This book examines case studies of North American Quaternary mammalian evolution within the larger domain of modern evolutionary theory. The book presents previously unpublished studies of a variety of taxa (xenarthrans, rodents, carnivores, ungulates) examined over several temporal scales, from a few thousand years during the Holocene to millions of years of late Pliocene and Pleistocene time. Different organisational levels are represented, from mosaic population variation, to a synopsis of Quaternary evolution of an entire order (Rodentia). In addition to specific case histories, the book includes purely theoretical and methodological contributions, for example, on the statistical recognition of stasis in the fossil record, new ways to calculate evolutionary rates, and the use of digital image analysis in the study of dental ontogeny. Perhaps the most important aspect of the studies reported in this book is that they span the time between the 'ecological moment' and 'deep time'. Modern taxa can be traced back into the fossil record, and variation among extant taxa can be used as a control against which variation in the extinct ones can be understood. The book will interest vertebrate palaeontologists, modern ecologists concerned with the origin of biological diversity and also evolutionists interested in the competing evolutionary models of punctuated equilibrium and phyletic gradualism.