For a long time the most isolated tree on Earth was an acacia in the Ténéré desert in Niger, with no other tree for something like 400 kilometres in any direction. It was a landmark on the caravan routes and was marked on maps. When a well was dug beside it in 1938 and 1939, the diggers found its roots going down to water about 35 metres below the sand, which explained how it had managed to stay. In 1973 a truck driver ran into it and broke the trunk. What was left was taken to the national museum in Niamey, and a metal sculpture now marks the spot. It’s easy to tell this as a story about carelessness, and it probably was one. But there’s something else in it. Across hundreds of kilometres of open sand, that tree was the one thing anybody was driving towards, and whatever everyone aims for has to put up with being aimed at.