1. GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia.
2. Department of Statistical Science, University College London, London WC1E 6BT, UK.
3. Iziko Museums of Cape Town, Cape Town 8000, South Africa.
4. Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory (ACT) 0200, Australia.
5. School of Archaeology and Anthropology, Australian National University, Canberra, ACT 0200, Australia.