It is not much to look at - a small pitted brass coin with a square hole in the centre-but this relatively innocuous piece of metal is revolutionising our understanding of early East African history, and recasting China's more contemporary role in the region. A joint team of Kenyan and Chinese archaeologists found the 15th Century Chinese coin in Mambrui-a tiny, nondescript village just north of Malindi on Kenya's north coast. In barely distinguishable relief, the team leader Professor Qin Dashu from Peking University's archaeology department, read out the inscription: "Yongle Tongbao" - the name of the reign that minted...