The most important aspect of evolution, from a philosophical viewpoint, is the rise of complex, advanced creatures from simple, primitive ones. This "vertical" dimension of evolution has been downplayed, in large part because it was in the past associated with unsavory political views. This avoidance has, however, left evolutionary biology open to the perception that it deals merely with the diversification of similar creatures, all at the same level of "advancedness," from a common ancestor--for example, the classic case studies of finches with different beaks. The latest incarnation of creationism, dubbed Intelligent Design (or ID), has taken advantage of this. It portrays an evolutionary process that is guided--especially in its upward direction--by the hand of an unseen Creator, to ensure that it ends up producing humans. This book builds a persuasive picture of how "unaided" evolution produces advanced creatures from simple ones by an essentially accidental process.--From publisher description.