by elongating the nose, protruding the lips, or by lowering the larynx in the
throat. Recent cineradiographic observations of vocalizing mammals reveal
that in dogs, cotton-top tamarins, pigs, goats, and deer the larynx is lowered
during vocalization (Fitch 2000a; Fitch and Reby 2001). During resting
breathing in mammals, the larynx is inserted into the nasopharynx. The
epiglottis engages with the velum, forming a tight seal, which separates the
nasal/tracheal passageway for air and the oral/esophageal passageway for
food.This allows many mammals to breathe and swallow liquids at the same
time and is probably particularly important for young mammals, allowing
them to suckle (orally) and breathe (nasally) simultaneously. For many
years, it was thought that an intranarial larynx was the only normal position in nonhuman mammals, but the cineradiographic data indicate that in
fact a lowering of the larynx during calling is typical for these mammals.
This descent may subserve the production of high-amplitude calls because
the nasal passageways absorb sound much more than the oral cavity,
decreasing the amplitude of nasal calls by about 15 dB relative to oral calls
(Fitch 2000a).
Another form of laryngeal descent is permanent descent of the larynx.
Rather than being dynamically disengaged from the nasopharynx during
calling and then reinserted, the larynx is permanently lowered. This is the
situation in humans. Although human babies start life with an intranarial
larynx and can suckle and breathe simultaneously like other neonatal
mammals, the larynx begins to descend caudally starting around 3 months
of age. This gives humans an unusually long pharynx, which is believed to
subserve the production of a wider range of vocal tract shapes, and thus
vowel formant frequencies, than attainable by other mammals (Lieberman
et al. 1969; Lieberman 1984; Crelin 1987). Recent data show that there is in
fact a second “descent of the larynx” in humans at puberty, limited to males,
in which the larynx descends another several centimeters relative to females
(Fitch and Giedd 1999). Because adult males are not superior in speech
abilities to females (indeed, available evidence suggests the opposite:
Koenigsknecht and Friedman 1976; Kimura 1983; Henton 1992), this observation suggests that the function of the elongated vocal tract in humans may
not be limited to its effects on the vowel space.
Although the descended larynx has long been thought to be a uniquely
human feature, a similar descent of the larynx is seen in several species of
Eurasian deer, including fallow (Dama dama) and red (Cervus elaphus)
deer (Fitch and Reby 2001). In parallel with adult male humans, the larynx
in adult males of these deer species is enlarged relative to juveniles or
females and rests much lower in the throat. During roar vocalizations
produced during the rutting period, powerfully developed sternothyroid
muscles pull the larynx even lower, until it reaches the sternum in large
males. As predicted by acoustic theory, time-synched audiovisual analysis
shows that formant frequencies drop as the larynx descends, due to the
elongation of the vocal tract.
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W.T. Fitch and M.D. Hauser
throat. Recent cineradiographic observations of vocalizing mammals reveal
that in dogs, cotton-top tamarins, pigs, goats, and deer the larynx is lowered
during vocalization (Fitch 2000a; Fitch and Reby 2001). During resting
breathing in mammals, the larynx is inserted into the nasopharynx. The
epiglottis engages with the velum, forming a tight seal, which separates the
nasal/tracheal passageway for air and the oral/esophageal passageway for
food.This allows many mammals to breathe and swallow liquids at the same
time and is probably particularly important for young mammals, allowing
them to suckle (orally) and breathe (nasally) simultaneously. For many
years, it was thought that an intranarial larynx was the only normal position in nonhuman mammals, but the cineradiographic data indicate that in
fact a lowering of the larynx during calling is typical for these mammals.
This descent may subserve the production of high-amplitude calls because
the nasal passageways absorb sound much more than the oral cavity,
decreasing the amplitude of nasal calls by about 15 dB relative to oral calls
(Fitch 2000a).
Another form of laryngeal descent is permanent descent of the larynx.
Rather than being dynamically disengaged from the nasopharynx during
calling and then reinserted, the larynx is permanently lowered. This is the
situation in humans. Although human babies start life with an intranarial
larynx and can suckle and breathe simultaneously like other neonatal
mammals, the larynx begins to descend caudally starting around 3 months
of age. This gives humans an unusually long pharynx, which is believed to
subserve the production of a wider range of vocal tract shapes, and thus
vowel formant frequencies, than attainable by other mammals (Lieberman
et al. 1969; Lieberman 1984; Crelin 1987). Recent data show that there is in
fact a second “descent of the larynx” in humans at puberty, limited to males,
in which the larynx descends another several centimeters relative to females
(Fitch and Giedd 1999). Because adult males are not superior in speech
abilities to females (indeed, available evidence suggests the opposite:
Koenigsknecht and Friedman 1976; Kimura 1983; Henton 1992), this observation suggests that the function of the elongated vocal tract in humans may
not be limited to its effects on the vowel space.
Although the descended larynx has long been thought to be a uniquely
human feature, a similar descent of the larynx is seen in several species of
Eurasian deer, including fallow (Dama dama) and red (Cervus elaphus)
deer (Fitch and Reby 2001). In parallel with adult male humans, the larynx
in adult males of these deer species is enlarged relative to juveniles or
females and rests much lower in the throat. During roar vocalizations
produced during the rutting period, powerfully developed sternothyroid
muscles pull the larynx even lower, until it reaches the sternum in large
males. As predicted by acoustic theory, time-synched audiovisual analysis
shows that formant frequencies drop as the larynx descends, due to the
elongation of the vocal tract.
92
W.T. Fitch and M.D. Hauser