Drawing on data from archaeology, anthropology, biology and history, Iain Morris, author of the bestselling book Why the West Still Rules, offers a compelling explanation for the evolution of human values, arguing that the most fundamental of all forces is behind principled long-term value changes - energy. People have come up with three main ways to get the energy they need: gathering, farming and using fossil fuels. In tiny squads of gatherers, those who value equality but are willing to solve conflicts through violence live best; in large agricultural societies, those who value hierarchy and are less likely to resort to violence are most advantaged; finally, in giant societies of fossil-fuel consumers, the pendulum swung again toward equality, but further removed itself from violence.