1. Department of Geosciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Avenue, Milwaukee, WI 53211, USA
2. Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Brownlow Street, Liverpool L69 3GP, UK
3. The Stone Age Institute, 1392 W Dittemore Road, Gosport, IN 47433, USA
4. Department of Earth and Atmospheric Sciences, Indiana University, 1001 East 10th Street, Bloomington, IN 47405-1405, USA
5. Ngorongoro Conservation Area Authority, PO Box 1, Ngorongoro Crater, Arusha, Tanzania