Open Access via the Springer Compact Agreement. This research was supported by an Australian Government Research Training Program (RTP) Scholarship, Australian Research Council; Grant number: FT 120100299; and Institute of Advanced Study (IAS), Durham University and The COFUND ‘Durham International Fellowships for Research and Enterprise’ scheme. We also thank Les O’Neill, Archaeology Programme, University of Otago, for creating Figure 1.Peer reviewedPublisher PD