The Evolution and Ecology of Cooperation - History and Concepts -- The Ecology of Altruism in a Clonal Insect -- The Evolutionary Ecology of Eusociality in Australian Gall Thrips: a 'Model Clades' Approach -- The Ecology and Evolution of Helping in Hover Wasps (Hymenoptera: Stenogastrinae) -- Why are so Many Bees but so Few Digger Wasps Social? The Effect of Provisioning Mode and Helper Efficiency on the Distribution of Sociality Among the Apoidea -- Social Plasticity: Ecology, Genetics, and the Structure of Ant Societies -- The Ecology of Social Evolution in Termites -- Kin-Recognition Mechanisms in Cooperative Breeding Systems: Ecological Causes and Behavioral Consequences of Variation -- Social Ecology of Horses -- African Mole-Rats: Eusociality, Relatedness and Ecological Constraints -- Genetic and Ecological Determinants of Primate Social Systems -- The Ecology of Social Life: A Synthesis. Research on the evolution of social behaviour has been dominated by genetic relatedness for a long time; however, both recent empirical studies and theoretical concepts give growing evidence for ecological factors acting as very prominent additional or alternative driving forces in social evolution. Now the time is ripe to investigate similarities and differences in the course of social evolution in different animals. This book brings together renowned researchers working on sociality in different animals. For the first time, they compile the evidence for the importance of ecological factors in the evolution of social life, ranging from invertebrate to vertebrate social systems, and evaluate its importance versus that of relatedness. Answers are given to important questions such as: - Which factors favour group living in social invertebrates and vertebrates? - Are there general differences in the evolutionary forces promoting social life in social insects versus cooperatively breeding vertebrates? - Why are there only so few eusocial vertebrates? - Can relatedness within social groups be a by-product arising from the fact that neighbours are generally kin?