The Caucasian languages contribute highly to the linguistic diversity of Europe. Many of the languages spoken in the region are rather small, especially in Dagestan, with less than 5-10,000 speakers, for instance, Archi (1200), Hinukh (550), Hunzib (1849). You may see some of the statistics in the Ethnologue database (Armenia, Azerbaijan, Georgia, Russia). The Red book of the peoples of the Russian Empire (link) provides more information on the genetic affiliation of the languages, population statistics, the history, economy and religion of the peoples as well as some information on research conducted on the language.
A number of the languages spoken in the Caucasus are endangered to a greater or lesser degree. That a language is endangered means that there has been a decline in use, especially when the language is not transmitted to children. The gradual decline eventually leads to language loss and death; that the language becomes extinct. Why is it important to maintain the multitude of languages? See Barbara Grimes for a general overview of issues related to language endangerment.
The map above shows Unesco data on the Caucasus. Unesco offers an interactive site on the world's linguistic endangerment: http://www.unesco.org/languages-atlas/index.php
Ubykh is one of the Caucasian languages that is extinct. The Ubykhs originate from Black Sea coast, Sochi region (marked by a black pin on the map). The last speaker of the language Tevfik Esenç died in Turkey in 1992 (read more about Tevfik Esenç and Ubykh). In the video clip below (in French) you see the French linguist (of Georgian descent) Georges Charachidzé telling about his fieldwork with the last speaker Tevfik Esenç, including audio and video recordings (you can listen to more Ubykh here at the Lacito database: http://lacito.vjf.cnrs.fr/archivage/languages/Ubykh.htm).
A highly endangered language in Georgia is Tsova-tush (Batsbi), spoken actively by approximately 300 in the village of Zemo-Alvani (the song in the video clip below is in Tsova-tush):
Transcriptions of the Caucasian languages are complex, as they have to represent the unusually large inventories of phonemes (distinctive sounds) in these languages. As in native Georgian, the sound system does not only include, for instance, p, t, k (as in English), but distinguish between plain and glottalized consonants as in p p', t t', k k'. In the Northwest Caucasian languages the system is even more complex adding the feature of labialisation to some consonants (as in Adyghe t, t', t'w).
The basic sentence structure of Caucasian languages differs from the pattern that is common in many European languages. We find so-called ergative structures in approximately in a quarter of the world's languages. Apart from the Caucasian languages such structures appear in, for instance, Basque, Eskimo languages, Australian and Amerindan languages. What is meant by "ergative sructures"? We have to look at both at sentences with intransitive and transitive verbs in order to explain this. Intranstiive verbs involve states or actions that are limited to one participant; the subject. This is opposed to transitives in which verbs describe situations with two participants: one person (Subject) who is performing an action that in some way affects or is directed towards another person or object (Direct object).
Recommended Literature:
Barbara F. Grimes: Global Language Viability. Causes, Symptoms and Cures for Endangered Languages
Catford, J.C. 1977. Mountain of Tongues: The Languages of the Caucasus Annual Review of Anthropology, Vol. 6, (1977), pp. 283-314
Grenoble, Lenore A. 2003 Language Policy in the Soviet Union Kluwer Academic Publishers
Pereltsvaig, Asya, 2010. Obituary: The Ubykh Language, The Languages of the World.
Vamling, K. The Endangered Languages of the World and the Case of Adyghe-Abkhaz Languages Ankara
«Unesco offers an interactive site on the world's linguistic endangerment»
There is a project dedicated to saving endangered languages. And they also have an interactive map of them. I hope it will be interesting for you as a person who likes language issues: https://steemit.com/culture/@axbezzub/endangered-languages-an-interactive-map