"Darwin gave us a theory of why living things have the traits they have, not just their bodily traits but the basic mindsets and motives that drive their behavior. A hundred and fifty years after the Origin of Species was published, the theory of natural selection has been amply verified in the lab and field, and has been augmented with ideas from new fields of science and mathematics to yield a coherent understanding of the living world. These fields include genetics, which explains the replicators that make natural selection possible, and game theory, which illuminates the fates of goal-seeking agents in a world that contains other goal-seeking agents."