The Cameroonian language Kenyang provides evidence for the view that subjects evolve from topics, and subject agreement morphemes from pronominal subjects. Kenyang has fully grammaticalised clause-internal subjects, and a pre-verbal subject marker that licenses null subjects, as well as marking aspect. Clause-external topics may be involved in subject-like processes such as reflexivisation or control of a null embedded subject, but only through a chain of reference mediated by a co-referential subject. A comparison of topic and clause-initial contrastive focus enables a full characterisation of topic by revealing systematic structural differences. A broadly minimalist analysis provides a straightforward model of the findings.