From the celebrated neurobiologist and primatologist, a landmark, genre-defining examination of human behavior, both good and bad, and an answer to the question: Why do we do the things we do? Sapolsky's storytelling concept is delightful but it also has a powerful intrinsic logic: He starts by looking at the factors that bear on a person's reaction in the precise moment a behavior occurs, and then hops back in time from there, in stages, ultimately ending up at the deep history of our species and its evolutionary legacy. And so the first category of explanation is the neurobiological one. A behavior occurs - whether an example of humans at our best, worst, or somewhere in between. What went on in a person's brain a second before the behavior happened? Then Sapolsky pulls out to a slightly larger field of vision, a little earlier in time: What sight, sound, or smell caused the nervous system to produce that behavior? And then, what hormones acted hours to days earlier to change how responsive that individua