Allomaternal Investments and Child Outcomes in the United Kingdom
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Allomaternal Investments and Child Outcomes in the United Kingdom Emily Hazuki Emmott Doctor of Philosophy Department of Anthropology University College London 2014 p. 1 Declaration I, Emily Hazuki Emmott, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. Emily H. Emmott p. 2 Abstract Due to the fact that human mothers often have multiple, vulnerable offspring with long periods of dependency, it is argued that mothers need assistance from allomothers to successfully provide and care for their children. Cross-cultural observations and quantitative research converge on support for the idea that mothers in high fertility, high mortality populations need assistance from other individuals for successful childrearing. It is also clear within the literature that there is variation across populations in terms of who matters: who provides the help, how they help, and how much impact they have on childrearing. The current thesis extends from previous studies by exploring the effects of allomothers on childrearing in a contemporary developed context: With economic development and the demographic transition, questions arise regarding the importance of allomothers for successful childrearing, and whether humans in these settings still operate as cooperative breeders. This thesis specifically focuses on quantitatively investigating the effects of fathers, stepfathers and grandparents on child development in the UK. First, using the Avon Longitudinal Study of Parents and Children, I investigate how direct investments from fathers and stepfathers affect multiple child outcomes. Second, using the UK Millennium Cohort Study, I investigate how direct and indirect investments from maternal and paternal grandparents affect parental investment levels, as well as multiple child outcomes. Taken together, my findings suggest that allomothers do indeed impact child development in the UK. However, the important allomothers seem to be those within the nuclear household. This is in contrast with many high-fertility, high mortality populations where grandmothers, especially maternal grandmothers, are often the most important allomothers regarding child survival, and fathers less so. Within its limits, the current thesis highlights who matters for childrearing in the UK today. p. 3 Table of Contents Abstract ------------------------------------------------------------------------------------------------------ 3 Table of Contents ----------------------------------------------------------------------------------------- 4 List of Tables ----------------------------------------------------------------------------------------------- 9 List of Figures ---------------------------------------------------------------------------------------------- 11 Glossary----------------------------------------------------------------------------------------------------- 14 Acknowledgements-------------------------------------------------------------------------------------- 15 Chapter 1: Introduction ----------------------------------------------------------------------------- 17 1.1 Overview of the Project ------------------------------------------------------------------------ 17 1.2 The Context Surrounding This Project ------------------------------------------------------ 18 1.2.1 The Need for Allomothers for Successful Childrearing in Humans ----------------- 18 1.2.2 Patterns of Allomaternal Care across Cultures ---------------------------------------- 21 1.2.3 Defining Cooperative Breeding in Humans -------------------------------------------- 30 1.3 Theoretical Background of the Thesis ------------------------------------------------------- 33 1.3.1 Human Behavioural Ecology ------------------------------------------------------------- 33 1.3.2 Defining Investments into Children ---------------------------------------------------- 35 1.3.3 Why Invest in Children? ----------------------------------------------------------------- 40 1.4 Allomothers and their Effects on Children within Subsistence and Developing Populations ----------------------------------------------------------------------------------------- 45 1.4.1 Allomaternal Effects on Child Fitness -------------------------------------------------- 45 1.4.2 Variations in Who Matters for Children ---------------------------------------------- 48 1.5 Investigating Allomaternal Effects in Contemporary Developed Populations --------- 51 1.5.1 Overview: Investigating Allomaternal Efffects from an HBE Perspective ---------- 51 1.5.2 Application of HBE in Contemporary Developed Populations ---------------------- 51 1.5.3 The Measures of Interest in the Current Thesis --------------------------------------- 54 1.6 Aims of the Thesis: Investigating Allomaternal Effects in the UK ----------------------- 56 1.6.1 Why Study Allomothering in the UK? -------------------------------------------------- 56 1.6.2 The Allomaternal Context in the UK --------------------------------------------------- 56 p. 4 1.6.3 The Research Approach of the Current Project --------------------------------------- 58 1.7 Outline of the Thesis ------------------------------------------------------------------------- 60 Part 1: Fathers and Stepfathers ----------------------------------------------------------------------- 61 Chapter 2: Introducing Part 1 and the ALSPAC Dataset ------------------------------------- 62 2.1 Aims of Part 1 ----------------------------------------------------------------------------------- 62 2.2 ALSPAC Dataset Description ---------------------------------------------------------------- 63 2.3 Key Variables of ALSPAC for Part 1 ---------------------------------------------------------- 63 2.3.1 ALSPAC Parenting Scores --------------------------------------------------------------- 64 2.3.2 ALSPAC Child Outcomes ---------------------------------------------------------------- 71 2.4 Overview of the Research Questions in Part 1 --------------------------------------------- 78 Chapter 3: Father Effects on Multiple Child Outcomes ------------------------------------- 79 3.1 Introduction to Chapter 3 --------------------------------------------------------------------- 79 3.1.1 Fathers as Allomothers in Contemporary Developed Populations ------------------ 79 3.1.2 Father Effects on Child Development in Contemporary Developed Populations 80 3.1.3 Variations in the Effects of Paternal Investment -------------------------------------- 83 3.1.3 Objectives of Chapter 3 ------------------------------------------------------------------- 85 3.2. Analysis Methods of Chapter 3 ------------------------------------------------------------- 86 3.2.1 Sample Selection ------------------------------------------------------------------------- 86 3.2.2 Variables ---------------------------------------------------------------------------------- 86 3.2.3 Analyses ------------------------------------------------------------------------------------ 91 3.3 Results of Chapter 3 -------------------------------------------------------------------------- 96 3.4 Discussion of Chapter 3 ---------------------------------------------------------------------- 100 3.4.1 Main Findings of Chapter 3 ------------------------------------------------------------- 100 3.4.2 Limitations of the Current Analyses -------------------------------------------------- 102 3.4.3 Conclusions: The Importance of Fathers as Allomothers in the UK -------------- 102 Chapter 4:Stepfather Effects on Multiple Child Outcomes ---------------------------- 104 4.1 Introduction to Chapter 4 ------------------------------------------------------------------- 104 p. 5 4.1.1 Stepfathers as Allomothers in Contemporary Developed Populations ------------ 104 4.1.2 Stepfather Effects on Child Development in Contemporary Developed Populations ------------------------------------------------------------------------------------- 105 4.1.3 Objectives of Chapter 4------------------------------------------------------------------ 109 4.2 Analysis Methods of Chapter 4 -------------------------------------------------------------- 111 4.2.1 Sample Selection -------------------------------------------------------------------------- 111 4.2.2 Variables ---------------------------------------------------------------------------------- 112 4.2.3 Analyses ----------------------------------------------------------------------------------- 116 4.3 Results of Chapter 4 -------------------------------------------------------------------------- 117 4.3.1 Mother and Partner’s Investment Scores --------------------------------------------- 117 4.3.2 Main Analyses ---------------------------------------------------------------------------- 118 4.4.1 Main Findings of Chapter 4 ------------------------------------------------------------- 123 4.4.2 Limitations of the Current Analyses -------------------------------------------------- 126 4.4.3 Conclusions: The Importance of Stepfathers as Allomothers in the UK --------- 128 Part 2: Grandparents ----------------------------------------------------------------------------------- 130 Chapter 5: Introducing Part 2 and the MCS Dataset ---------------------------------------- 131 5.1 Aims of Part 2 ---------------------------------------------------------------------------------- 131 5.1.1 Theoretical Background: The Determinants of Grandparental Effects on Child Outcomes ---------------------------------------------------------------------------------------