The evolution of language and the language faculty
Uniquely among the communication systems of the natural world, human language exhibits combinatorial and compositional structure. Structure in language gives us massive expressive power: at least at a first approximation, anything you can think you can express in language. No other species has a communication system which provides this expressive power. Why do humans? In this talk I'll briefly review some of the evidence (primarily from experimental models of cultural transmission) showing that structure in language can be explained as a consequence of cumulative cultural evolution. I'll then explore what these findings mean for our understanding of the biological basis of human language. Firstly, I'll briefly review some co-evolutionary modelling shows that constraints on language learning are adaptive and can evolve rapidly, but these adaptations only weakly constrain language learning, rather than hard-wiring particular design features into language learners. Secondly, given that this modelling work seems to predict that structure should arise from cultural transmission under fairly general conditions, I'll describe a recent study on cultural evolution of structure in non-human primates. Based on these various sources of evidence, I conclude that language is a product of gene-culture co-evolution, supported by a suite of domain-general capacities, which, if specialised for language at all, are nonetheless highly flexible. We have structured language because we are social, but rather than language being a biological adaptation to this social ecology, it is primarily a cultural adaptation arising from our propensity to learn socially.