It is essential in language evolution research to use a clear definition of what language is, i.e. the set of abilities that make up the human language capacity. Recently, a growing list of behaviours has been recognised to be of importance to language: not only speech and manual signs, but gesture, facial expression and prosody, among others. The integration of these behaviours into linguistic theory and experimentation might suggest that we need to reassess the dividing line between linguistic and non-linguistic behaviours, which in turn may have consequences for how we characterise the evolutionary history of the human language capacity, and what we think is the crucial difference between human language and communication in other species. In this workshop, we invite participants to consider which communicative behaviours might be considered linguistic, how behaviours traditionally thought to be non-linguistic become integrated into a linguistic system, and to what extent the divide between linguistic and non-linguistic behaviours is useful to our understanding of human language.