to thank the Talensi healers for sharing their information and the Tengzug community and their Chief, the Hon. John Bawa Zuure for hosting this research. The author is also grateful to Dr Ben Kankpeyeng for facilitating the research in many ways, and to Dr Rachel MacLean for reading this paper, although all errors, etc, of course remain the author\'s. The author is grateful to the Wellcome Trust for funding the research. The research was approved by the University of Manchester Ethics Committee, the Ghana Museums and Monuments Board, and the Hon. John Bawa Zuure.

Conflict of interest: none.

Notes on Contributor {#s16}
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Timothy Insoll is professor of archaeology at the University of Manchester. His current fieldwork is in northern Ghana and previously he has worked in Mali, Bahrain, and western India.One day about five years ago, Frank Nolwo, a compact, quietly spoken boat skipper from the upper reaches of the Sepik river, in northern Papua New Guinea, woke up and headed into town. Nolwo, who is 42, has nine children. He was adding an extension to his house, and needed to buy some building materials.

You do not just pop to the shops if you live in the upper Sepik. Nolwo left Kagiru, his village, in the early morning. Like other isolated clutches of palm-roofed houses on the river, Kagiru has no electricity, no mobile phone signal, and no road connecting it to anywhere else. Even by Papua New Guinean standards, the region is regarded as hot, poor and difficult to live in. When it rains, the place floods.