Abstract The biological approach to culture focuses almost exclusively on processes of social learning, to the neglect of processes of cultural coordination including joint action and shared intentionality. In this paper, we argue that the distinctive features of human culture derive from humans' unique skills and motivations for coordinating with one another around different types of action and information. As different levels of these skills of ‘shared intentionality’ emerged over the last several hundred thousand years, human culture became characterized first by such things as collaborative activities and pedagogy based on cooperative communication, and then by such things as collaborative innovations and normatively structured pedagogy. As a kind of capstone of this trajectory, humans began to coordinate not just on joint actions and shared beliefs, but on the reasons for what we believe or how we act. Coordinating on reasons powered the kinds of extremely rapid innovation and stable cumulative cultural evolution especially characteristic of the human species in the last several tens of thousands of years. This article is part of a discussion meeting issue ‘The emergence of collective knowledge and cumulative culture in animals, humans and machines’.