Gialluisi, A., Dediu, D., Francks, C., & Fisher, S. E. (2013). Persistence and transmission of recessive deafness and sign language: New insights from village sign languages. European Journal of Human Genetics,21, 894-896. doi:10.1038/ejhg.2012.292.
First paragraph: The study of the transmission of sign languages can give novel insights into the transmission of spoken languages1 and, more generally, into gene–culture coevolution. Over the years, several papers related to the persistence of sign language have been
reported.2–6 All of these studies have emphasized the role of assortative (non-random) mating by deafness state (ie, a tendency for deaf individuals to partner together) for increasing the frequency of recessive deafness, and hence for the persistence of sign language in a population.