Published online by Cambridge University Press: 20 January 2010
What was the interplay of biological and cultural evolution in yielding modern humans with their rich, flexible, and diverse languages? What has biological evolution contributed to the innate capabilities of the human brain that allow human children to master language and how has society evolved to develop those capabilities? I approach these questions through analysis of the recent development of two new sign languages: Nicaraguan Sign Language (NSL), which developed in just 25 years within a community of deaf Nicaraguans, and Al-Sayyid Bedouin Sign Language (ABSL), which developed over a period of at most 70 years in a community of deaf and speaking Bedouin. Understanding the tradeoff between innate capabilities and social influences in the emergence of NSL and ABSL will ground an understanding of how these modern social influences may differ from those available to early humans at the dawn of language.
The mirror system hypothesis (MSH) is a specific theory of the evolution of the human “language-ready brain.” It is informed by the view that language is a multimodal system of production and performance that involves voice, hands, and face. Speaking humans accompany their speech with facial expressions and cospeech gestures of the hands (Kendon, 2004; McNeill, 1992, 2005), while many deaf people employ signed languages that are very different from spoken languages – with specific signs (which may integrate arm, hand, and face movements) that are part of a conventionalized system with limited resemblance to cospeech gestures. Details of MSH are set forth in Arbib (2005a, developing the insights of Arbib and Rizzolatti, 1997; Rizzolatti and Arbib, 1998), with commentaries and a response.