This dissertation argues that what drives the emergence of complex communication systems is a process of modular composition, whereby independent communicative dispositions combine to create more complex dispositions. This challenges the dominant view in language-origins research, which attempts to resolve the explanatory gap between (simple) communication and (natural) language by demonstrating how complex syntax evolved. I show that these accounts fail to maintain sensitivity to empirical data: genuinely compositional syntax is extremely rare or non-existent in nature. In contrast, I propose that the reflexive properties of natural language—the ability to use language to talk about language—provide a plausible alternative explanatory target.

Part I provides the philosophical foundation of this novel account using the theoretical framework of Lewis-Skyrms signalling games and drawing upon relevant work in evolutionary biology, linguistics, cognitive systems, and machine learning. Part II provides a concrete set of models, along with analytic and simulation results, that show precisely how (and under what circumstances) this process of modular composition is supposed to work.