Social structure and knowledge sharing networks in hunter-gatherers A case study on the plant knowledge of the Mbendjele BaYaka Pygmies Gül Deniz Salalı A dissertation submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy Department of Anthropology University College London February 2017 I, Gül Deniz Salalı, 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 work. 2 Abstract Hunters and gatherers occupied 95% of the human history. Despite the forces of globalization, current-day hunter-gatherers can shed light on how we adapted to different environments and generated complex cultural traits. Their changing ways of life, on the other hand, may let us understand cultural change. In this thesis, I explore the cultural evolution of plant knowledge in an extant hunter-gatherer population, the Mbendjele BaYaka Pygmies from the Northern Republic of Congo. In Chapter 4, I show that the Mbendjele use wild plants for various reasons from treating digestive system disorders to punishing norm violators. In Chapter 5, I investigate whether there are adaptive benefits to the use of certain medicinal plants and explore the common uses of medicinal plants across different Pygmy populations and great apes. I also explore the known bioactive compounds, and test the effects of mothers’ use of certain medicinal plants on their children’s body- mass-index. In Chapter 6, I investigate how the Mbendjele have evolved such a rich plant use repertoire by exploring sharing of medicinal and non-medicinal plant knowledge with respect to features of social structure. I argue that the long-term pair bonds, marital ties and cooperative breeding have allowed the Mbendjele to combine and accumulate rich medicinal plant uses. Additionally, co-residence of multiple families provides a context for the sharing and accumulation of plant uses that concern cooperative foraging and social norms. In Chapter 7, I explore the socioeconomic transitions in the Mbendjele that live in a logging town and examine how plant knowledge declines with their changing life-style. I argue that change in subsistence activities, emerging inequalities and decreased mobility hinder the transmission of traditional knowledge. Nevertheless, I argue that adoption of new cultural traits may be inevitable and beneficial for the resilience of modern day hunter-gatherers. 3 Contents Chapter 1: Introduction ................................................................................................ 18 1.1 Evolutionary approaches to culture .................................................................... 18 1.1.1 Is culture adaptive? .................................................................................... 21 1.2 Social structure, human life history traits and cultural transmission ................. 22 1.2.1 Human social structure & life-history ........................................................ 22 1.2.2 Effects on cultural transmission ................................................................. 26 1.3 Why study culture in hunter-gatherers? ............................................................. 27 1.3.1 Current day hunter-gatherers...................................................................... 28 1.3.2 Hunter-gatherer social structure ................................................................. 29 1.3.3 Plant knowledge in hunter-gatherers as a case study ................................. 34 1.4 Changes in social structure and cultural transmission ....................................... 34 1.5 Aims and overview of the thesis ........................................................................ 35 Chapter 2: The Mbendjele BaYaka ............................................................................. 37 2.1 Overview of the Study population ..................................................................... 37 2.2 Central African Pygmies and their languages .................................................... 39 2.3 Pygmy origins .................................................................................................... 42 2.4 Mbendjele BaYaka ............................................................................................. 44 2.4.1 Mbendjele subsistence ............................................................................... 44 2.4.2 Mbendjele social structure ......................................................................... 49 2.4.3 Mbendjele - farmer relations ...................................................................... 53 2.4.4 Mbendjele Culture ...................................................................................... 55 4 Chapter 3: Fieldwork and Data Collection .................................................................. 62 3.1 2013 Fieldwork .................................................................................................. 63 3.1.1 Longa ......................................................................................................... 67 3.1.2 Enoko ......................................................................................................... 71 3.1.3 Mbaya ........................................................................................................ 71 3.1.4 Daily routine and relations with the Mbendjele ......................................... 72 3.2 2014 Fieldwork .................................................................................................. 76 3.2.1 Longa ......................................................................................................... 79 3.2.2 Ibamba ........................................................................................................ 80 3.2.3 Town camps: Bolobo and Sembola............................................................ 82 3.2.4 Masia .......................................................................................................... 84 3.2.5 Minganga ................................................................................................... 88 3.3 Data Collection .................................................................................................. 89 3.3.1 Ethical Approval and Informed Consents .................................................. 89 3.3.2 Genealogies & Kinship .............................................................................. 90 3.3.3 Anthropometrics......................................................................................... 93 3.3.4 Aging .......................................................................................................... 94 3.3.5 Interviews ................................................................................................... 96 3.3.6 Behavioural Games .................................................................................... 98 3.3.7 Filming ..................................................................................................... 100 Chapter 4: Plant uses in the Mbendjele BaYaka ........................................................ 101 4.1 Introduction ...................................................................................................... 101 4.1.1 Plant use research in Central African Pygmies ........................................ 101 5 4.1.2 Importance of plant use ............................................................................ 102 4.2 Methods ............................................................................................................ 103 4.2.1 Initial plant list ......................................................................................... 103 4.2.2 Data collection ......................................................................................... 104 4.2.3 Plant identification ................................................................................... 105 4.2.4 Categorization of plant uses ..................................................................... 105 4.2.5 Preparation methods ................................................................................. 107 4.3 Results .............................................................................................................. 110 4.3.1 Majority of plant uses concerned medicinal purposes ............................. 110 4.3.2 Some plants were used by a large number of people but others not ........ 112 4.3.3 Some plants had a larger consensus on their use purpose ........................ 112 4.3.4 Women and men differed in their plant use only in a few cases .............. 116 4.3.5 Participants who resided or were born in the town camp reported using plants for medicine less frequently .............................................................................. 118 4.3.6 Poisonous plants were used to detect cheaters ......................................... 120 4.4 Discussion ........................................................................................................ 121 4.4.1 Medicinal uses of plants and their implications ....................................... 122 4.4.2 Plant uses of men and women and sex-specific knowledge sharing ........ 124 4.4.3 Market integration and plant uses across the Mbendjele camps .............. 125 4.4.4 Conclusion ............................................................................................... 125 Chapter 5: Is medicinal plant use adaptive? Cross cultural and cross