While those who study human origins now agree that the evolution of modern human form extends back much further in time than the evolution of modern human behavior, they disagree sharply as to how to interpret the substantive data. Two fundamentally incommensurate interpretations of our origins, the "Replacement" camp and the "Continuity" camp, have now emerged out of pre-existing models and theories that go back to the last quarter of the 19th century. This book contends that these positions are based on radically different biases and assumptions about what the remote human past was like. The purpose of this volume is to examine those conceptual differences, not to arrive at a consensus, but rather to explore the reasons why a consensus might never be possible.