Compositionality, Metaphor, and the Evolution of Language

Abstract

One of the great unknowns in language evolution is the transition from unstructured sign combination to grammatical structure. This paper investigates the central — while hitherto overlooked — role of functor–argument metaphor. This type of metaphor pervades modern language, but is absent in animal communication. It arises from the semantic clash between the default meanings of terms. Functor–argument metaphor became logically possible in protolanguage once sufficient vocabulary and basic compositionality arose, allowing for novel combinations of terms. For example, the verb to hide, a functor, could be combined not only with a concrete, spatial entity like food as its argument, but also with an abstract, non-spatial one like anger. Through this clash, to hide is reinterpreted as a metaphorical action. Functor–argument metaphor requires the possibility of term combinability and the existence of compositionality. At the same time, it transcends compositionality, forcing a non-literal interpretation. We argue that functor–argument metaphor led the development of protolanguage into fully-fledged language in multiple ways. Not only did it expand expressiveness, but it drove the development of syntax including the conventionalization and fixation of word order, and the development of demonstratives. Thus, functor–argument metaphor fills in multiple gaps in the trajectory from a protolanguage, with only some terms and simple term combinations, to the elaborate grammatical structures of fully-fledged human languages.