Abstract

For nearly five years, from Dec. 27, 1831, until Oct. 2, 1836, I served as naturalist aboard the H.M.S. Beagle, exploring. During that voyage I was much amazed by how the various types of organisms were distributed around South America, and how the animals and plants presently living on that continent are related to those found only as fossils in the geological record elsewhere. These facts, as will be seen in later chapters, seemed to me to throw some light on the origin of species-that "mystery of mysteries," as it has been called by one of our greatest scientists, John Herschel. After I returned home, it occurred to me in 1837 that I might be able to help address this great question by patiently accumulating and reflecting on all sorts of facts that might have any bearing on it. Finally, after five years of work, I allowed myself to speculate on the subject and wrote up some brief notes. I enlarged these in 1844 into a sketch of the conclusions that seemed to be most probable from the evidence I had collected. Over the subsequent 15 years I have steadily pursued the same object: trying to understand how new species come about. I hope you will excuse me for entering these personal details of my work, as I give them only to show that I have not been hasty in coming to a decision.