In a small dark room at the Wellcome Collection, a stranger told me that the necklace we were both looking at through plastic magnifying glasses was one of the most beautiful things she had ever seen. The necklace was made by Katie Paterson as artist in residence at the Sanger Institute. It is 170 fossils, hand-cut into spheres and arranged in order of age, suspended at eye-height on medical-looking string. The oldest fossil, of archean butterstone stromatolite from present-day South Africa, hangs next to the youngest fossil, from a Cypriot hippo, phanourios minor. The stromatolite is formed of some of the first simple organisms; people were writing in Mesopotamia when the Cyprot hippo was fossilised. Between these points lived woolly rhinos, carcharocles megalodon sharks, dolphins and deer, squid, bison, lobster, mammoths, ink fish, iguanodons, coral, sponge, protozoa, cinnamon trees, winged ants and sea turtle eggs.