Communication, a process of information transmission between organisms, spans creatures from bacteria to humans. This thesis analyzes communication with an ecological and evolutionary lens. It focuses on how and why information can remain reliable (or ‘honest’) over evolutionary time and across variable ecological settings. To address this question of reliability studies were carried out both in the field and in the laboratory, with a focus on animal communication but with consideration of human language as well. A model invertebrate system (hermit crabs) provides a focal point for experiments. The results highlight the way natural selection can favor reliable information transmission between signalers and recipients. It is shown that reliable information can be guaranteed for cheap-to-produce signals even in circumstances in which signalers and recipients have strongly opposing genetic interests. Ultimately, it is the dynamic coupling of signalers and recipients over evolutionary time that appears to guarantee reliability, even in conflicts. Indeed, in conflicts especially, mechanisms exist that prevent the signaler from changing the informational relationship between its signal and the underlying context that has relevance to the recipient. The thesis concludes by considering how communication and reliability intersect with several adjacent topics, including: social organization, the transition from cues to signals, and cooperation. It is argued that these points of intersection provide fertile territory for building upon the conceptual and empirical results of the thesis to develop a unified, cross-disciplinary model for the study of communication.