The Acheulean is the longest archaeological period in history, and was produced by different hominin species such as Homo erectus and Homo heidelbergensis. In this book the author examines the diagnostic stone tools of the Acheulean period, handaxes and cleavers, from the Hunsgi-Baichbal Valley in India. At the 1.2-million-year-old site of Isampur Quarry, the author reconstructs the manufacturing process for these tools and uses it to infer some of the social and cognitive faculties of their makers. The Isampur Quarry tools are then compared with those from other sites in the Valley, including one around a million years younger, and the author deduces some of the changes in social interaction and cognition that occurred over the vast timespan of the Acheulean.