The earliest known stone tools are simple flakes chipped roughly from a core, called the Oldowan tradition. The more advanced Acheulian culture followed, characterized by leaf-shaped bifaces or hand axes. The Acheulian is thought of as the signature technology of Homo erectus. The timing of the emergence of the Acheulian remains unclear because well-dated sites older than 1.4 million years are scarce. A new stratigraphic study at the Kokiselei archaeological site in West Turkana in Kenya, where both Oldowan and Acheulian tools are found, has yielded the worlds oldest Acheulian stone tools, dating to 1.76 million years old 350,000 years older than the previous earliest-known record of Acheulian artefacts. As the first records of hominins outside Africa include either no tools or only Oldowan-type tools, the research also suggests that the first Eurasian hominins to have left Africa might not have taken Acheulian culture with them. On the cover, a large crude handaxe (KS4-203) shaped by hard hammer percussion from a flat phonolite pebble (P.-J. Texier/MPK/WTAP).