How did language get started? Many support the gestural theory, which claims that sign language is the missing link between the primate communication and human language. These supporters emphasize four reasons:
The human voice-box or larynx is more streamlined than that of other primates; it is also positioned lower than in other primates.
The particular position of the larynx, the complexity of the muscular tongue and the possibility to produce vowels via mouth, allow the human beings to produce three fairly extreme vowels:
