On Trade-offs and Communal Breeding The Behavioural Ecology of Agta Foragers Abigail Emma Page A dissertation submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy of University College London Department of Anthropology University College London March 2016 I, Abigail E. Page 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. 2 Abstract Time is finite and no organism can avoid the allocation dilemma that this necessarily entails. A quintessential trade-off is that between parental investment and reproduction, otherwise known as the quality-quantity trade-off. However, humans may be exceptional among apes given our high quantity production of high quality offspring. This success has been argued only to be possible by breeding communally. In this thesis I explore questions surrounding trade-offs, communal breeding and their fitness consequences in a small-scale foraging society, the Agta. The first analysis examines the composition of Agta childcare using an innovative form of data collection to maximise sample sizes, previously a major limitation in hunter-gatherer research. The Agta, like many small-scale societies are prolific communal breeders. However, contra previous conclusions, juveniles and non-kin appeared to provide more allocare than grandmothers. Interactions with non-kin were associated with significant decreases in maternal workload, while interactions with siblings and grandmothers were not. The next analysis explores why both kin and non-kin behave cooperatively, finding support for kin selection among close kin and reciprocity for distant kin and non-kin allocare. Communal breeding appears to be an important mechanism to ensure enough childcare was received in the absence of other strategies to counter shortfalls in household energy budgets. The next analysis asks, what are the fitness consequences of maternal social networks and allocare? Mothers’ network centrality positively correlated with non-kin allocare as well as reproductive success, revealing the adaptive value of communal breeding. These results highlight the optimising nature of hunter-gatherer cooperation and life history strategies. 3 Acknowledgements I am, of course, completely indebted to my supervisor Andrea Migliano for seeing my potential from the start and working tirelessly with me to reach it. Also, for putting emoticons in feedback, which always made my day . She has provided invaluable advice, insight and guidance as well as being a great friend. Ruth Mace, as my secondary supervisor, has also provided me with excellent advice and critique, which helped built my work into what it is here. None of this would have been possible without the Agta, particularly all the children I got to know so well. I thank them unreservedly for having the patience to let me follow them around, measure them, and prick their fingers. Their understanding and acceptance is impressive. Particularly I would like to thank all the Agta mothers and girls for their care and acceptance and to Marinel and Jollibee for just being awesome. Of course, I was completely reliant on the advice, organisation and translation of our team of research assistants; Ata Christie, Gurly and Amay Crumpez and Imay Crumpez. Their Filipino spirit always made life fun and dynamic, as did the karaoke parties. I am very thankful to the local government in Palanan for allowing us to work with the Agta, and in particular to the Rural Health Unit and Palanan Station Hospital for working with me to organise the testing and treatment for over 400 Agta. It was hard, I didn’t think it would be possible, but it was and thanks to the team I feel that we accomplished something to help, however tiny. I was not alone in the field, and thanks to the hard work of Mark Dyble, Sylvain Viguier and Daniel Smith we were able to collect such a wealth of data on all aspects of life. I particularly thank Mark for all the debates that livened up the evenings. All this research was made possible by funding from the Leverhulme Trust as part of the Hunter-Gatherer Resilience Project led by Andrea Migliano, as well as Ruth Mace, Mark Thomas and Jerome Lewis. The rest of the hunter-gatherer team – Deniz Salali, Nik Chaudhary, James Thompson, Janis Strods and Lucio Vinicius – have offered invaluable guidance on the structure of data collection, research questions, as well as the final product. Many people have offered critique and feedback on the different chapters and my thanks goes out to Matt Thomas, Sarah Myers, Heidi Colleran, Emily Emmott as well as all members of the Human Evolutionary 4 Ecology group at UCL and members of the Evolutionary Demography Group at LSHTM for letting me gate-crash and present my work in its infancy. Ultimately, I am unbelievably thankful to Wallace Hobbes (AKA Sylvain Viguier) who is literally the cleverest person I know, and without whom I would not have made it this far. His maths and coding lessons and patient understanding have opened up a new world for me. Special thanks also to Helen Cassidy who is always loving and makes me want to be better. My family have remained patient and caring even when I disappear to stare at a computer; they are the best and I am proud of them. 5 Contents ABSTRACT ............................................................................................................................................... 3 ACKNOWLEDGEMENTS ....................................................................................................................... 4 CONTENTS ............................................................................................................................................... 6 1 INTRODUCTIONS 1.1 WHO ARE THE HUNTER-GATHERERS? ............................................................................................. 13 1.2 THEORETICAL APPROACHES .............................................................................................................. 15 1.3 HUMAN LIFE HISTORY TRAITS AND COOPERATIVE BREEDING ..................................................... 19 1.4 HYPOTHESES AND OBJECTIVES .......................................................................................................... 21 1.5 OVERVIEW OF THESIS STRUCTURE ................................................................................................... 21 2 THE AGTA: RESILIENT FORAGERS UNDER TRANSITION? .......................................... 23 2.1 DEMOGRAPHICS ................................................................................................................................... 26 2.2 KINSHIP AND RESIDENCE PATTERNS ............................................................................................... 32 2.3 CAMPS AND THEIR MOBILITY ............................................................................................................. 33 2.4 SUBSISTENCE AND DIET ..................................................................................................................... 36 2.5 WEALTH, CAMP PERMANENCE, FOOD STORAGE AND SECURITY .................................................. 43 2.6 TRANSITION VERSUS RESILIENCE ...................................................................................................... 46 2.7 CONCLUSIONS ....................................................................................................................................... 49 3 RISK AND THE EVOLUTION OF COOPERATIVE CHILDCARE....................................... 50 3.1 COOPERATIVE BREEDING: ITS DEFINITIONS AND QUESTIONS ...................................................... 50 3.2 WHY BREED COMMUNALLY? THEORETICAL PERSPECTIVES ........................................................ 53 3.3 ANTHROPOLOGICAL LITERATURE ..................................................................................................... 64 3.4 FLEXIBILITY, VARIABILITY AND RISK AVOIDANCE .......................................................................... 73 3.5 SUMMARY .............................................................................................................................................. 75 4 METHODOLOGICAL APPROACH AND DATA COLLECTION .......................................... 77 4.1 HUNTER-GATHERER PROJECT .......................................................................................................... 77 4.2 DATA COLLECTION............................................................................................................................... 78 4.3 MOTES ................................................................................................................................................... 84 4.4 FOCAL FOLLOWS AND CHILDCARE..................................................................................................... 90 4.5 AGING .................................................................................................................................................... 91 4.6 HEALTH SURVEY .................................................................................................................................. 95 4.7 STATISTICAL ANALYSIS ................................................................................................................... 100 5 PROXIMITY AS A MEASURE OF ALLOCARE? ..................................................................107 6 5.1 WHAT IS ALLOCARE AND WHY IS PROXIMITY