As the sequel to Groups: The Evolution of Human Sociality (Trans Pacific Press, 2013), this book continues to present the cutting-edge studies conducted jointly by sociological primatologists and ecological anthropologists in Japan. They seek to discover the essential qualities of ‘institutions’ by tracing back to the world of apes and monkeys, where ‘natural institutions’ are formed without the medium of language. To comprehend the characteristics of contemporary institutions, the authors find it necessary to go back to the origin of the evolutionary process and then uncover the gradual development through the hunter-gathering phase to the modern era. The chapters examine institutions from a diverse range of evolutionary angles, including such topics as encounters with death, children’s games, cattle rustling and mathematical proofs, and attempt to show how the concept of institutions can be applied to these settings. This collaborative work between primatologists and anthropologists shows that the understanding of ‘pre-institutional phenomena’ in the world of non-human primates is essential to modern human institutions.