This book grew from small beginnings as I began to find unexpected patterns emerging from the data in the literature. The more I thought about the way in which primate social systems worked, the more interesting things turned out to be. I am conscious that, at times, this has introduced a certain amount of complexity into the text. I make no apologies for that: what we are dealing with is a complex subject, the product of evolutionary forces interacting with very sophisticated minds. None the less, I have done my best to explain every­ thing as clearly as I can in order to make the book accessible to as wide an audience as possible. I have laid a heavy emphasis in this book on the use of simple graphical and mathematical models. Their sophistication, however, is not great and does not assume more than a knowledge of elementary probability theory. Since their role will inevitably be misunderstood, I take this opportunity to stress that their function is essentially heuristic rather than explanatory: they are designed to focus our attention on the key issues so as to point out the directions for further research. A model is only as good as the questions it prompts us to ask. For those whose natural inclination is to dismiss modelling out of hand, I can only point to the precision that their use can offer us in terms of hypothesis-testing.

1. Primates and their Societies.- Asking the Right Questions.- The Primate Heritage.- Primate Social Systems.- 2. Theory of Reproductive Strategies.- An Evolutionary Perspective.- Optimal Strategy Sets.- A Question of Ontogeny.- Structure and Function in Primate Society.- 3. Survival Strategies.- Nutritional Requirements.- Dietary Strategies.- Optimal Foraging.- Exploiting the Habitat.- Economics of Territoriality.- The Problem of Predation.- 4. Demographic Processes: (1) Lifehistory Variables.- Lifehistory Variables.- Variance in Birth Rates.- Mortality Rates.- 5. Demographic Processes: (2) Population Parameters.- Population Dynamics.- Migration and Fission.- Sex Ratio.- 6. Time Budgets and Other Constraints.- Time Budgets.- Demographic Constraints on Behaviour.- 7. Evolution of Grouping Patterns.- Why Form Groups?.- Costs of Group-living.- Evolution of Groups.- Evolution of Social Structure.- 8. Mating Strategies.- Reproductive Behaviour in Primates.- Gaining Access to Mates.- Male Lifetime Reproductive Success.- Alternative Strategies of Mate Acquisition.- 9. Rearing Strategies.- Primate Rearing Patterns.- Ecology of Motherhood.- Social Aspects of Rearing.- Male Parental Investment.- 10. Conflicts and Coalitions.- The Constraint-free Strategy.- Economics of Coalition Formation.- Demographic Considerations.- Acquisition of Rank.- 11. Mechanics of Exploitation.- Processes of Negotiation.- Dynamics of Social Relationships.- Role of Communication.- Exploiting Others.- Infanticide as a Reproductive Strategy.- 12. Socio-ecological Systems.- Models as Descriptive Tools.- Models as Analytical Tools.- The Problem of Monogamy.- Comment:The Function of Territoriality.- A Note on the Use of Modelling.- 13. Evolution of Social Systems.- Social Evolution in Baboons.- Social Evolution in the Great Apes.- Conclusion.- Scientific and Common Names.- References.