progressive-evolution theory, which, briefly stated, is--that articulate
language is the result of an elaboration in the long procession of ages in
which there occurred three stages--the cry, vocalisation, and articulation.
The cry is the primordial, pure animal language; it is a simple vocal
aspiration without articulation; it is either a reflex expressing needs and
emotions, or at a higher stage intentional (to call, warn, menace, etc.).
Vocalisation (emission of vowels) is a natural production of the vocal
instrument, and does not in itself contain the essential elements of
speech. Many animals are capable of vocalisation, and in the child the
utterance of vowel sounds is the next stage after the cry.

The conditions necessary to the existence of speech arose with
articulation, and it is intelligence that has converted the vocal
instrument into the speaking instrument. For whereas correct intonation
depends upon the innate musical ear, which is able to control and regulate
the tensions of the minute muscles acting upon the vocal cords, it is
intelligence which alters and changes the form of the resonator by means of
movement of the lips, tongue, and jaw in the production of articulate
speech. The simple musical instrument in the production of phonation is
bilaterally represented in the brain, but as a speaking instrument it is
unilaterally represented in right-handed individuals in the left hemisphere
and in left-handed individuals in the right hemisphere. The reason for this
we shall consider later; but the fact supports Darwin's hypothesis.

Another hypothesis which was brought forward by Grieger and supported by
some authors is summarised by Ribot as follows: "Words are an imitation of
the movements of the mouth. The predominant sense in man is that of sight;
man is pre-eminently visual. Prior to the acquisition of speech he
communicated with his fellows by the aid of gestures and movement of the
mouth and face; he appealed to their eyes. Their facial 'grimaces,'