This research group, under the name of Diachronic Linguistics, Typology and History of the Basque Country, brings together researchers who study the diachronic aspects of languages and the evolution of the phonological and grammatical structure over time. The study of the history and prehistory of the Basque Country occupies an important place. The reserach team is formed around a common theoretical and methodological basis, which builds on principles of historical linguistics and linguistic typology, the latter being applied mainly in a diachronic perspective. This shared view appears in the study of several topics:

1) the history and prehistory of the Basque language,
2) Paleohispanic languages,
3) the evolution of morphological and syntactic constructions in different languages from a typological point of view.

1. The history and prehistory of the Basque language covers both external and internal aspects, within a comprehensive approach that includes the reconstruction of the Proto-Basque language, the emergence of modern literary dialects and the establishment of a unified Basque (the Batua), paying heed to different periods of the language (Vasconic and Aquitanian, Medieval Basque, archaic, classical and modern periods). A rigorous history of language must necessarily be established on a philologically sound knowledge of the texts throughout history. Hence one of the main tasks of the group is also the critical edition of the archaic and classical texts written in Basque (until the 19th century), as well as of all secondary materials, especially the rich medieval toponomastics of Latin and Romance cartularies.

2. Basque, as the only language surviving from the Roman era of the Iberian Peninsula, has always been taken into account in the study of the ancient Hispanic languages. The second field of study consists of Paleohispanic languages and epigraphies, a set of linguistic data of very different sociolinguistic and documentary origins and circumstances. The Paleohispanic texts are preserved in some original writing systems, not always well deciphered; their testimony is fragmented, and therefore our knowledge of their grammar is partial. The group works in the digital edition of many of these inscriptions, especially in the Iberian inscriptions from Narbonense and Levante provinces, in the Celtiberian ones, and in the study of personal onomastics and theonymy as the only material preserved in vast areas of the peninsula. This combination of data serves to establish distinct linguistic areas and to classify the Paleohispanic languages and dialects. Lately, the field of research has been extended to cover the Gaulish onomastics.

3. Studies of diachronic typology focus on the study of the evolution of certain morphological and syntactic constructions and concentrate on such topics as (i) the grammaticalization of the expression of animation, a semantic category with different effects on languages; (ii) changes in the morphological strategy or technique; (iii) the relationship between language contact and the evolution of systems like the grammatical gender; (iv) diachronic asymmetries between main and subordinate sentences; (v) morphosyntactic change in the development of the mechanisms of subordination; and (vi) the transversality of grammatical features such as tense, aspect, mood, case and person, which can be differently realized in different languages. Typologically based diachronic analysis is an essential tool for understanding the patterns of language change, and is therefore particularly useful in reconstructing unattested processes of change corresponding to the prehistory of languages, in which, as in the case of the Basque language, it is not possible to apply other techniques (e.g., the comparative method beyond its dialects).