If history is to be defined in short, it\u2019s a study of change and the causes behind it. The debate or the differences in methodology amongst scholars is over what caused these changes. For instance, for Marxists, all change occurred due to changes in the mode of production, meaning the entire story of human society can be told through changes in the economy and how and why they occurred. There are others who tell the story of change through great men and women through the ages who are seen as being ahead of times. For this school of thought, had there been no such great men and women and their ideas, the world would have been poorer today. Even as these two schools of thought quarrel with each other, demographer Paul Morland, who is an associate research fellow at Birkbeck College, University of London, has attempted to tell the human story through changes in population across the world. The scope of his work, The Human Tide, is ambitious because it is a history of the world since 1800 told through the prism of changes in population. However, unlike Marxists, Morland is not dogmatic and clearly underlines that though population fashioned human history across the globe and is still doing it, it is not the sole agent of change and he doesn\u2019t try to establish the primacy of factors by saying population was the chief agent of change. In his own words: \u201cThe Human Tide is about the role of population in History. It does not argue that the great trends in population\u2014the rise and fall of birth and death rates, the swelling and shrinking of population size, the surges of migration\u2014determine all of history. The case is not made here for a simplistic, monocausal or deterministic view of history. Nor is the claim made that demography is in some sense a primary cause, a first mover, an independent or external phenomenon with ramifications and effects in history but not causes preceding it. Rather, demography is a factor which itself is driven by other factors, numerous and complex, some material, some ideological and some accidental. Its effects are varied, long-lasting and profound, but so are its causes.\u201d Morland has compared population changes in societies with a car, which, in the beginning, moves slowly at more or less the same speed for mile after mile after mile. Then it increases its speed, gradually for the first few miles, then rapidly, until it achieves tremendous, even frightening, velocity. Then after a relatively short distance hurtling along, the brakes are suddenly applied, resulting in rapid deceleration. This is what the world\u2019s population growth pattern has been like since 1800. Within this framework, Morland then puts the growth of countries and continents, their relative decline and the rise of others who were laggards in the beginning. The story began with the British Isles, which saw the beginning of industrial revolution and surge in population. Without going into which of the two came first as it is a useless question, the book says the two were contemporaneous. Birth rates are high in the beginning because death rates are also high when most children don\u2019t even reach their first birthday. If economy and industry develop, as happened in England, birth rates continue to increase, but death rate slowly declines. Gradually, birth rates moderate, but since there are a large number of people in reproductive age, population continues to grow for quite long. It then slows, but by then, better healthcare facilities, which come with economic growth, increase the life span and the population stabilises. With development, women literacy increases and so does their participation in the workforce, which makes women opt for having fewer children. With birth rates continuing to decline and average life span increasing, countries start having an ageing population. Now, Morland brilliantly plots the history of the world, growth and decline of empires across the globe, their phases of crest and trough through this sequence of change in population. France worried and fought Britain because the latter\u2019s population grew faster, its people emigrated to the US, Australia, New Zealand and Canada. When Britain\u2019s population slowed, Germany\u2019s was on ascendant and when it slowed, Russia saw growing numbers. The outbreak of World War I, thus, can also be told through the changing population dynamics of countries. Even during World War II when Britain\u2019s population growth had slowed, it made up by its emigrated population to the US, Australia, New Zealand and Canada. The framework, thus, tells the story of Britain\u2019s rise as a global power, why and when it faced challenges from Germany, Japan and Russia, how the US emerged as a sole superpower, how the long-term decline of economic growth that started with Japan has now spread to Europe, why the Arab Spring came and went, how China rose so meteorically and, finally, why Britain voted for Brexit and the US voted for Donald Trump. Morland is careful to caution in his thesis that population growth can only add to the power of a nation if it is accompanied by economic growth or else the nation will get trapped into the Malthusian trap\u2014there won\u2019t be enough food to feed the rising tide\u2014and there will be disaster. He has interesting nuggets as to how the invention of the pill changed the entire dynamics, not only by checking population growth, but also accelerating pre-marital sex. Before the age of the pill, he says, family planning was done in some societies by delaying marriages, which only deferred population growth, and did not check it. There are stories of how today, in some villages of Russia, there are only eight-10 inhabitants; how Japan has lost steam and several childless, aged people are dying alone in their homes only to be discovered weeks later. Morland also speculates about future changes, which science and technology can bring to population patterns. What would global demography look like if ageing was reversible and people were to live for centuries? What impact would that have on fertility rates? What if birth and sex were entirely divorced and if one\u2019s clone or designer babies could be ordered over the counter? The book is never boring even for a second, and whether world history interests you or not, this book certainly will.