This paper proposes a bio-cultural theory of presence based on four different positions related to the role and structure of presence, as follows. First, presence is a defining feature of self and it is related to the evolution of a key feature of any central nervous system: the embedding of sensory-referred properties into an internal functional space. Without the emergence of the sense of presence it is impossible for the nervous system to experience distal attribution: the referencing of our perception to an external space beyond the limits of the sensory organs themselves. Second, even if the experience of the sense of presence is a unitary feeling, conceptually it can be divided in three different layers, phylogenetically different and strictly related to the three levels of self identified by Damasio. In particular we can make conceptual distinctions between proto presence (self vs. non self), core presence (self vs. present external world), and extended presence (self relative to present external world). Third, given that each layer of presence solves a particular facet of the internal/external world separation, it is characterized by specific properties. Finally, in humans the sense of presence is a direct function of these three layers: the more they are integrated, the more we are present. In the experience of optimal presence, biologically and culturally determined cognitive processes are working in harmony--to focus all levels of the self on a significant situation in the external world, whether this is real or virtual.