Gender flip and person marking in Benchnon (North Omotic)

Subject agreement in the North Omotic language Benchnon (Rapold 2006) lacks dedicated person marking, but indirectly indicates person distinctions through asymmetries in the distribution of gender markers. In one verbal paradigm, first and second person subjects are expressed by feminine morphology, and in the other paradigm they are expressed by masculine morphology. This is hard to reconcile with any known notion of how gender assignment works. I show that it can be explained as the particular instantiation of a rare but cross-linguistically recurrent pattern in which a (reduced) person marking system is generated by restrictions on gender agreement: only third person subjects control semantic gender agreement, while first and second person are assigned default gender. In Benchnon the default gender switched from feminine to masculine over the course of its history, yielding two contrasting verbal paradigms. The older one is morphologically frozen, the newer one is a reflection of still-active agreement conditions. Further developments show that the older paradigm can be adapted to conform to the newer conditions, showing that the division between morphosyntactically motivated and arbitrarily stipulated morphology is a fluid one.