This book investigates the evolutionary and social mechanisms that drive the formation of coalitions and alliances among humans and non-human animals. Alexander H. Harcourt and Frans B. M. de Waal, both distinguished researchers in primatology and behavioral ecology, synthesize extensive field observations and comparative data to explain why individuals cooperate during intra-species conflicts. The authors argue that these strategic partnerships are fundamental to understanding social hierarchy, reproductive success, and the structural complexity of animal societies.

Experts recognize this work as a foundational text for understanding the biological underpinnings of social cooperation. Readers frequently note the academic density of the prose, which provides a rigorous examination of behavioral ecology for students and researchers alike.