Caucasia has long played a major role as a link between Europe and Asia, and through it the culture of ancient Mesopotamia spread northward. Indigenous cultures also arose; Transcaucasia was one of the most ancient centres of bronze working from the first half of the 2nd millennium BC. Autochthonous peoples of the Caucasus are mentioned by Herodotus and by later writers such as Strabo.
In the centuries between pre-classical antiquity and the 14th century AD, Caucasia underwent successive invasions by various peoples, including Scythians, Alani, Huns, Khazars, Arabs, Seljuq Turks, and Mongols. Contacts were also maintained with the Mediterranean world.
This history of invasions and distant contacts has left its imprint on the culture of the peoples of Transcaucasia. Middle Eastern influences, in particular, disseminated Iranian languages on the one hand and Christian and Islamic religion on the other. The later history, beginning with a long period of rivalry between Ottoman Turkey and Iran, is marked by the advance of Russian culture, which penetrated farther and farther into Caucasia from the 16th century onward. Throughout this process, individual ethnic groups, under pressure from stronger neighbours, took refuge in the ravines of the mountain ranges to preserve themselves in isolation.
More than 50 different peoples inhabit Transcaucasia; these groups have cultures extending back to ancient times. Since antiquity the Caucasus has been known for its large number of distinct languages; Arab geographers called the region Jabal Al-Alsun ("Mountain of Language").
Several language families are represented in the region. Of the Indo-European languages, Armenian (which is the official language of Armenia) has the greatest number of speakers. Greek is spoken in parts of southern Georgia, and several languages of the Indo-Iranian branch of Indo-European are also spoken. The latter consist of Ossetic (spoken in central Georgia), Talysh (spoken in far southeastern Azerbaijan, on the Caspian Sea), Kurdish (spoken in scattered areas in Armenia and southern Georgia), and Tat (spoken in northeastern Azerbaijan).
Azerbaijani (also called Azeri) is a member of the Turkic branch of Altaic languages and has the largest number of speakers of any of the languages of Transcaucasia. Another Turkic language, Anatolian Turkish, is spoken in a few communities in Azerbaijan.
The rest of the languages spoken in the region are classified as Caucasian languages, which fall into three typologically well-defined families: the Abkhazo-Adyghian, or Northwest, Caucasian languages; the Nakho-Dagestanian, or Northeast, languages; and the Kartvelian, or South Caucasian, languages.
A genetic relationship between the Northeast and Northwest languages seems probable, but the absence of regular sound correspondences between North and South Caucasian languages strongly suggests that the two northern divisions form a family separate from the southern group.
Abkhaz, numerically the most important Abkhazo-Adyghian language of Transcaucasia, is spoken chiefly in Abkhazia; and Abaza, which is closely related to Abkhaz, is spoken along a portion of the coast of the Georgian republic of Adjaria.
The Nakho-Dagestanian languages are a complex group, sometimes subdivided into Nakh, or Central, languages and Dagestanian, or East Caucasian, languages. The only Nakh language of Transcaucasia is Bats, an unwritten language with only a few thousand speakers in north-central Georgia. The Dagestanian languages spoken in this region are Lezgian, Avar, Kryz, Udi, Khinalug, and Budukh, all but Avar being categorized as Lezgian languages.
Chief among the Kartvelian languages is Georgian, which has the largest number of speakers of any Caucasian language. The Georgian language is also distinguished by a literary tradition that dates to the 5th century AD. The other Kartvelian languages are Mingrelian, Laz, and Svan, each of which is spoken mainly in Georgia.