The historiographical vision of social mobility in the Roman Empire changed from that of a "caste society" in the late nineteenth and early twentieth centuries, to its antithesis in the 60s. The fourth century AD came then to be seen as a period marked by an unusual frequency of ascending careers of new men that gained entrance to the imperial elite. Recently, however, some authors have proposed a frontal attack on this thesis, rejecting the reality of the alleged social mobility in this period. My goals in this paper are, first, to provide a brief overview of the historiographical debate on this subject and, second, to present the analysis of a very special case of mobility, the career of a humble late Roman African farmer, whose economic success allowed him to join the curial order of his city, Mactar. We know history through the extensive verse epitaph on his tombstone. The name of this farmer is lost, so he is usually designated as the "Mactar Reaper". His case is particularly interesting because it presents an example of mobility linked to an economic accumulation through a successful activity in the market, a pattern of upward mobility that has been virtually ignored in the historiography on the sub [ABSTRACT FROM AUTHOR]