Evolution of Communication - Volume 3, Issue 2, 1999

We extend previous work by modeling evolution of communication using a spatialized genetic algorithm which recombines strategies purely locally. Here cellular automata are used as a spatialized environment in which individuals gain points by feeding from drifting food sources and are 'harmed' if they fail to hide from migrating predators. Our individuals are capable of making one of two arbitrary sounds, heard only locally by their immediate neighbors. They can respond to sounds from their neighbors by opening their mouths or by hiding. By opening their mouths in the presence of food they maximize gains; by hiding when a predator is present they minimize losses. We consider the result a 'natural' template for benefits from communication; unlike a range of other studies, it is here only the recipient of communicated information that immediately benefits.A community of'perfect communicators' could be expected to make a particular sound when successfully feeding, responding to that same sound from their neighbors by opening their mouths. They could be expected to make a different sound when 'hurt' and respond to that second sound from their neighbors by hiding.Suppose one starts from a small set of 'Adam and Eve' strategies randomized across a cellular automata array, and uses a genetic algorithm which operates purely locally by cross-breeding strategies with their most successful neighbors. Can one, in such an environment, expect evolution of local communities of 'perfect communicators'? With some important qualifications, the answer is 'yes'.

Many species produce specific alarm vocalizations when they encounter predators. There is considerable interest in the degree to which bird, ground-dwelling sciurid rodent, and primate alarm calls denote the species or type of predator that elicited the vocalization. When there is a tight association between the type or species of predator eliciting an alarm call, and when a played-back alarm call elicits antipredator responses qualitatively similar to those seen when individuals personally encounter a predator, the alarm calls are said to be functionally referential. In this essay I aim to make two simple points about the evolution of functionally referential alarm communication. Firstly, functionally referential communication is likely to be present only when a species produces acoustically distinct alarm vocalizations. Thus, to understand its evolution we must study factors that influence the evolution of alarm call repertoire size. Secondly, and potentially decoupled from the ability to produce acoustically distinctive alarm vocalizations, species must have the perceptual and motor abilities to respond differently to acoustically-distinct alarm vocalizations. Thus, to understand the evolution of functionally referential communication we also must study factors that influence the evolution of context-independent perception. While some factors may select for functionally referential alarm communication, constraints on production or perception may prevent its evolution.

Exclamations, manners of speaking, performative verbs, and vocal gestures such as laughter frequently cannot be "translated" into propositional language without losing their identity as actions in some way. But not all exclamations, performatives, and vocal gestures are alike in this respect. Some can be translated, and some lie somewhere in between on a "sublimation trajectory" from doing to saying. Intermediate points on this trajectory correspond to attested stages of child language acquisition, and may also correspond to stages in the phylogenetic evolution of language.

One of the most prominent questions in connection with language evolution is whether the human capacity for language can be related to any capacities found in animals. Evolutionary continuity in anatomical structures involved in language is obvious, but in the case of cognitive capacities and behavior it is rather controversial. A correlation has often been implied between quantitative difference and evolutionary continuity on the one hand and qualitative difference and evolutionary discontinuity on the other. Recently these two positions have even incorporated claims of gradualistic and punctuated evolution of language respectively. These suggested correlations can hardly be true because the question of the rate and curve of language evolution is only indirectly connected to the continuity-discontinuity debate. It is highly unlikely that there could be true discontinuity in language evolution due to the lack of any antecedent trait. Rather, seeming missing links can also occur in the case of continuous traits when there is enhanced selection pressure due to rapid or even sudden environmental changes and hence rapid evolutionary change takes place. This is more logical even from an adaptationist point of view than a constant rate evolution. Thus, while elements of the primate communication system, cognitive capacity and social behavior must have served as evolutionary forerunners of language in the form of preadaptations, the rate and curve of language evolution must have depended on the selection pressures driving it.