Darwin had been elaborating his theory of evolution since 1837 and was consciously working on his “Big species book” at least since 1854, when he had to write On the Origin of Species within little more than one year. Consequently, he bluntly presents it as an abstract, with all its contingencies. We usually see “abstract” as a positive quality, for it led Darwin to keep a clear line of argumentation; but he certainly perceived it as a fault. Having amassed hundreds of pages of material, Darwin at first decided to publish his book, only to avoid being forestalled by A. R. Wallace, under the title “the abstract of an essay on the origin of species and varieties through natural selection.” In the first edition of the Origin, Darwin refers constantly to a “longer work” that he was planning to complete. But this was eventually pushed aside by other projects and Darwin’s involvement in the debates launched by the Origin. Instead, Darwin dedicated a lot of time to a careful reworking of his 1859 text, which makes the Origin a book with different versions.

During Darwin’s own life, no less than six successive editions were published by John Murray. In this essay, I follow Morse Peckham’s system of reference: [a] for the first edition (November 1859); [b] for the second (January 1860); [c] for the third (April 1861); [d] for the fourth (December 1866); [e] for the fifth (August 1869); [f] for the sixth (February 1872). This evolution of the Origin was the textual process through which 75 percent of the book underwent modifications, while its global length increased by one-third. All those changes are documented in Peckham’s Variorum text – a book that changed our view of the Origin, although it is an unreadable maze of additions and corrections (Peckham 1959, noted hereafter as Var). Almost everything changed during the long life of the Origin, including its birthdate (from “October 1st, 1859” in [a] to “November 24th” in [d]) and its title (the initial “On” is dropped in [f]).