VIETNAM: A grinding stone used to shape, repair, and maintain stone axes attests to the unexpected presence, some 3,500 years ago, of specialized toolmakers at the southern Vietnamese site of Rach Nui. Previously it was thought that the manufacture of stone tools only occurred near the sources of material, but the closest quarry to Rach Nui is 50 miles away. Researchers now believe a sophisticated Neolithic trade network enabled raw materials to be imported into Rach Nui, where they were crafted into finished products. —Jason Urbanus