ABSTRACT
Hormones play a central role in the lives of many organisms. The coordination of hormonal activities is central for reproductive success, involving life-history trade-offs. A striking phenomenon is hormonal pleiotropy, a term denoting the many-to-many mapping between mediators and the processes they direct. Why could there not be a single dedicated messenger for each target process? One possible answer hinges on the concept of organismal harmony, which requires coordination over time and over all levels of biological organisation. This requires integration of information and an efficient and robust control system. The present chapter explores the idea that a cohesive and comprehensive approach can be derived from the concept of hormones as tokens of evolutionary (selective) pressures.
