In 1988, he moved to the United States of America where he became Professor of Prehistoric Archaeology at Harvard University as well as Curator of Palaeolithic Archaeology at the Peabody Museum of Archaeology and Ethnology.
I 1988 flyttede han til USA, hvor han blev professor i forhistorisk arkæologi ved Harvard University samt kurator af palæolitiske arkæologi ved Peabody Museum of Archaeology and Ethnology.