After briefly laying out a cultural-evolutionary approach to speech acts (Sects. 1–2), I argue that the notion of commitment at play in assertion and related speech acts comprises multiple dimensions (Sect. 3). Distinguishing such dimensions enables us to hypothesize evolutionary precursors to the modern practice of assertion, and facilitates a new way of posing the question whether, and if so to what extent, speech acts are conventional (Sect. 4). Our perspective also equips us to consider how a modern speaker might (...) employ an illocutionary analogue of A.N. Prior’s “runabout-inference ticket”, in which the pragmatic “introduction rules” for utterances correspond to evolutionary precursors of modern speech acts, but in which the “elimination rules” correspond to their modern descendants (Sect. 5). Such behavior would be abusive, though not in a way readily discernible without an evolutionary perspective on speech acts that attends to the dimensions of commitment that they encompass. Such behavior also raises the question how we may safeguard against it in public discourse, and I close (Sect. 6) with some suggestions for doing so. (shrink)