Mammals have two olfactory organs: the olfactory mucus and the vomeronasal organ, which was discovered at the beginning of the nineteenth century. For long, it was believed that the latter did not serve any purpose in humans. Then in 1949, certain substances were discovered, at first in insects, which could act on the vomeronasal organ by direct contact. Known as pheromones, these substances are regarded as essential for communication between animals of certain species. Since 1970, it has been known that they play a vital role in human sexual desire and in the control of reproduction.
Claude Aron explains that the olfactory attraction between sexual partners is a universal phenomenon, even if its role among humans is more limited than among other mammals. In animal species the role of pheromones has not been curbed by centuries of social conditioning. Olfactory attraction functions regardless of the gender of the sexual partners — which raises the question: Are pheromones proof of our “natural” bisexuality?

Claude Aron, a specialist in reproductive physiology, is an honorary professor at the University Louis-Pasteur in Strasbourg. He is the author of La Bisexualité et l’ordre de la nature.