Language and social cognition come together in communication, but their relation has been intensely contested. Here, I argue that these two distinctively human abilities are connected in a positive feedback loop, whereby the development of one cognitive skill boosts the development of the other. More specifically, I hypothesize that language and social cognition codevelop in ontogeny and coevolve in diachrony through the acquisition, mature use, and cultural evolution of reference systems (e.g., demonstratives: “this” vs. “that”; articles: “a” vs. “the”; pronouns: “I” vs. “you”). I propose to study the connection between reference systems and communicative social cognition across three parallel timescales—language acquisition, language use, and language change, as a new research program for cultural evolutionary pragmatics. Within that framework, I discuss the coevolution of language and communicative social cognition as cognitive gadgets, and introduce a new methodological approach to study how universals and cross-linguistic differences in reference systems may result in different developmental pathways to human social cognition.