Accepted: 01/29/2016] [Indexed: 11/23/2022]
Abstract
Evolutionary anthropologists explain menopause and the start of a post reproductive lifespan (PRLS), as beneficiary for older women who can now help contribute to their children/grandchildren's wellbeing. This paper presents a new model with the aim to elucidate when, where, and for whom, such benefits may have arisen. In foraging societies, women contribute nutrients to their social groups/family units to a greater degree as overall effective temperatures (ETs) rise. Where the ET is favorable for women's contributions (ETs between 15 and 20), selection does lengthen the PRLS of women because women contribute sufficiently to enhance their own inclusive fitness. Paleo-environment records suggest that the climate necessary to encourage an increase PRLS occurred shortly after the younger dryad in emerging subtropical settings. Subsistence patterns and gender roles may have played a role in the evolution of PRLS in human females.
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30
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Does grandparental help mediate the relationship between kin presence and fertility? DEMOGRAPHIC RESEARCH 2016. [DOI: 10.4054/demres.2016.34.17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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31
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Kramer KL, Veile A, Otárola-Castillo E. Sibling Competition & Growth Tradeoffs. Biological vs. Statistical Significance. PLoS One 2016; 11:e0150126. [PMID: 26938742 PMCID: PMC4777386 DOI: 10.1371/journal.pone.0150126] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 02/09/2016] [Indexed: 11/18/2022] Open
Abstract
Early childhood growth has many downstream effects on future health and reproduction and is an important measure of offspring quality. While a tradeoff between family size and child growth outcomes is theoretically predicted in high-fertility societies, empirical evidence is mixed. This is often attributed to phenotypic variation in parental condition. However, inconsistent study results may also arise because family size confounds the potentially differential effects that older and younger siblings can have on young children's growth. Additionally, inconsistent results might reflect that the biological significance associated with different growth trajectories is poorly understood. This paper addresses these concerns by tracking children's monthly gains in height and weight from weaning to age five in a high fertility Maya community. We predict that: 1) as an aggregate measure family size will not have a major impact on child growth during the post weaning period; 2) competition from young siblings will negatively impact child growth during the post weaning period; 3) however because of their economic value, older siblings will have a negligible effect on young children's growth. Accounting for parental condition, we use linear mixed models to evaluate the effects that family size, younger and older siblings have on children's growth. Congruent with our expectations, it is younger siblings who have the most detrimental effect on children's growth. While we find statistical evidence of a quantity/quality tradeoff effect, the biological significance of these results is negligible in early childhood. Our findings help to resolve why quantity/quality studies have had inconsistent results by showing that sibling competition varies with sibling age composition, not just family size, and that biological significance is distinct from statistical significance.
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Affiliation(s)
- Karen L. Kramer
- Department of Anthropology, University of Utah, Salt Lake City, Utah 84112, United States of America
| | - Amanda Veile
- Department of Anthropology, Purdue University, West Lafayette, Indiana, United States of America
| | - Erik Otárola-Castillo
- Department of Anthropology, Purdue University, West Lafayette, Indiana, United States of America
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32
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Relatedness and investment in children in South Africa. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2015; 16:1-31. [PMID: 26189514 DOI: 10.1007/s12110-005-1005-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2004] [Revised: 11/04/2004] [Indexed: 10/23/2022]
Abstract
Investment in children is examined using a nationally representative sample of 11,211 black (African) households in South Africa. I randomly selected one child from each household in the sample and calculated the average genetic relatedness of the other household members to the focal child. Using multivariate statistical analysis to control for background variables such as age and sex of child, household size, and socioeconomic status, I examine whether the coefficient of relatedness predicts greater household expenditures on food, on health care, and on children's clothing. I also test whether relatedness is associated with health and schooling outcomes. The results are consistent with an inclusive fitness model: Households invest more in children who are more closely related. Two exceptions were found: in rural areas, genetic relatedness was negatively associated with money spent on food and on health care. Explanations for these results are discussed.
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Sear R. Kin and Child Survival in Rural Malawi : Are Matrilineal Kin Always Beneficial in a Matrilineal Society? HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2015; 19:277-93. [PMID: 26181618 DOI: 10.1007/s12110-008-9042-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This paper investigates the impact of kin on child survival in a matrilineal society in Malawi. Women usually live in close proximity to their matrilineal kin in this agricultural community, allowing opportunities for helping behavior between matrilineal relatives. However, there is little evidence that matrilineal kin are beneficial to children. On the contrary, child mortality rates appear to be higher in the presence of maternal grandmothers and maternal aunts. These effects are modified by the sex of child and resource ownership: female children and children in households where women, rather than men, own land suffer higher mortality rates in the presence of maternal kin. These modifiers suggest the detrimental effects of matrilineal kin may result from competition between such kin for resources. There are some positive effects of kin on child survival: the presence of elder siblings of both sexes is correlated with higher survival rates, and there is some weak evidence that paternal grandmothers may be beneficial to a child's survival chances. There is little evidence that any male kin, whether matrilineal or patrilineal, and including fathers, affect child mortality rates. This study highlights the importance of taking social and ecological context into account when investigating relationships between kin.
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Affiliation(s)
- Rebecca Sear
- Department of Social Policy, London School of Economics, Houghton St, London, WC2A 2AE, UK.
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Abstract
I present evidence that humans have evolved convergently to social insects with regard to a large suite of social, ecological, and reproductive phenotypes. Convergences between humans and social insects include: (1) groups with genetically and environmentally defined structures; (2) extensive divisions of labor; (3) specialization of a relatively restricted set of females for reproduction, with enhanced fertility; (4) extensive extramaternal care; (5) within-group food sharing; (6) generalized diets composed of high-nutrient-density food; (7) solicitous juveniles, but high rates of infanticide; (8) ecological dominance; (9) enhanced colonizing abilities; and (10) collective, cooperative decision-making. Most of these convergent phenotypic adaptations stem from reorganization of key life-history trade-offs due to behavioral, physiological, and life-historical specializations. Despite their extensive socioreproductive overlap with social insects, humans differ with regard to the central aspect of eusociality: reproductive division of labor. This difference may be underpinned by the high energetic costs of producing offspring with large brains.
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Affiliation(s)
- Bernard Crespi
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada, V5A 1S6,
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35
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36
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Wealth modifies relationships between kin and women's fertility in high-income countries. Behav Ecol 2014. [DOI: 10.1093/beheco/aru059] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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37
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Sims M, Rofail M. The experiences of grandparents who have limited or no contact with their grandchildren. J Aging Stud 2013; 27:377-86. [PMID: 24300058 DOI: 10.1016/j.jaging.2013.09.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 08/15/2013] [Accepted: 09/05/2013] [Indexed: 11/15/2022]
Abstract
PURPOSE OF THE STUDY The matrilineal advantage theory suggests that paternal grandparents are more at risk of having little or no contact with their grandchildren. However, there is significant family diversity within Australia and we wished to understand the experiences of a wide range of grandparents in order to determine if the matrilineal theory can be effectively used in practice to identify those grandparents most at risk for estrangement. DESIGN AND METHODS A convenience group of grandparents with little or no contact with grandchildren (n=38) told their stories in their own words using narratives obtained through interview or writing. RESULTS AND IMPLICATIONS We found that paternal grandparents, as per the matrilineal advantage theory, were more likely to be estranged from their grandchildren when their son divorced, particularly when he was not the resident parent or when he re-partnered. However, in contrast, we found that maternal grandparents who experienced conflict in their relationship with their daughter were also at risk for estrangement. This occurred even when grandparents had previously been highly involved in the lives of their grandchildren. Some estrangements appeared to result from a cultural bias towards the nuclear family form. We argue that practitioners need not only to expand their understanding of the risk categories for estrangement, they also need to actively support parents and grandparents in creating and maintaining wider family support networks in order to improve family resilience.
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Affiliation(s)
- Margaret Sims
- University of New England, Armidale, NSW 2351, Australia.
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Abstract
Human menopause is an unsolved evolutionary puzzle, and relationships among the factors that produced it remain understood poorly. Classic theory, involving a one-sex (female) model of human demography, suggests that genes imparting deleterious effects on post-reproductive survival will accumulate. Thus, a 'death barrier' should emerge beyond the maximum age for female reproduction. Under this scenario, few women would experience menopause (decreased fertility with continued survival) because few would survive much longer than they reproduced. However, no death barrier is observed in human populations. Subsequent theoretical research has shown that two-sex models, including male fertility at older ages, avoid the death barrier. Here we use a stochastic, two-sex computational model implemented by computer simulation to show how male mating preference for younger females could lead to the accumulation of mutations deleterious to female fertility and thus produce a menopausal period. Our model requires neither the initial assumption of a decline in older female fertility nor the effects of inclusive fitness through which older, non-reproducing women assist in the reproductive efforts of younger women. Our model helps to explain why such effects, observed in many societies, may be insufficient factors in elucidating the origin of menopause.
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Tanskanen AO. The Association between Grandmaternal Investment and Early Years Overweight in the UK. EVOLUTIONARY PSYCHOLOGY 2013. [DOI: 10.1177/147470491301100212] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Previous studies show that in many pre-modern and traditional populations the presence of a grandmother correlates with increased child survival rates, maybe as a result of improved child nutrition. Grandmaternal investment aimed at improving grandchildren's nutritional status in subsistence societies may have different outcomes in contemporary affluent societies. Using the British Millennium Cohort Study I investigate the association between maternal and paternal grandmothers' childcare and early years overweight in the UK. Results show that children who were cared for mainly by their grandmothers between the ages of 9 months and 3 years were more likely overweight at age 3 than children who were cared for by their parents. My results are in line with Pearce, Abbas, Ferguson, Graham, and Law (2010) , although they did not distinguish grandmothers by lineage. Grandmothers may influence children's nutritional status in contemporary societies, but as with many evolved behavioral strategies the outcome may be no longer beneficial.
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Affiliation(s)
- Antti O. Tanskanen
- Department of Social Research, University of Helsinki, Helsinki, Finland
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Willführ KP, Gagnon A. Are stepparents always evil? Parental death, remarriage, and child survival in demographically saturated Krummhörn (1720-1859) and expanding Québec (1670-1750). BIODEMOGRAPHY AND SOCIAL BIOLOGY 2013; 59:191-211. [PMID: 24215259 DOI: 10.1080/19485565.2013.833803] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Parental death precipitates a cascade of events leading to more or less detrimental exposures, from the sudden and dramatic interruption of parental care to cohabitation with stepparents and siblings in a recomposed family. This article compares the effect of early parental loss on child survival in the past in the Krummhörn region of East Frisia (Germany) and among the French Canadian settlers of the Saint Lawrence Valley (Québec, Canada). The Krummhörn region was characterized by a saturated habitat, while the opportunities for establishing a new family were virtually unlimited for the French Canadian settlers. Early parental loss had quite different consequences in these dissimilar environments. Event history analyses with time-varying specification of family structure are used on a sample of 7,077 boys and 6,906 girls born between 1720 and 1859 in the Krummhörn region and 31,490 boys and 33,109 girls whose parents married between 1670 and 1750 in Québec. Results indicate that in both populations, parental loss is associated with increased infant and child mortality. Maternal loss has a universal and consistent effect for both sexes, while the impact of paternal loss is less easy to establish and interpret. On the other hand, the effect of the remarriage of the surviving spouse is population-specific: the mother's remarriage has no effect in Krummhörn, while it is beneficial in Québec. In contrast, the father's remarriage in Krummhörn dramatically reduces the survival chances of the children born from his former marriage, while such an effect is not seen for Québec. These population-specific effects appear to be driven by the availability of resources and call into question the universality of the "Cinderella" effect.
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Affiliation(s)
- Kai P Willführ
- a Max Planck Institute for Demographic Research , Rostock , Germany
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41
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Labrie F, Labrie C. DHEA and intracrinology at menopause, a positive choice for evolution of the human species. Climacteric 2012; 16:205-13. [DOI: 10.3109/13697137.2012.733983] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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42
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Alternatives to the grandmother hypothesis: a meta-analysis of the association between grandparental and grandchild survival in patrilineal populations. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2012; 22:201-22. [PMID: 22388808 DOI: 10.1007/s12110-011-9114-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We conducted a meta-analysis of 17 studies that tested for an association between grandparental survival and grandchild survival in patrilineal populations. Using two different methodologies, we found that the survival of the maternal grandmother and grandfather, but not the paternal grandmother and grandfather, was associated with decreased grandoffspring mortality. These results are consistent with the findings of psychological studies in developed countries (Coall and Hertwig Behavioral and Brain Sciences 33:1-59, 2010). When tested against the predictions of five hypotheses (confidence of paternity; grandmothering, kin proximity, grandparental senescence, and local resource competition), our meta-analysis results are most in line with the local resource competition hypothesis. In patrilineal and predominantly patrilocal societies, the grandparents who are most likely to live with the grandchildren have a less beneficial association than those who do not. We consider the extent to which these results may be influenced by the methodological limitations of the source studies, including the use of retrospective designs and inadequate controls for confounding variables such as wealth.
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Seki M. Intra-individual conflicts between autosomal and X-linked altruistic genes: evolutionary perspectives of sex-specific grandmothering. J Theor Biol 2012; 304:273-85. [PMID: 22498803 DOI: 10.1016/j.jtbi.2012.03.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 03/22/2012] [Accepted: 03/23/2012] [Indexed: 11/18/2022]
Abstract
Alloparental care by females toward their grandoffspring can evolve by kin selection. Previous theoretical studies predicted that selection favors autosomal and X-chromosomal genes, causing altruism toward maternal grandoffspring and paternal granddaughters, respectively, and two corresponding types of biased grandparental investment are suggested by empirical studies on human populations. Using discrete-time two-locus-two-allele models, I examined a possible conflict between the autosomal and the X-chromosomal altruistic genes over the carrier female's time and resources. This conflict is expected to occur when each grandmother has access to only maternal or paternal grandchildren as a result of her residence situation. The conditions under which each or both kinds of altruistic genes evolve (against non-altruistic genes) mainly represent the conflicting relationship between the autosomal and X-chromosomal altruistic genes. In addition, depending on the settings, the models exhibit bistable or periodic behaviors, and one type of gene can be considered parasitic in the latter behavior. On the whole, the results suggest that the X-chromosomal altruistic genes rather than the autosomal ones exhibit more difficulty increasing or fixing with this kind of conflict.
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Affiliation(s)
- Motohide Seki
- Department of Biological Sciences, The University of Tokyo, Hongo 7-3-1, Tokyo 113-0033, Japan.
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44
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Kachel AF, Premo LS. Disentangling the Evolution of Early and Late Life History Traits in Humans. Evol Biol 2012. [DOI: 10.1007/s11692-012-9169-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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45
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Pavard S, Branger F. Effect of maternal and grandmaternal care on population dynamics and human life-history evolution: a matrix projection model. Theor Popul Biol 2012; 82:364-76. [PMID: 22326750 DOI: 10.1016/j.tpb.2012.01.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 01/23/2012] [Accepted: 01/23/2012] [Indexed: 11/29/2022]
Abstract
We present a matrix population model for a single-sex human population comprising non-orphan daughters (whose mothers are alive) and orphan daughters (whose mothers are dead). Orphans suffer higher mortality than non-orphans, which simulates the need for daughters to receive maternal care in order to survive. The way that maternal care affects population dynamics and life-history evolution is then analysed for demographic regimes that encompass large ranges of daughter survival, mother survival and fertility. We provide stable age-distributions of orphans and non-orphans for each regime and perform sensitivity analyses on daughter survival, adult survival and fertility. The results show that natural selection will favour (i) faster daughter independence from maternal care, (ii) higher adult survival at all ages, and (iii) early reproduction to the detriment of late reproduction. We then build scenarios concerning the coevolution of daughter survival and maternal care with adult survival and fertility. We also incorporate grandmaternal care into the model. We show that (i) the acute altriciality of human babies, (ii) the increased maternal care resulting from emergence of complex sociality and (iii) the role played by grandmothers in caring for granddaughters may have led to the emergence of specific human life-history traits: a short reproductive period characterised by a reproductive senescence and menopause, as well as an extended lifespan characterised by a post-reproductive life.
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Affiliation(s)
- Samuel Pavard
- UMR 7206 Eco-Anthropologie, Equipe Génétique desPopulations Humaines, Muséum National d'Histoire Naturelle, Paris, France.
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Abstract
In animals that breed cooperatively, adult individuals will sometimes delay reproduction to act as helpers at the nest who raise young that are not their genetic offspring. It has been proposed that humans are also a cooperatively breeding species because older daughters, grandmothers, and other kin and nonkin may provide significant childcare. Through a prospective cohort study of children's (n = 1,700) growth and survival in the Dogon of Mali, I show that cooperative breeding theory is a poor fit to the family dynamics of this population. Rather than helping each other, siblings competed for resources, producing a tradeoff between the number of maternal siblings and growth and survival. It did not take a village to raise a child; children fared the same in nuclear as in extended families. Of critical importance was the degree of polygyny, which created conflicts associated with asymmetries in genetic relatedness. The risk of death was higher and the rate of growth was slower in polygynous than monogamous families. The hazard of death for Dogon children was twofold higher if the resident paternal grandmother was alive rather than dead. This finding may reflect the frailty of elderly grandmothers who become net consumers rather than net producers in this resource-poor society. Mothers were of overwhelming importance for child survival and could not be substituted by any category of kin or nonkin. The idea of cooperative breeding taken from animal studies is a poor fit to the complexity and diversity of kin interactions in humans.
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Fox M, Johow J, Knapp LA. The selfish grandma gene: the roles of the x-chromosome and paternity uncertainty in the evolution of grandmothering behavior and longevity. INTERNATIONAL JOURNAL OF EVOLUTIONARY BIOLOGY 2011; 2011:165919. [PMID: 21716697 PMCID: PMC3118636 DOI: 10.4061/2011/165919] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 12/07/2010] [Accepted: 01/18/2011] [Indexed: 11/20/2022]
Abstract
When considering inclusive fitness, it is expected that individuals will provide more care towards those with whom they are more closely related. Thus, if a selfish X-linked genetic element influenced care giving, we would expect care giving to vary with X-relatedness. Recent studies have shown that X-chromosome inheritance patterns may influence selection of traits affecting behavior and life-history. Sexually antagonistic (SA) zygotic drive could encourage individuals to help those with whom they are more likely to share genetic material at the expense of other relatives. We reanalyze previously reported data in light of this new idea. We also evaluate the effects of paternity uncertainty on SA-zygotic drive. Our evidence suggests that human paternal discrepancy is relatively low. Using published models, we find the effects of paternal discrepancy do not override opportunity for selection based on X-relatedness. Based on these results, longevity and grandmothering behaviors, including favoritism, may be more heavily influenced by selection on the X-chromosome than by paternity uncertainty.
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Affiliation(s)
- Molly Fox
- Department of Biological Anthropology, University of Cambridge, Pembroke Street, Cambridge CB2 3QY, UK
| | - Johannes Johow
- Zentrum für Philosophie und Grundlagen der Wissenschaft, Universität Giessen, Otto-Behaghel-Straße 10 C, 35394 Giessen, Germany
| | - Leslie A. Knapp
- Department of Biological Anthropology, University of Cambridge, Pembroke Street, Cambridge CB2 3QY, UK
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Kachel AF, Premo LS, Hublin JJ. Grandmothering and natural selection. Proc Biol Sci 2011; 278:384-91. [PMID: 20739319 PMCID: PMC3013409 DOI: 10.1098/rspb.2010.1247] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 08/05/2010] [Indexed: 11/12/2022] Open
Abstract
Humans are unique among primates in that women regularly outlive their reproductive period by decades. The grandmother hypothesis proposes that natural selection increased the length of the human post-menopausal period-and, thus, extended longevity-as a result of the inclusive fitness benefits of grandmothering. However, it has yet to be demonstrated that the inclusive fitness benefits associated with grandmothering are large enough to warrant this explanation. Here, we show that the inclusive fitness benefits are too small to affect the evolution of longevity under a wide range of conditions in simulated populations. This is due in large part to the relatively weak selection that applies to women near or beyond the end of their reproductive period. However, we find that grandmothers can facilitate the evolution of a shorter reproductive period when their help decreases the weaning age of their matrilineal grandchildren. Because selection favours a shorter reproductive period in the presence of shorter interbirth intervals, this finding holds true for any form of allocare that helps mothers resume cycling more quickly. We conclude that while grandmothering is unlikely to explain human-like longevity, allocare could have played an important role in shaping other unique aspects of human life history, such as a later age at first birth and a shorter female reproductive period.
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Affiliation(s)
- A Friederike Kachel
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
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Danielsbacka M, Tanskanen AO, Jokela M, Rotkirch A. Grandparental child care in Europe: evidence for preferential investment in more certain kin. EVOLUTIONARY PSYCHOLOGY 2011; 9:3-24. [PMID: 22947949 PMCID: PMC10481010 DOI: 10.1177/147470491100900102] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Accepted: 12/31/2010] [Indexed: 07/30/2024] Open
Abstract
Theories of kin selection and parental investment predict stronger investment in children and grandchildren by women and maternal kin. Due to paternity uncertainty, parental and grandparental investments along paternal lineages are based on less certain genetic relatedness with the children and grandchildren. Additionally, the hypothesis of preferential investment (Laham, Gonsalkorale, and von Hippel, 2005) predicts investment to vary according to available investment options. Two previous studies have tested this hypothesis with small samples and conflicting results. Using the second wave of the large and multinational Survey of Health, Ageing and Retirement in Europe (SHARE), collected in 2006-07, we study the preferential investment hypothesis in contemporary Europe based on self-reported grandparental provision of child care. We predict that 1) maternal grandmothers provide most care for their grandchildren, followed by maternal grandfathers, paternal grandmothers and last by paternal grandfathers; 2) maternal grandfathers and paternal grandmothers provide equal amounts of care when the latter do not have grandchildren via a daughter; 3) women who have grandchildren via both a daughter and a son will look after the children of the daughter more; and 4) men who have grandchildren via both a daughter and a son will look after the children of the daughter more. Results support all four hypotheses and provide evidence for the continuing effects of paternity uncertainty in contemporary kin behavior.
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Affiliation(s)
- Mirkka Danielsbacka
- Department of Philosophy, History, Culture and Art Studies, University of Helsinki, Helsinki, Finland.
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Sear R, Coall D. How much does family matter? Cooperative breeding and the demographic transition. POPULATION AND DEVELOPMENT REVIEW 2011; 37:81-112. [PMID: 21280366 DOI: 10.1111/j.1728-4457.2011.00379.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
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