Historical Linguistics of Sign Languages: Progress and Problems

The historical demography of the Martha's Vineyard signing community

The deaf population of Martha's Vineyard has fascinated scholars for more than a century since Alexander Graham Bell's research on the frequent occurrence of deafness there and since Groce's book on the island's signing community (Groce, N. E. (1985). Everyone here spoke sign language: Hereditary deafness on Martha's Vineyard. Cambridge, MA: Harvard University Press.). In Groce's work, and in that of subsequent scholars, the Vineyard signing community has often been portrayed as remote and outlying, having developed independently of mainland signing communities for roughly 133 years until 1825. We re-examine that interpretation in light of historical, demographic, and genealogical evidence covering the period 1692-2008. We argue that the Vineyard signing community began in Chilmark in 1785, 93 years later than previously thought, and that it had had a brief period of independent development, roughly 40 years, before becoming well connected, through deaf education, to the nascent New England signing community. We consider the implications of the Vineyard community's history for our understanding of how village signing communities develop.

Computational phylogenetics reveal histories of sign languages

Sign languages are naturally occurring languages. As such, their emergence and spread reflect the histories of their communities. However, limitations in historical recordkeeping and linguistic documentation have hindered the diachronic analysis of sign languages. In this work, we used computational phylogenetic methods to study family structure among 19 sign languages from deaf communities worldwide. We used phonologically coded lexical data from contemporary languages to infer relatedness and suggest that these methods can help study regular form changes in sign languages. The inferred trees are consistent in key respects with known historical information but challenge certain assumed groupings and surpass analyses made available by traditional methods. Moreover, the phylogenetic inferences are not reducible to geographic distribution but do affirm the importance of geopolitical forces in the histories of human languages.