The Austronesian languages of the Pacific spread across 10,000 kilometers of coastline and sea within 1,500 years, the fastest and widest expansion of prehistoric times. Farmers led the way tng before the major population movements recorded in history, many ancestral forms of the ex isting families of languages had al ready spread across enormous areas of the earth. These families-so called be cause their members show evidence of common descent-bear names that de scribe their ethnic and geographic dis tributions: Indo-European, Afro-Asiat ic, Sino-Tibetan, Austronesian. Why do families of languages sprawl so widely? Why, before the first histori cal empires and colonial frontiers, was the world not covered in a patchwork of unrelated languages? This is the sit uation one would expect if early pop ulations of modern humans and their descendants had always remained in the same regions. Language …