Current philosophy of biology shows epistemological essential tensions between individual and its "differing", i.e. the presence of inter-individual differences in one and the same population. From a theoretical and historical perspective, we underline the importance of this differing in population genetics, where, in spite of common mathematical tools, conflicting interpretations persist. This paper aims to point out both the fading of unity and the singleness of the "individual" in the light of symbiontic studies and a more enlarged population thinking. From a philosophical point of view, even if lexically unchanged, the notion of individual acquires new epistemic stratified meanings.
Keywords: Epigenetics, hologenome, individual, population thinking, symbionts.