The authors and artists of the last decades of the 19th century show an obvious eschatological obsession, whether it concerns the decline of the nation, of civilization, or of humanity as a whole. This anxiety is declined in a poetics and an aesthetic of finitude that "decadence" designates as a word-totem. However, this fin-de-siecle, which believes itself to be the end of everything, draws from new knowledge about origins (prehistory, evolutionism) the ferments of its apocalyptic visions. In this study, it will be a question of understanding the implication of knowledge on the beginnings of time in the imaginary of the end of time. Because, once this culture positions itself on the scale of the species that this new knowledge invites us to think about, it would seem that dying is not so much "leaving a lot", to take up the pleasant line of Alphonse Allais, it is perhaps and above all to return.