The ‘Introduction’ identifies the purpose of this book—to introduce the general reader to some of the most important basic findings, concepts, and procedures of evolutionary biology. Evolution provides a set of unifying principles for the whole of biology; it also illuminates the relation of human beings to the universe and to each other. In addition, many aspects of evolution have practical importance. The study of evolution has revealed our intimate connections with the other species that inhabit the Earth; if global catastrophe is to be avoided, these connections must be respected. An overview of the following chapters is also provided.