Words that are spoken by the hands alone
Before the earliest human beings learned to speak, they had to communicate with their fellows by means of grunts, cries, facial expressions, and gestures. Even when spoken language developed, however, sign language survived. Highly developed sign languages have been documented in recent times among the aborigines of Australia as well as the Plains Indians of North America.
These systems, employing hundreds of different signs and gestures, allowed speakers of different languages to communicate effectively without recourse to interpreters, and, if necessary, at distances beyond earshot.
In modern societies deep-sea divers, air-traffic controllers, broadcasters, and other occupational groups also have their own specialized vocabularies of gestures, but the only present-day sign languages to substitute completely for speech are those devised in modern times for the speech-and-hearing impaired. For example, nearly a million deaf people in North America are currently using American Sign Language (ASL), supplemented by finger spelling to convey names of people, technical words, and place names.
American Sign Language.Early observers of the Sioux and others who used sign language were astonished at the speed and accuracy with which signers communicated information — more than twice as fast as speech, one man claimed.