Evolution

Evolution is a series of changes in which the nature of each step depends on what has gone before. Such related changes, produced by man or by natural forces, have occurred in many connections; accordingly, there have been many evolutions. Men's thought have never changed radically in a single step; they have always retained much of the flavor of their immediate antecedents. The sciences have changed, but new discoveries are never seen without relation to what was believed to be true just before they were made. The connected, interdependent series of changes that have occurred or are occurring in living beings is called organic evolution. Every step of that evolution has depended on preceding steps. How the new has arisen out of the old is the subject matter and greater part of this book.