In the desert of the United Arab Emirates, there is an unusual series of flat discs imprinted in the sand.  Each one is about 40 centimetres wide, and they snake off into the distance in several parallel lines, for hundreds of metres.

They are tracks. They were made by a herd of at least 14 early elephants, marching across the land between 6 and 8 million years ago. The track-makers are long dead, but in the intervening time, nothing has buried their tracks or eroded them away. Today, their social lives are still recorded in their fossilised footsteps.

The site, known as Mleisa 1, provides the oldest evidence for proboscideans – elephants and their close relatives – living in a herd. Covering