In 1866 French engineer Peccadeau de l’Isle discovered the sculptures of two swimming reindeer on the banks of the River Aveyron. Each had been carved from a mammoth tusk about 13,000 years ago. The carvings had historic as well as artistic value: They showed that humans, mammoths, and reindeer had coexisted in France during the ice age, when the climate of France resembled that of modern Siberia.

Amazingly, it wasn’t until 1904 that anyone thought to try fitting the two pieces together — it was discovered that they were two parts of a single sculpture. Today they form the oldest piece of art in the British Museum.