Book excerpt: New perspectives on transitions in human history This book is about transitional periods of cultural and environmental change as seen through the lenses of archaeology and ethnography. Incorporating data from across six continents and tracing the human experience from the Late Pleistocene to the present, these chapters offer a global comparative perspective on transitional states. Questions of causality are considered, as are hypotheses about the processes of cultural change. Archaeology on the Threshold focuses on major transitions such as the shift from foraging to agriculture, the adoption of new technologies, the emergence of large-scale societies, the transition from egalitarian to inegalitarian leadership, and changes that occur in socioeconomic and ideological systems as a result of climate change and disease. Theoretical approaches range from processual to postprocessual, humanistic, and interpretive. Methodologies include ethnoarchaeology, the use of ethnographic analogy, cross-cultural comparisons and large-scale data approaches, oral history, the historical record, participant observation, and focus group discussions. Challenging archaeologists to query long-held assumptions and theoretical positions, this volume aims to refocus inquiry into change-causing and larger evolutionary processes to problematize notions of revolutionary, irrevocable change. These case studies examine and shed light on assumptions regarding the linearity and oscillations of adaptations, with intriguing implications for archaeological inferences.