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. Part I offers a general consideration of the theme of language distribution and genetic variation in human populations with emphasis on the population-specific polymorphism issue. In parts II and III linguistic variation in Native American populations and their accompanying molecular genetic variability are discussed by leading specialists. In the final part unanswered questions in historical linguistics are debated, including the macrofamily problem with particular reference to the postulated but contoversial Amerind family.