A dazzling new history of the irrepressible demographic changes and mass migrations that have made and unmade nations, continents, and empires The rise and fall of the British Empire; the emergence of America as a superpower; the ebb and flow of global challenges from Nazi Germany, Imperial Japan, and Soviet Russia. These are the headlines of history, but they cannot be properly grasped without understanding the role that population has played.The Human Tide shows how periods of rapid population transition -- a phenomenon that first emerged in the British Isles but gradually spread across the globe--shaped the course of world history. Demography -- the study of population -- is the key to unlocking an understanding of the world we live in and how we got here. Demographic changes explain why the Arab Spring came and went, how China rose so meteorically, and why Britain voted for Brexit and America for Donald Trump. Sweeping from Europe to the Americas, China, East Asia, the Middle East, and North Africa, The Human Tide is a panoramic view of the sheer power of numbers.