The Talysh are the remnant of an ancient Caucasian aboriginal population that spoke a language close to Old Azeri; This language is perhaps the "Hyrcanian" of the ancient sources (Strabo). A large number of Talysh were subject to Turkicization (i.e., assimilation into the Azeri Turkish culture) from the early Middle Ages. The Talysh established a khanate in the seventeenth century, following the fall of the empire of Nadir Shah. The founder of the khanate's dynasty was Seid Abbas, by birth a Talysh noble. In 1785 the Talysh Khanate became a dependency of Fatali, the Kuban khan, after whose death (1789) the Talysh Khanate regained its independence. The Talysh Khanate was joined to Russia initially by the Gulistan Treaty and finally by the Turkmenchay Agreement in 1828. Unification with Russia may have served to hinder the complete assimilation of the Talysh into their Turkic-speaking environment.