This book provides a behind-the-scenes look at one of the most powerful and revolutionary ideas in world history — the theory of evolution. It traces the development of this momentous concept through the autobiography, letters, and notebook excerpts of the man who conceived the theory and introduced it to the world. Darwin's revealing autobiography is accompanied by the illuminating commentary of his son Francis as well as hundreds of letters to and from such luminaries as Henslow, Lyell, Hooker, Huxley, Wallace, and Kingsley. The book covers Darwin's schooling, his five-year stint as the Beagle's onboard naturalist, and his early insights into the mechanism of evolution in addition to his later observations. Subsequent chapters trace the scientist's steady accumulation of facts; the writing, publication, and defense of his landmark publication, On the Origin of Species; the spread of the doctrine of evolution; and the writing and publication of other works, including The Descent of Man. Few books hold such inherent interest, not only for biologists, historians, and psychologists but also for everyone wishing to understand the development of one of the major milestones in the history of science.