Among Darwin’s brilliant ideas was his (1871) conception of animal communication signals as adaptive characteristics of a species. The idea was subsequently taken up by the ethologists of Europe in the 1930s (Lorenz, Tinbergen, and von Frisch in particular) in their studies of animal signaling systems in nature. For many subsequent researchers, human language was the implicit model for an animal communication system. Although not expecting the same level of complexity, these researchers assumed that animal signals transmitted information from sender to receiver that was honest, and that benefitted them both. However, the honest signaling/mutual benefit view was challenged by new researchers steeped in the sociobiology and behavioral ecology movement of the 1960s. The emphasis on competition in this new field inspired these researchers to reconceive the animal signaling process as one in which the sender manipulates the receiver to the sender’s advantage. This view was challenged in turn when researchers recognized that the receiver was not a passive party in the interaction, but fully capable of manipulating the sender to its advantage. The communication interaction can be viewed as an arm’s race. The handicap principle—the idea that honesty in signaling can be maintained if signals are costly—is one way the receiver may gain an edge in this competition. Eventually, game theory considerations led to the development of a revised perspective in which signals evolve only when both the sender and the receiver benefit on average, and where signals are honest on average. Researchers examining a particular signaling system’s signals these days ask not are the signals honest, but how reliable are the signals.