Sander E. van der Leeuw is a Foundation Professor at Arizona State University and co-director of the ASU-SFI Center for Biosocial Complex Systems. His research interests include Archaeology of the later Holocene; Ancient and Modern Human-Environment Relationships; Sustainability; Innovation; Complex Systems Approaches; History and Archaeology of Techniques; Urbanization and Urban Dynamics. In 2012 he was awarded the "Champion of the Earth for Science and Innovation" prize by the United Nations Environment Program.Robin Torrence is Senior Fellow, Archaeology and Geosciences at the Australian Museum Research Institute. Dr Torrence's archaeological research focuses on the roles of ancient material culture, especially stone tools, in peoples’ daily lives, social strategies, and exchange systems. Her current research aims to understand social change in western Pacific societies over the past c. 50,000 years, since earliest colonization of the region.