Our greatest weakness, however, is our pitifully small sense of taste and smell. Over 99 percent of all living species, from microorganisms to animals, rely on chemical senses to find their way through the environment. They have also perfected the capacity to communicate with one another with special chemicals called pheromones. In contrast, human beings, along with monkeys, apes, and birds, are among the rare life forms that are primarily audiovisual, and correspondingly weak in taste and smell. We are idiots compared with rattlesnakes and bloodhounds. Our poor ability to smell and taste is reflected in the small size of our chemosensory vocabularies, forcing us for the most part to fall back on similes and other forms of metaphor. A wine has a delicate bouquet, we say, its taste is full and somewhat fruity. A scent is like that of a rose, or pine, or rain newly fallen on the earth.