Dedicated gestures and the emergence of sign language

Sign languages make use of the two hands, facial features, the head, and the body to produce multifaceted gestures that are dedicated for linguistic functions. In a newly emerging sign language - Al-Sayyid Bedouin Sign Language - the appearance of dedicated gestures across four age groups or strata reveals that this remarkable gestural complexity is not available at the outset. Starting with only the hands in Stratum I, each additional articulator is liberated from the rest of the body to perform grammatical functions as the language matures, resulting in ever increasing grammatical complexity. The emergence of dedicated gesture in a new language provides a novel context for addressing questions about the relationship between the physical transmission system and grammar and about linguistic complexity in human language generally.