Acknowledgments The Leverhulme Trust is thanked for financial support. Gordon Cook provided radiocarbon dates. Thanks are also due to Andy McMullen for botanical identifications and assistance in the field, and to Sikuu Motzfeld for hospitality during fieldwork. We are also grateful to Emilie Gauthier, Mike Kaplan, Pete Langdon and Alan Gillespie for their comments.Peer reviewedPostprin