Journal of Historical Linguistics - Volume 9, Issue 1, 2019

Recent applications of phylogenetic methods to historical linguistics have been criticized for assuming a tree structure in which ancestral languages differentiate and split up into daughter languages, while language evolution is inherently non-tree-like (François 2014; Blench 2015: 32–33). This article attempts to contribute to this debate by discussing the use of the multiple topologies method (Pagel & Meade 2006a) implemented in BayesPhylogenies (Pagel & Meade 2004). This method is applied to lexical datasets from four different language families: Austronesian (Gray, Drummond & Greenhill 2009), Sinitic (Ben Hamed & Wang 2006), Indo-European (Bouckaert et al. 2012), and Japonic (Lee & Hasegawa 2011). Evidence for multiple topologies is found in all families except, surprisingly, Austronesian. It is suggested that reticulation may arise from a number of processes, including dialect chain break-up, borrowing (both shortly after language splits and later on), incomplete lineage sorting, and characteristics of lexical datasets. It is shown that the multiple topologies method is a useful tool to study the dynamics of language evolution.

This paper deals with the historical relations between dialects of Boni, a Cushitic language of Kenya and Somalia. Boni forms the subject of Volume 10 of the Language and Dialect Atlas of Kenya (Heine & Möhlig 1982). Heine presents evidence for three subgroups within Boni, as well as several areas of convergence between dialects belonging to different proposed subgroups. In reviewing his evidence, I find that two of the three splits are not supported by the data, and therefore his conclusions on convergence must also be reinterpreted. Given the presence of numerous intersecting isoglosses, the tree diagram is an inappropriate model for describing the relations between Boni dialects, and I turn to Historical Glottometry (Kalyan & François 2018) to provide a visualization of the data.

Historical Glottometry is a method, recently proposed by Kalyan and François (François 2014; Kalyan & François 2018), for analyzing and representing the relationships among sister languages in a language family. We present a glottometric analysis of the Sogeram language family of Papua New Guinea and, in the process, provide an evaluation of the method. We focus on three topics that we regard as problematic: how to handle the higher incidence of cross-cutting isoglosses in the Sogeram data; how best to handle lexical innovations; and what to do when the data do not allow the analyst to be sure whether a given language underwent a given innovation or not. For each topic we compare different ways of coding and calculating the data and suggest the best way forward. We conclude by proposing changes to the way glottometric data are coded and calculated and the way glottometric results are visualized. We also discuss how to incorporate Historical Glottometry into an effective historical-linguistic research workflow.

Skepticism regarding the tree model has a long tradition in historical linguistics. Although scholars have emphasized that the tree model and its long-standing counterpart, the wave theory, are not necessarily incompatible, the opinion that family trees are unrealistic and should be completely abandoned in the field of historical linguistics has always enjoyed a certain popularity. This skepticism has further increased with the advent of recently proposed techniques for data visualization which seem to confirm that we can study language history without trees. In this article, we show that the concrete arguments that have been brought up in favor of achronistic wave models do not hold. By comparing the phenomenon of incomplete lineage sorting in biology with processes in linguistics, we show that data which do not seem as though they can be explained using trees can indeed be explained without turning to diffusion as an explanation. At the same time, methodological limits in historical reconstruction might easily lead to an overestimation of regularity, which may in turn appear as conflicting patterns when the researcher is trying to reconstruct a coherent phylogeny. We illustrate how, in several instances, trees can benefit language comparison, although we also discuss their shortcomings in modeling mixed languages. While acknowledging that not all aspects of language history are tree-like, and that integrated models which capture both vertical and lateral language relations may depict language history more realistically than trees do, we conclude that all models claiming that vertical language relations can be completely ignored are essentially wrong: either they still tacitly draw upon family trees or they only provide a static display of data and thus fail to model temporal aspects of language history.