It is well-known that the Albanian dialectal map was shaped mainly in Ottoman times, more specifically in the course of the 16th – 18th centuries. Nevertheless, some important linguistic features distinguish Gheg and Tosk zones which belong to the much earlier period of the second half of the first millennium C.E. Did the initial Tosk-Gheg dialect division arise in the area currently inhabited by Gheg and Tosk speakers? Did the (ancestors of) Ghegs and Tosks have contacts without significant interruptions since the time of this division? These and many other questions which may be posed in this regard have been discussed in the literature, but still remain unresolved. In our lecture we shall try to throw some light on these questions using the following quantitative methods of linguistic research: the measuring of linguistic complexity in the modern Albanian dialects; the dialectometric study of the dialects’ closeness based on their phonological and grammatical innovations; the quantitative study of lexical isoglosses including loanwords of different origin and chronological depth.