Book excerpt: Why do people raised in the same families often differ more dramatically in personality than those from different families? What made Charles Darwin, Benjamin Franklin and Voltaire uniquely suited to challenge the conventional wisdom of their times? This pioneering inquiry into the significance of birth order answers both these questions with a conceptional boldness that has made critics compare it with the work of Freud and of Darwin himself. During Frank Sulloway's 20-year-research, he combed through thousands of lives in politics, science and religion, demonstrating that first-born children are more likely to identify with authority whereas their younger siblings are predisposed to rise against it. Family dynamics, Sulloway concludes, is a primary engine of historical change. Elegantly written, masterfully researched, BORN TO REBEL is a grand achievement that has galvanised historians and social scientists and will fascinate anyone who has ever pondered the enigma of human character.