This introduction chapter summarizes the other chapters in the two parts of the book. It describes some of the main themes of each chapter and makes comparisons among them. As a sub-discipline of the modern history discipline, world history is surprisingly new. World historians have worked particularly hard to escape the Eurocentrism of so much earlier historical scholarship. The Paleolithic history of the African species is coming into sharper focus, and that makes it more important to integrate Paleolithic history more fully within modern world history scholarship, teaching, and research. The migratory pulses were also shaped by the ancestors' technological creativity and by the slow accumulation of new techniques and new ecological and social understanding, so that, despite the checks and reversals, the ancestors eventually occupied environments ranging from tropical forests to the tundras of Siberia and North America. These Paleolithic movements laid the foundations for everything that would follow in the Holocene history of the species.