The sense of smell plays a crucial role in the sensory world of animals. Two chemosensory systems have been traditionally thought to play-independent roles in mammalian olfaction. According to this, the main olfactory system (MOS) specializes in the detection of environmental odorants, while the vomeronasal system (VNS) senses pheromones and semiochemicals produced by individuals of the same or different species. Although both systems differ in their anatomy and function, recent evidence suggests they act synergistically in the perception of scents. These interactions include similar responses to some ligands, overlap of telencephalic connections and mutual influences in the regulation of olfactory-guided behavior. In the present work, we propose the idea that the relationships between systems observed at the organismic level result from a constant interaction during development and reflects a common history of ecological adaptations in evolution. We review the literature to illustrate examples of developmental and evolutionary processes that evidence these interactions and propose that future research integrating both systems may shed new light on the mechanisms of olfaction.