Scent has a language all its own, which is why it evokes such deep memories in us. The tendrils of scent’s patois reach into the primitive, emotional part of our minds. This explains why the odour of diesel fuel picks the author up and plops him down in a train station, where he’s waiting for his grandmother to arrive. It just so happens that fragrances are the Dr. Jekyll and Mr. Hyde of nature because the same aroma can either attract or repel. The difference lies in strength. At high potency, some combinations remind us of an outhouse, yet at a lower level the same combination smells like violets. Pheromones are of particular interest. For pheromones are chemical body language; they are invisible to the eye, but instantly signal our noses, changing our physical responses and our behaviou...