In this book the author presents an historical examination of sound change and other developments in the very-nearly extinct Gurage language known as Mesmes while also considering the linguistic and social environments in which the language has been lost. The study provides evidence for Mesmes linguistic relatedness with the other Gurage languages and with the Peripheral West Gurage subgroup in particular. The account also considers the impact of phenomena related to language loss and the linguistic effects of contact with Hadiyya, the language to which the Mesmes people have shifted today. The comparative work relies on previously published sources as well as unpublished fieldnotes and also provides the first fully annotated and interlinearized Mesmes text. This examination underscores that historical-comparative work may benefit from serious consideration of external, contact-related phenomena while at the same time not compromising a commitment to shared innovations as determined by the Comparative Method.