Charles Darwin's On the Origin of Species has been one of the most influential and provocative books of modern civilization. While Darwin's theory of evolution has come to be regarded as part of scientific orthodoxy, it has also remained the object of continual debate and controversy throughout the 130 years that have elapsed since he first put forward his ideas, facing repeated attack from religious fundamentalists and creationists, and continuing to be a subject of contention among scientists themselves. In this book, Ernst Mayr, who has himself made contributions to modern evolutionary thinking, traces the history of Darwin's theories, showing the complexity of Darwin's thought and the varying interpretations, understandings and misunderstandings of those theories from Darwin's own time to the present day. Darwin did not put forward a single theory of evolution and his supporters and intellectual heirs have interpreted his theories in widely different ways, accepting some parts of his thought and misunderstanding or rejecting others.