4.2 How Do We Learn Language?

The human anatomy that allowed the development of language emerged six to seven million years ago when the first human ancestors became bipedal—habitually walking on two feet. Most other mammals are quadrupedal—they move about on four feet. This evolutionary development freed up the forelimbs of human ancestors for other activities, such as carrying items and doing more and more complex things with their hands. It also started a chain of anatomical adaptations. One adaptation was a change in the way the skull was placed on the spine. The skull of quadrupedal animals is attached to the spine at the back of the skull because the head is thrust forward. With the new upright bipedal position of pre-humans, the attachment to the spine moved toward the center of the base of the skull. This skeletal change in turn brought about changes in the shape and position of the mouth and throat anatomy.

Humans have all the same organs in the mouth and throat that the other great apes have, but the larynx, or voice box (you may know it as the Adam’s apple), is in a lower position in the throat in humans. This creates a longer pharynx, or throat cavity, which functions as a resonating and amplifying chamber for the speech sounds emitted by the larynx. The rounding of the shape of the tongue and palate, or the roof of the mouth, enables humans to make a greater variety of sounds than any great ape is capable of making.

Speech is produced by exhaling air from the lungs, which passes through the larynx. The voice is created by the vibration of the vocal folds in the larynx when they are pulled tightly together, leaving a narrow slit for the air to pass through under pressure. The narrower the slit, the higher the pitch of the sound produced. The sound waves in the exhaled air pass through the pharynx then out through the mouth and/or the nose. The different positions and movements of the articulators—the tongue, the lips, the jaw—produce the different speech sounds.

Along with the changes in mouth and throat anatomy that made speech possible came a gradual enlargement and compartmentalization of the brain of human ancestors over millions of years. The modern human brain is among the largest, in proportion to body size, of all animals. This development was crucial to language ability because a tremendous amount of brain power is required to process, store, produce, and comprehend the complex system of any human language and its associated culture. In addition, two areas in the left brain are specifically dedicated to the processing of language; no other species has them. They are Broca’s area in the left frontal lobe near the temple, and Wernicke’s area, in the temporal lobe just behind the left ear.