Increased population density is among the proposed drivers of the behavioural changes culminating in the Middle to Later Stone Age (MSA–LSA) transition and human dispersals from East Africa, but reliable archaeological measures of demographic change are lacking. We use Late Pleistocene–Holocene lithic and faunal data from Nasera rockshelter (Tanzania) to show progressive declines in residential mobility—a variable linked to population density—and technological shifts, the latter associated with environmental changes. These data suggest that the MSA–LSA transition is part of a long-term pattern of changes in residential mobility and technology that reflect human responses to increased population density, with dispersals potentially marking a complementary response to larger populations. This article is part of the themed issue ‘Major transitions in human evolution’.