This contribution, in memory of the Cambridge archaeologist and cultural theorist, David Clarke (1938–76), investigates the possibility of a coherent description of long-term change on an archaeological time scale. It rejects an earlier (‘processualist’) synthesis based on ecology; but, rather than retreat into an introverted and fragmented post-modernism, it asserts the continuing value of a ‘grand narrative’. It identifies the problems of the neo-evolutionary conception prevalent in the 1960s and early 1970s, and in particular a division into stages, and emphasis on autonomous development, and the priority given to production. In contrast, this presentation emphasises the importance of social interaction and cultural encounter. This interactionist approach is exemplified in new descriptions of the ‘Neolithic’, ‘Urban’, and ‘Industrial’ Revolutions, and discussed as a means of conceptualising some general properties of long-term change.