We are a weird species. Like other species, we have a culture. But by comparison with other species, we are strangely unstable: human cultures self-transform, diverge, and multiply with bewildering speed. They vary, radically and rapidly, from time to time and place to place. And the way we live--our manners, morals, habits, experiences, relationships, technology, values--seems to be changing at an ever accelerating pace. The effects can be dislocating,...