25.10.2022 - Uta Reinöhl, T. Mark Ellison

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 in this transition. 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 to allow 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. 

The central requirement for functor–argument metaphor is compositional meaning construction in the language. At the same time, such metaphor transcends compositionality, forcing nonliteral interpretations. 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, the development of demonstratives, and grammaticalization. Thus, functor–argument metaphor bridges multiple gaps in the trajectory from protolanguage to the elaborate grammatical structures of fully-fledged modern human languages.