Linguistic phylogenies are standardly inferred from lexical cognate relationships (e.g., Bouckaert et al. 2012, Chang et al. 2015, Sagart et al. 2019). Despite the prevalence of this practice, it suffers from well-known drawbacks. First, it disregards the phylogenetic signal that exists in the form of the words themselves. Second, it limits the modeling possibilities since it relies on an arbitrary coding of the data. In this talk, I introduce a novel framework for linguistic phylogenetics that overcomes both of these shortcomings. The heart of this framework is the TKF91 model (Thorne et al. 1991), which allows phylogenetic inference to be carried out directly from cognate word-forms. This model not only opens up a new horizon in the study of linguistic phylogenetics, but allows historical linguists to investigate questions of sound change that were previously out of reach.

Divergence-time estimation is one of the most important endeavors in historical linguistics. Its importance is matched only by its difficulty. As Bayesian methods of divergence-time estimation have become more common over the past two decades, a number of critical issues have come to the fore, including model sensitivity, the dependence of root-age estimates on uncertain interior-node ages, and the relationship between ancient languages and their modern counterparts. This study addresses these issues in an investigation of a particularly fraught case within Indo-European, the diversification of Latin into the Romance languages. The results of this study support a gradualist account of their formation that most likely begins after 300 CE. They also bolster the view that Classical Latin is a sampled ancestor of the Romance languages (i.e., it lies along the branch leading to the Romance languages).

Grammaticalization is characterized by robust directional asymmetries (e.g., Kuteva et al. 2019). For instance, body-part nominals develop into spatial adpositions, minimizers develop into negation markers, and subject pronouns become agreement markers. Changes in the opposite direction are either rare or unattested (Garrett 2012:52). Such robust cross-linguistic asymmetries have led some scholars to reify grammaticalization trajectories as universal mechanistic forces (Heath 1998:729). One consequence of such a view is that the ambient morphosyntax of a language has little or even no relevance for grammaticalization. This paper uses Bayesian phylogenetic methods to demonstrate the critical role that pre-existing morphosyntax can play in grammaticalization. The empirical basis for this claim is the grammaticalization of definite and indefinite articles in the history of Indo-European: indefinite articles developed at a faster rate among languages in which a definite article had already emerged compared to those lacking a definite article. The two changes are thus correlated. The results of this case study suggest that there is much more to be learned about when and why grammaticalization occurs by investigating its relationship to the pre-existing linguistic system (cf. Reinöhl and Himmelmann 2017:381).