Discovered on the southern flank of the ancient volcano called La Denise located near the town of Le Puy-en-Velay in the southeastern French Massif Central (Aymard, 1844), "La Denise fossil man" is a little-known object today but was of a major interest at the time of the emergence of the prehistoric discipline. As soon as these human remains came to the light, they triggered a controversy over their authenticity and their age. This controversy has continued for over a century, until the recent age of these bones was established in 1969 (Heintz & Oakley, 1969), reinforcing doubts on a fake. In terms of current thinking on scientific knowledge, this case study is interesting to examine the persistency of an archaeological forgery (Kaeser, 2001). More specifically, it raises the question of how and why the authenticity and the age of this discovery are justified over time. An analysis of scientific publications and archives related to these human remains will provide a clearer picture of how this controversy unfolded and worked. Our development will be chronological, outlining the basis of a biography of this object (Bonnot et al., 2018). The other goal of this paper is to show how the tension between residential knowledge and cosmopolitan knowledge (Kohler, 2006) can explain the persistency of this forgery. First, we will focus on the way in which "La Denise fossil man" was defended when the high antiquity of man was not yet recognised by the scientific community. We will then take a closer look at the uncertainties surrounding this discovery which has been anthropologically interpreted by of various ways. Finally, we will expose how this object ended up on the margins of the history of the prehistoric discipline. Looking at these human remains through the prism of the question of fakes and authenticity in prehistory (Cohen, 1999) will enable us to question the value of this find. La Denise forgery is one of the first case of a fake fossil man, preceding those of Moulin-Quignon and Piltdown.