Surveying long stretches of human history, Scheidel concludes that “the big equalizing moments in history may not have always had the same cause, but they shared one common root: massive and violent disruptions of the established order.”
This idea is connected to Thomas Piketty’s Capital in the Twenty-First Century (2013), a New York Times bestseller. Piketty found that “inequality does not go down by itself because we have economic development,” Scheidel said. “His book covers only 200 years and argues that only violent intervention can make that happen.”
Source: https://press.princeton.edu/books/paperback/9780691183251/the-great-leveler (The Great Leveler: Violence and the History of Inequality from the Stone Age to the Twenty-First Century)