Aspects of the prehistory of the Americas currently remain little understood, with suggested dates for the first human colonization varying widely between 40,000 and 14,000 years ago. In this volume molecular geneticists and historical linguists debate the evidence for the first peopling of the Americas, and for the subsequent emergence of the remarkable genetic and linguistic diversity still seen among Native Americans to this day. The arguments against the controversial 'three waves of migration' proposal made by the distinguished linguist Joseph Greenberg are scrutinized. Special attention is given to the theme of 'population-specific polymorphism', that is to say the presence in significant frequencies in individual tribes, language groups or other population units of particular genetic features which serve to distinguish them from other populations. Detailed consideration is given to the case of the Yanomama of the Lowland Amazon. For comparative purposes a case study of long-term continuity among Jewish priests in Israel using Y-chromosome analysis is examined.