The value of "triangulation" in determining phylogenetic relationship: on the areal and genetic connections of the Berta languages
In this paper, I argue against a recent attempt at re-classifying the small group of Berta languages, spoken in Ethiopia, as being closely related to the geographically adjacent East Jebel group, based on numerous lexical similarities between the two taxa. It is suggested that the best method to determine if these similarities are due to common genetic descent or intense contact is to "triangulate" the lexical data by introducing another possible linguistic relative into the comparison. A simple lexicostatistical test shows that the Jebel languages show at least as strong a link with Nilotic languages as they do with Berta, while Berta and Nilotic, on the contrary, have very little in common. This is a significant argument that Jebel languages belong together with Nilotic in the East Sudanic family, while most of the lexical matches between Jebel and Berta are due to the latter’s strong lexical influence on the former.