Conflict within and between social groups is a conspicuous feature of cooperative animal societies. Theoretical and empirical research aims to understand the role of within- and between-group conflict in the evolution of cooperative behaviour, but these forms of conflict are rarely studied together. Eviction as a means of within-group conflict resolution can have important implications for the individuals involved, and the wider population through effects on dispersal, gene flow, and population structure. Intergroup conflict, although prevalent in many social species, is relatively understudied outside of humans and chimpanzees, but could play an important role in the evolution of cooperative behaviours. However, currently there is a lack of understanding of the causes and consequences of within- and between-group conflict to be able to draw conclusions on theoretical links to their role in social evolution. In this thesis, I use a wild population of banded mongooses, Mungos mungo, to investigate the causes and consequences of eviction and intergroup conflict in a highly cooperative species. First, I show that eviction in banded mongooses is triggered by reproductive competition in both sexes (Chapter 2). Second, I find that, once the decision to evict has been made, younger females and those older, more closely related females are preferentially evicted (Chapter 3). This surprising result is explained by a theoretical model which shows that, where individuals are capable of resisting eviction, the usual prediction of positive kin discrimination can be reversed. Third, I show that eviction has demographic effects, with consequences for group size and recruitment (Chapter 4). Finally, I show that intergroup conflict is stimulated by intensified resource competition, and that the consequences of intergroup conflict can have measureable costs to both individuals and groups in the long- and short-term (Chapter 5). This work shows that the means of resolving within-group conflict at an individual level can resonate to affect demography and dynamics at higher levels, and that the nature and intensity of intergroup conflict has the potential to influence patterns of cooperation and conflict within groups. I suggest that within- and between-group conflict may often be intimately linked, and that recognising this link could help to advance our conceptual understanding of their role in the evolution of cooperative behaviour.

Organisms are frequently faced with uncertainty regarding how best to exploit vital resources, and may benefit from collecting information about their distribution through space and time. However, the ways in which competition over resources might systematically facilitate or constrain an individual's ability to use information has been largely overlooked. In this thesis, I develop a conceptual framework for considering how the distribution of limited resources might underpin interdependencies between competition and information use. I focus on the evolutionary ecology of relationships between social dominance and social information use. I begin with an observational study of wild chacma baboons (Papio ursinus) suggesting that, when resources can be monopolised, individuals with low competitive ability are limited in their ability to use social information. Building on these findings, I then develop a general model exploring selection on social information use in a competitive context across three axes of 'resource ecology' (scarcity, depletion rate, monopolisability). This study makes predictions regarding the resource conditions under which competitive ability might constrain social information use, and the potential importance of social information use in the evolution of social dominance. I go on to test these predictions in chacma baboons using a field experiment. This experiment also explores whether the predictability of resource distribution might facilitate the decoupling of social information use from the competitive context in which it was collected. Taken together, these findings provide general insights into the combinations of ecological conditions and behavioural mechanisms that should underpin the benefits of social dominance. I end by building a simple population matrix model to study social dominance using an eco-evolutionary approach, in which feedback loops between ecological and evolutionary processes are considered. By modelling relationships between dominance rank and survival, reproduction, inheritance, and development, I am able to derive estimates of long-term fitness associated with dominance. Using these estimates, I generate predictions regarding how dominance hierarchies should impact the dynamics of group stability, viability, and fission.

Human culture has been proposed to uniquely exhibit a ‘ratchet effect’, with beneficial modifications being made to cultural traits over many generations. This is widely thought to have allowed an accumulation of technology and knowledge over time, and to be of central importance to the remarkable ecological and demographic success of humans. Whilst many researchers argue that the roots of human culture lie in social learning, a process widespread in nature, the exact cognitive capacities that set humans apart are not known. To provide a comparative assessment of nine separate hypotheses regarding different social and cognitive factors that may underlie a capacity for cumulative culture, in this thesis a cumulative puzzlebox was presented to three species. Groups of capuchins, chimpanzees and children were provided with the opportunity to solve the puzzlebox to three sequential levels to retrieve rewards of increasing desirability. Higher level solutions spread only in the children. Evidence was found for the occurrence of teaching, imitation, complex communication and prosociality in groups of children, but not in groups of capuchins and chimpanzees. Furthermore, these processes were positively correlated with the performance of individuals within the groups of children which was the only species to show evidence of cumulative cultural learning. Five further hypotheses focussed on alternative social and cognitive factors were not supported by the evidence from this experiment.

Human culture is unique in its scope and complexity and is underpinned by the social transmission of information. Successful individuals will use both social and asocial information effectively. Evolutionary theory suggests that social learning should be guided by evolved learning rules that dictate when individuals rely on social information, a literature which I review across Chapters 1 and 2, with the emphasis of chapter 2 being on conformist transmission. In this thesis I present experimental investigations of the existence and adaptive value of several such strategies in both adults (Chapter 3) and young children (Chapter 4). In all cases I find strong evidence for the existence of such biases and show that they act to increase the accuracy of decisions. In particular I show individuals are highly sensitive to even small majorities within a group of demonstrators. The youngest children (age 3) however, show little sensitivity to social information and do not use it effectively. In Chapter 5 I present an investigation into the role of social learning in the evolution of hominin lithic technology. I conclude that even the earliest hominin flaking technology is poorly transmitted through observation alone and so the widespread and longstanding persistence of such tools implies some form of teaching. Furthermore, I conclude that the stable transmission of more complex technologies would likely require teaching, and potentially symbolic communication. I also postulate a co-evolution of stone tools and complex communication and teaching. In Chapter 6 I conclude that the cultural evolutionary approach, focussing on the evolutionary consequences of social information use and treating culture as a system of inheritance partially independent of genes, seems successful in increasing our understanding of the evolution of social learning.

In this thesis, I explore two subjects of importance to the study of cultural evolution and cumulative culture; behavioural flexibility in chimpanzees, and social transmission in human children. In Chapter 1, I give an overview of current literature on the cognitive requirements of cumulative culture, with a focus on behavioural flexibility as a capacity which facilitates cumulative culture. I also explore a current discussion in the field of cultural evolution; namely the debate between "standard" and cultural attraction-based approaches to the study of cultural evolution. Chapter 2 is an experimental investigation of the capacity of chimpanzees to respond flexibly to a changing foraging task. This study found that chimpanzees did alter their behaviour, but to a limited degree. In Chapter 3 I provide the same artificial foraging task to two further groups of chimpanzees, at a sanctuary in Zambia. This study again found that chimpanzees altered their behaviour in response to task constraints, but also found a significant difference in performance between the two groups tested. Chapter 4 explores one potential factor which may contribute to these group differences; social tolerance. Data on social tolerance from all three groups of chimpanzees is presented. In Chapter 5, I turn to another key factor in the study of culture and also address the cultural attraction approach, by conducting a transmission chain study of four- to eight-year-old human children, comparing the transmission of a symbolic and non-symbolic image. I found that neither image was reliably transmitted along transmission chains. Finally, in Chapter 6, I discuss the findings of the thesis, and suggest that future work considers multiple demographic groups, whether this means the inclusion of multiple groups of apes in studies of non-human primate cognition, or the consideration of how cultural behaviours might be transformed when transmitted by human children rather than adults.

Cette thèse étudie le processus du changement démographique pendant la transition des chasseurs-collecteurs aux agriculteurs sur le plateau de Lœss, qui est la région de l’origine du millet cultivé, et dans la plaine du fleuve Yangszé, qui est la région de l’origine du riz cultivé en Chine. Ce travail de recherche doctoral collecte et analyse les données paléoanthropologiques des nécropoles des deux régions en Chine, et un signal similaire est détecté. Les données archéologiques, comme la densité des sites et la densité des dates au radiocarbone, sont aussi collectées et analysées, pour vérifier ce signal démographique en Chine. Suit à notre étude, nous représentons le contexte environnemental du signal de la TDA, incluant le changement climatique et la variation du paysage. L’amélioration de l’environnement naturel pendant la transition démographique est évidente, mais elle n’est pas une cause décisive de la TDA. Ensuite, nous représentons le changement de la stratégie de subsistance de la population du Paléolithique supérieur au Néolithique dans les deux régions, et son lien de causalité réciproque avec la transition démographique. Les données archéologiques montrent que la transition démographique et le changement de la stratégie de subsistance sont suivis de façon évidente par une modification de l’habitation, et l’arrangement des villages s'est modifié graduellement aussi au fil du temps. Celles-là indiquent probablement que l’augmentation de la taille de population est une cause importante de l’évolution sociale. / In this thesis, we study the process of the demographic change during the transition from the hunters-gatherers to the farmers on the Loess Plateau, which is the region of the origin of the cultivated millet, and in the Yangtze Plain, which is the region of the origin of the cultivated rice, in China. By collecting and analyzing the paleoanthropological data from the cemeteries of prehistorical hunters-gatherers and farmers of these two regions in China, we detect a similar signal of the ADT. This signal is also confirmed by the archaeological data, such as the density of the archaeological sites and the density of the radiocarbon dates. We represent the environmental context of the signal demographic in the following study, including the climatic change and the variation of le landscape. The improvement of the natural environment during the demographic transition is obvious, but it seems that this improvement is not a factor decisive of the ADT. Then we represent the change of subsistence strategy of the population from upper Paleolithic to Neolithic in the two regions, and its relationship of reciprocal causation with the demographic transition. The archaeological data indicate that the demographic transition and the change of the subsistence strategy were evidently followed by the modification of the habitation, and the arrangement of the villages have also varied overtime. These information probably suggest that the augmentation of the size of population is one of the main causes of the social evolution.

Neighbouring plants can interact strongly, competing for resources including light, water, animal mutualists, and local germination sites. From an evolutionary perspective, this implies that a plant’s best resource acquisition strategy will usually depend on the traits of its neighbours, and for plants in particular, neighbours are often genealogical relatives. Here, I use a combination of theory and experiments to expose some important consequences of social interactions among plants. The first model analyzes selection on traits used to attract pollinators, showing that competitive interactions (in the absence of local relatedness) can select for exaggerated secondary sexual characters. To complement this model, I performed experiments that confirm the mechanisms by which adaptive pollinator foraging naturally leads to interactions among plants. The observed foraging behaviour (of bumble bees) also provides unique evidence for ‘Bayesian foraging’, a sophisticated type of resource assessment that depends on prior experience in a particular environment. A second model considers how selection on the sex allocation of cosexual, animal-dispersed plants leads to competition and cooperation over local germination sites, sometimes leading to the origin of gender dimorphism. The model reveals novel ecological contexts in which disruptive selection on sex allocation can arise, and in general, illustrates how selection for cooperation can facilitate or inhibit evolutionary diversification. In the models considered here, cooperation is indiscriminant, but plants might also assess the relatedness of neighbours and cooperate with kin over non-kin. In the final chapter, I present experimental evidence that is consistent with preferential cooperation over soil resources among sibling plants. This study is the first to link a potentially cooperative resource allocation strategy with an increase in the mean fitness of related plants.

Neighbouring plants can interact strongly, competing for resources including light, water, animal mutualists, and local germination sites. From an evolutionary perspective, this implies that a plant’s best resource acquisition strategy will usually depend on the traits of its neighbours, and for plants in particular, neighbours are often genealogical relatives. Here, I use a combination of theory and experiments to expose some important consequences of social interactions among plants. The first model analyzes selection on traits used to attract pollinators, showing that competitive interactions (in the absence of local relatedness) can select for exaggerated secondary sexual characters. To complement this model, I performed experiments that confirm the mechanisms by which adaptive pollinator foraging naturally leads to interactions among plants. The observed foraging behaviour (of bumble bees) also provides unique evidence for ‘Bayesian foraging’, a sophisticated type of resource assessment that depends on prior experience in a particular environment. A second model considers how selection on the sex allocation of cosexual, animal-dispersed plants leads to competition and cooperation over local germination sites, sometimes leading to the origin of gender dimorphism. The model reveals novel ecological contexts in which disruptive selection on sex allocation can arise, and in general, illustrates how selection for cooperation can facilitate or inhibit evolutionary diversification. In the models considered here, cooperation is indiscriminant, but plants might also assess the relatedness of neighbours and cooperate with kin over non-kin. In the final chapter, I present experimental evidence that is consistent with preferential cooperation over soil resources among sibling plants. This study is the first to link a potentially cooperative resource allocation strategy with an increase in the mean fitness of related plants.

The core of sociality and one of the key forces behind the transition to multicellularity is cooperation. The study of social behavior in microorganisms has gained considerable attention in the last decade as researchers have discovered that many of the cooperative social interactions found in higher organisms can also be found in microbes. The dictyostelids are particularly amenable to the study of social evolution because of the potential for conflict and cooperation during multicellular formation. The formation of the multicellular fruiting body may lead to conflict because all nearby cells aggregate together, which may be distinct clones, each trying to increase its own fitness. I first explored how D. discoideum and D. purpureum interact and if either species looks to cheat the other when they interact. I found that both species prefer being clonal but cooperate with each other when it seems the benefits outweigh the costs. Cooperating amoebae are able to make larger fruiting bodies, which are advantageous for migration and dispersal, but both species suffer a cost in producing fewer spores per fruiting body. I next examined short-range social dispersal in the social amoebae, D. discoideum and D. purpureum. It appears that the evolutionary loss of stalked migration gives D. discoideum cells the advantage of delaying specialization and the ability to colonize more distant locations, but has significant costs due to migration distance, such as the fraction of cells that become fertile spores. In my final study, we examine the interaction of different clones of D. discoideum before and after migration. We show that chimerism and migration interact to produce fruiting bodies that have a proportionally higher spore allocation compared to clonal fruiting bodies after migration but were unable to determine whether the results that we see are an indication of clones defecting in a tragedy of the commons or more cooperation. With further study will be able to better explain the affects of cooperation on group dispersal and whether it can be used as a mechanism to reduce local competition.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 294-327).