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Though we tend to think of spoken language as a key aspect of our humanness, it is striking that our bodies appear to contain no structures that are used uniquely for speech. In fact, every component of the human vocal apparatus exists because of its role in some more basic, survival‐oriented function. Our “organs of speech” therefore illustrate an evolutionary phenomenon called EXAPTATION: the recruitment of old structures for new purposes. Several examples are given in Table 2.1. The lungs, for instance, which initiate the airflow for most speech, are essential for the life‐supporting function of pulmonary ventilation (breathing). The teeth and tongue, which we use to articulate many speech sounds, are needed for mastication (chewing) and—along with parts of the LARYNX—for deglutition (swallowing). Olfaction (smelling) occurs through structures in the NASAL CAVITY, which also happens to allow production of speech sounds like the /m/ in mouth. Together, structures of the nose and tongue make gustation (tasting) possible. And the VOCAL FOLDS (popularly known as the vocal cords) help guard the TRACHEA (windpipe) from food and liquids that might pose serious problems should they enter the lungs. All these parts of the vocal tract exist in many non‐human—and therefore non‐speaking—animals, so they are clearly not specific to speech.

The term exaptation was coined by Stephen Jay Gould and Elisabeth Vrba, two American paleontologists who studied how traits and structures often develop new functions that differ from their original ones.

Table 2.1 Exapted Structures Used for Speech

Primary Function	Structures	Role in Speech
Pulmonary ventilation	Lungs, trachea, pharynx, nasal cavity, oral cavity	Initiation and conduction of airstream for generation of speech sounds
Mastication	Tongue, teeth	Speech articulation, phonation
Deglutition	Tongue, velum, uvula, pharynx, larynx
Gustation	Tongue, nasal cavity
Olfaction	Nasal cavity	Production of nasal sounds, like the /m/ in mouth