Book excerpt: Have you ever wandered why men don't ask for directions? Why we react with anger to infidelity? Why we love music and art? Why war and racism still thrive in our most sophisticated cultures? In this fascinating synthesis of the disciplines of anthropology, psychology, linguistics, philosophy, and biology, William Allman shows us how our minds have evolved in response to challenges faced by our prehistoric ancestors, and reveals how our brains continue to harbor that legacy in the present day. Scientists speculate that many of the problems of modern life -- from obesity to war -- arise because our "Stone Age mind" hasn't caught up with our technologically sophisticated world. But Allman also reveals how morality, rather than being the result of arbitrary convention, is deeply rooted in our need to cooperate, which has been essential to the survival of our species through its evolution.