<Li> Our ancestors started to use more and more tools, meaning that their hands were occupied and could no longer be used for gesturing . </Li> <Li> Manual gesturing requires that speakers and listeners be visible to one another . In many situations, they might need to communicate, even without visual contact--for example after nightfall or when foliage obstructs visibility . </Li> <Li> A composite hypothesis holds that early language took the form of part gestural and part vocal mimesis (imitative' song - and - dance'), combining modalities because all signals (like those of nonhuman apes and monkeys) still needed to be costly in order to be intrinsically convincing . In that event, each multi-media display would have needed not just to disambiguate an intended meaning but also to inspire confidence in the signal's reliability . The suggestion is that only once community - wide contractual understandings had come into force could trust in communicative intentions be automatically assumed, at last allowing Homo sapiens to shift to a more efficient default format . Since vocal distinctive features (sound contrasts) are ideal for this purpose, it was only at this point--when intrinsically persuasive body - language was no longer required to convey each message--that the decisive shift from manual gesture to our current primary reliance on spoken language occurred . </Li> <P> A comparable hypothesis states that in' articulate' language, gesture and vocalisation are intrinsically linked, as language evolved from equally intrinsically linked dance and song . Humans still use manual and facial gestures when they speak, especially when people meet who have no language in common . There are also, of course, a great number of sign languages still in existence, commonly associated with deaf communities . These sign languages are equal in complexity, sophistication, and expressive power, to any oral language . The cognitive functions are similar and the parts of the brain used are similar . The main difference is that the "phonemes" are produced on the outside of the body, articulated with hands, body, and facial expression, rather than inside the body articulated with tongue, teeth, lips, and breathing . (Compare the motor theory of speech perception .) </P>

Historical beginning of language according to chronology based on the text