This collection of papers celebrates the career of Ofer Bar-Yosef and his contribution to the study of prehistory. As professor at the Institute of Archaeology at the Hebrew University (1970-1988) and as MacCurdy Professor at Harvard University (1989-present), Ofer has had a huge impact on prehistoric archaeology, fostering multi-national research projects worldwide. With such wide-ranging research interests spanning his career, the editors of this book needed to find a theme which could somehow reflect the entirety of his career so far. The theme they chose was transitions in prehistory, a topic that Ofer has written on from the early phases of his career to the present day. They have called upon students and long-term collaborators to address questions about important transitions in prehistory, dividing the papers into three groups: transitions in the Pleistocene; transitions in the Holocene; and methodological and theoretical transitions, changes in the way archaeologists view the nature of the evidence and our explanations of the archaeological record.