Animal communication can be defined as the provision of information that benefits the sender that is ensured by influencing the receiver into a response; this is known as a signal. Signals can be behavioural, physiological or morphological characteristics formed or preserved by natural selection because they allow communication between animals (Otte 1974). However animals also posses the ability to inadvertently produce stimuli, that can be exploited by other animals in a process known as eavesdropping. When an animal provides information in this manner it is known as a cue (Bradbury and Vehrencamp 1998).
Communication when regarded from a functional and evolutionary point of view is a social adaptation. The activity and presence of living organisms in a given environment will directly affect the continued survival and reproductive success of an animal either of the same species or different. Thus sexual and natural selection has and will continue to determine the ability animals have in exchanging information. Communication is a complex process that uses different sensory channels to send and receive information. The use of visual, tactile, chemical, auditory and electrical signals by different living organisms allows them to exchange information however complex, over varying distances at different rates. Communication as a social adaptation has many purposes ranging from use in agonistic interactions, mating rituals to food related signals. This includes the large multi-coloured feathered tail of the peafowl that is used to charm and excite members of the opposite sex when selecting sexual partners (Ruse 2008). Through evolutionary development whole brain structures have arisen, solely devoted to controlling the Syrinx, the vocal organ some birds use to convey fitness in sexual selection rituals (Read and Weary 1990). Even the small red spot on a herring’s bill that may seem insignificant has a complex evolutionary explanation (Drury and Smith 1968). Understanding communication from an evolutionary perspective means pin pointing various selective pressures that are responsible for the differences in how animals communicate and what information they exchange.
The first step to understanding the evolution of communication, is understanding the processes by which an animal that was previously lacking in a vital feature and behaviour acquired it. For example Julian Huxley and Edmund Selous were the first to describe the means by which evolution worked in the production animal displays such as that of threat and courtship (Lorenz 1966). They noticed that a large amount of the movements that governed communication were similar, if slightly different to the movements that were used in completely different functions in the normal everyday activity of an animal (Lorenz 1966). Julian Huxley and Edmund Selous made evident that communication movements had evolved from everyday activity of an animal, and named this process reutilization (Lorenz 1966). Ritualized movements are easily recognizable and are one of the fastest evolutionary processes that affect undomesticated animals. This can be seen by the comparative studies that show the dissimilarities of species that are closely related. The comparative study of closely related species can show that certain movements can be interoperated to depict communication between a signal sender and receiver. These movements would otherwise show no communicative function in their most primitive forms. The ability for these ritualised movements to grow in to more specialised and complicated signals can be depicted by the study of grass finches done by Desmond Morris (Morris 1958). The primitive beak wiping movement used for a preening function was observed in many of the species, however in some of the species this movement has been developed to be used as a signal during courtship (Morris 1958).
The next step is...