The human larynx or “voice box” (containing the vocal folds or vocal cords) differs
significantly in position from the larynx of other primates such as monkeys. In the
course of human physical development, the assumption of an upright posture moved
the head more directly above the spinal column and the larynx dropped to a lower
position. This created a longer cavity called the pharynx, above the vocal folds, which
acts as a resonator for increased range and clarity of the sounds produced via the
larynx and the vocal tract. One unfortunate consequence of this development is that
the lower position of the human larynx makes it much more possible for the human to
choke on pieces of food. Monkeys may not be able to use their larynx to produce
speech sounds, but they do not suffer from the problem of getting food stuck in their
windpipe. In evolutionary terms, there must have been a big advantage in getting this
extra vocal power (i.e. a larger range of sound distinctions) to outweigh the potential
disadvantage from an increased risk of choking to death.