The preface to Darwin's Origin of Species: the curious history of the "historical sketch".

Almost any modern reader's first encounter with Darwin's writing is likely to be the "Historical Sketch," inserted by Darwin as a preface to an early edition of the Origin of Species, and having since then appeared as the preface to every edition after the second English edition. The Sketch was intended by him to serve as a short "history of opinion" on the species question before he presented his own theory in the Origin proper. But the provenance of the "Historical Sketch" is somewhat obscure. Some things are known about its production, such as when it first appeared and what changes were made to it between its first appearance in 1860 and its final form, for the fourth English edition, in 1866. But how it evolved in Darwin's mind, why he wrote it at all, and what he thought he was accomplishing by prefacing it to the Origin remain questions that have not been carefully addressed in the scholarly literature on Darwin.