Astonishingly, the human nose can detect 1 trillion odors, including many we don’t even realize we are detecting. It’s well known that women living together in dorm rooms are able to synchronize their menstrual cycles; the reason is they are nasally detecting each other’s pheromones. Women may have a keener sense of smell than men, and it sharpens during pregnancy, when they must be alert to subtle hazards.
