Q&A: Can We Trace the Evolution of Sign Language?

Image Courtesy of Wannapik Studio.

The use of hand gestures for communication has a long history, dating as far back as 5 B.C.E. in ancient Greece. Despite having existed for a long time, gestural signals, which would eventually become sign languages (SLs), have historically been less well documented than oral languages due to challenges with recording visual gestures and the lack of widely used written systems for SL.

To address this, researchers created a computer program to trace the history of nineteen contemporary SLs. Signs corresponding to the same set of core vocabulary words were taken from each of these languages as the input data. Phonetic parameters and patterns of the signs such as handedness (one- or two-handed signs), handshape, location of the sign, and movement were encoded as metadata to be used for comparison between the languages. 

Using this program, the researchers separated SLs into two independent language families by region: European and Asian. A lack of historical reports corroborated the hypothesis that these two SL families had little to no influence on each other in the past. Some SLs within the European SL family were grouped into subfamilies consistent with geopolitical history, namely the central European subfamily and the Eastern European subfamily with ties to the history of the Russian Empire and the Soviet Union. The Asian SL family consisted of two subfamilies: Japanese/Taiwan and Chinese/Hong Kong SL. As seen above, the use of computational phylogenetic methods only foreshadows the discovery of more connections across the linguistic history of sign language.