The voyage on the Beagle was the defining moment in Charles Darwin's life. He was all set to become a country parson with a hobby in natural history; instead, he turned into the most eminent naturalist of his times, the author of a groundbreaking explanation of biological diversity, and a founding father of a new discipline, evolutionary biology. During his participation in the five-year circumnavigation of the globe on board HMS Beagle (1831–6), Darwin collected an immense amount of material concerning the animal populations, living and extinct, on different continents. In particular the very singular fauna found in South America and the Galapagos Islands would prove illuminating for his theory of the origin of species. Moreover, the publication of his travel report established his reputation as an author, not only in the field of natural history: the popular success of his Voyage of the Beagle was due not least to his skilful mix of serious observations and thrilling adventures, tapping into the Victorian desire for self-improvement as well as the age's machismo.

Darwin's experiences have been transmitted in different textual versions. In his diary, Darwin recorded his daily activities; he did not update the entries day to day, but rather wrote them up during the periods spent on board the Beagle. His prolonged sojourns on the South American mainland were described in retrospect, after his return to the ship. The completed volumes of his diary were sent with his letters to his family – Darwin was writing with a particular audience in mind. Consequently, the diary, although written closer to the events, is not a raw transcription, an ‘authentic’, unmediated record (which remained unpublished until 1933, when it was transcribed and edited by Nora Barlow). It is a self-conscious narrative, aware of its readership, and framed by the cultural preconceptions Darwin carried with him. As will be seen below, the latter inform in particular Darwin's encounters with those population groups he considers uncivilized and, in his own term, savage. The diary constituted the basis for Darwin's published travel report which appeared initially together with Captain FitzRoy's and Captain King's reports on the Beagle’ s two successive voyages.