What are the reasons of the ethnical fragmentation of the Caucasus?

Question

While investigating on Albania, I kept finding peoples I never heard of before. Notwithstanding my vast ignorance, this was systematic to the point that I started investigating. Take a look at this map: it does not even reproduce all of the ethnic groups. The overabundance is so evident that this question is asked elsewhere on the internet (with no answer, spare that click for later). This website has a comprehensive list of ethnicity, but offers no answers. I was impressed reading:

According to the Roman historian Pliny, when the Romans came to the Caucasus, they needed 134 interpreters to deal with the jumble of languages they found. The 10th century Arab geographer and historian al-Azizi referred to the area as the “mountain of languages”. Today, this relatively small area (about the size of New England) is home not only to over 100 languages, but to four distinct language families that are indigenous and unique to the region: the Northwest Caucasian family, the Northeast Caucasian family, the Nakh family and the South Caucasian (or Kartvelian) family. In addition, several languages from families common elsewhere – Indo-European and Turkic – are spoken by various groups in the Caucasus region as well. Like the linguistic situation, the ethnic situation too presents a complex and highly mosaic picture, because ethnicity correlates closely, though not perfectly, as we shall see below, with the languages.

We know how several (hundreds?) migrations brought people from Central and East Asia towards Europe and the Middle East. Most of these people established their own rule over some land, but it seems to me that invaders either survived to date as an ethnic and/or cultural majority (Hungary, Turkey, Bulgaria, ...) or disappeared as a group - leaving genetic and/or cultural heritage to different degrees (Huns, Lombards, Vikings, ...).

However, when we look at the ethnic map of Europe, there is considerable less fragmentation than in the Caucasus only, especially if one considers the difference in overall extension and population, and that Europe itself contains a fair amount of impervious regions (Alps, Pyrenees, ...)

The question: why so many groups survived (at least culturally) in the Caucasus compared to nearby regions? I'm interested both in geographical reasons and in historical developments (e.g. national states vs empires, political fragmentation vs centralization, ...).

Answer 1

Here's my proposition, basically it's just a set of Caucasus characteristics making this region especially interesting. By which we mean: there're numerous languages, 3 distinct language families, characteristic just for this region.

My first point is, language diversity / fragmentation is normal for regions without a strong state / commerce / any unifying factor. The local societies tend to isolate from each other, hence many different languages emerge (and the isolation is stronger in mountainous realm of valleys, where travelling is simply hard).

Take pre-Columbian America for instance, aboriginal Australia, pre-Roman Italy, or to some extent - even modern European countries, in 18th century Spain, Aragonese, Leonese, Fala, Galician were spoken by significant population (not to mention Basque, Catalan, Valencian and Andalusian). What happened to Aragonese? Integration with Castille, and raise of national state has put this language in danger. What happened to old Italic languages? Rise of Roman state and culture swept them out.

On the other hand, what happened to all these extinct Celtic languages? They were swept by subsequent waves of German and Slavic migrations.

So the reasons for the Caucasus situation in contrast to that of Europe, in my opinion are:

1. Caucasus is far, far away from aggresive empires - so it's easier to persist with local culture / language, you don't get immigrants from other parts of empire, eradicating local culture. Southern Caucasus was borderland for Arab caliphates, Ottomans, Persian empires, etc. Northern Caucasus was generally independent until the Russians invasions of 19th century. Lack of a strong state, hence lack of strong ties with outer world, hence local culture / language does not get mixed with others.
2. Safety from migration waves. Take a look at Hun migration routes, Slavs, Germans, Mongols, etc. Caucasus mountains are hard to cross, so migrating people over the years were choosing any other directions. Hence, Caucasus locals are left undisturbed, hence their languages stay intact.

Answer 2

There is also a simple geographic explanation to this issue. Mountains divide people, rivers bring them together. If you look at the most stable boundaries in the world, they are those that are along mountains.

The Caucasuses are, of course, highly mountainous. For protection, for food, and for simple energy conservation, once a culture is established on a mountain, it's hard to move it. And, as different groups establish themselves on different mountains, they tend to differentiate. Simple time encourages mistaken kingdoms to be small and varied - and the Caucasuses, like most mountainous areas (the himalaya, the Appalachian, The Alps) tend to encourage lots of small micro cultures.