This report, the first in a two-part study of the Responsible AI landscape by the UKRI’s BRAID programme, provides a chronological and conceptual map of the Responsible AI (R-AI) ecosystem. We chart the role of various actors and communities in this ecosystem’s emergence, especially the vital contributions from the arts and humanities, and the historical development and contestation of different meanings of ‘responsibility’ in the context of AI. In the Preface, we outline the motivation and aims of the study. In Section One, we outline the different meanings and conceptions of ‘Responsible AI’ commonly deployed by different stakeholders. We follow in Section Two with a chronological account of how ‘responsibility’ for the impact of new technologies in computing came to be articulated, culminating in what today we call the Responsible AI ecosystem. We trace this history from the 1950s to the present, concluding in Section Three with a review of seven lessons learned from these ‘first waves’ of Responsible AI research, practice, and advocacy; lessons that can be carried forward in our collective efforts to enable and sustain responsible AI innovation, now and for the future.