Research on an extended family of Mayan Indians in an isolated community in highland Chiapas, Mexico, has shown that even a tiny community of deaf individuals who have no direct contact with any language, spoken or signed, can within a single generation, invent a spontaneous sign language with complex grammar. 

Conducted by an anthropologist at the University of California, San Diego, the research highlights the sorts of social circumstances and communicative resources that make the invention of a new language possible. In this case, a community of signers built on the spontaneous gestures of a hearing community to produce, in less than a generation, a sign language that allows elaborate communication and social interaction.

The anthropologist followed three deaf siblings who grew up together in the Mexican village of Tzotzil, where the Mayan language is spoken. The siblings had no contact with other deaf people and only indirect exposure to the spoken Mayan language via their hearing siblings. Separated in age by 13 years, the siblings turned the simple system of gestures used by the oldest deaf sister into a complex sign language.

The Tzotzil sign language contains grammatical structures found in other established languages, both spoken and signed. The language uses representational gestures and combines them with more abstract elements in a surprisingly elaborate and general way.  For example, a simple noun is normally combined with a more abstract element, called a classifier, to indicate size and shape; it may also be followed by a number. Thus, the sign for "'chicken" involves a stylized pantomime (based on the way villagers typically kill chickens with a sharp jerk to break the animal's neck).  To sign "two chicks" one signs first a size/shape classifier to show the small size, then "chicken," followed by the number "two."