Cumulative cultural evolution, population structure and the origin of combinatoriality in human language

Abstract

Language is the primary repository and mediator of human collective knowledge. A central question for evolutionary linguistics is the origin of the combinatorial structure of language (sometimes referred to as duality of patterning), one of language’s basic design features. Emerging sign languages provide a promising arena to study the emergence of language properties. Many, but not all such sign languages exhibit combinatoriality, which generates testable hypotheses about its source. We hypothesize that combinatoriality is the inevitable result of learning biases in cultural transmission, and that population structure explains differences across languages. We construct an agent-based model with population turnover. Bayesian learning agents with a prior preference for compressible languages (modelling a pressure for language learnability) communicate in pairs under pressure to reduce ambiguity. We include two transmission conditions: agents learn the language either from the oldest agent or from an agent in the middle of their lifespan. Results suggest that (1) combinatoriality emerges during iterated cultural transmission under concurrent pressures for simplicity and expressivity and (2) population dynamics affect the rate of evolution, which is faster when agents learn from other learners than when they learn from old individuals. This may explain its absence in some emerging sign languages. We discuss the consequences of this finding for cultural evolution, highlighting the interplay of population-level, functional and cognitive factors. This article is part of a discussion meeting issue ‘The emergence of collective knowledge and cumulative culture in animals, humans and machines’.

The emergence of collective knowledge and cumulative culture in animals, humans and machines

“…Beyond these case studies in animal communication, Kirby & Tamariz [ 156 ] demonstrate that cultural evolution can also explain the origins of one of the fundamental design features of human language, duality of patterning. Using simulations they show why some young emerging sign languages exhibit this feature to a greater or lesser extent, arguing that learning from other learners as opposed to adults radically increases the rate of evolution.…”

The origins of human cumulative culture: from the foraging niche to collective intelligence

“…In later hominins with larger and more interconnected social networks, language might have evolved into speech as a more complex communication technology [ 143 , 144 ]. Similarly to stone tool technology, speech-based language is a system of multipart tools (or sentences) built from vocalization units and could therefore have evolved through cultural recombination [ 145 ]. In summary, the foraging niche may have provided the selective context for the evolution of cognitive and cultural abilities underlying human cumulative culture.…”

Collective minds: social network topology shapes collective cognition

“…Unlike herds and swarms, human communities comprise social networks with diverse structures. A number of papers in the present special issue focus on cumulative cultural evolution and the structure of populations as the origins of moving from foraging to collective intelligence, while others shed light on the social networks of hunter–gatherers to understand cultural evolution (see [ 59 , 60 ]; as well as [ 61 ]). While the burgeoning research on social learning across the species points at cultural evolution and collective knowledge (see Garland et al .…”