Evolution of combinatorial communication

I will present a work in progress whose aim is to explain why a highly efficient form of communication, in which meaningful units are combined to form new unrelated meanings, is rare in animal signalling systems. I will begin by elaborating on what is meant by combinatorial communication, and present some problematic explanations for its scarcity that have been advanced in the literature. To these explanations I will add our own explanation which is supported by a bunch of evolutionary dynamical equations and some graphs. I will fret about this explanation having its own significant problems, and speculate wildly on how these might be resolved if we pay closer attention to how evolution works at the molecular scale.