1. Department of Microbial Sciences, School of Biosciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
2. Centre of African Studies, School of Oriental and African Studies (SOAS), University of London, Thornhaugh Street, Russell Square, London, WC1H 0XG, UK
3. UCL Institute of Archaeology, 31-34 Gordon Square, London, WC1H 0PY, UK
4. School of History, Archaeology and Philosophy, University of Winchester, Sparkford Road, Winchester, Hampshire, SO22 4NR, UK