My comment about Euro-centrism was pointed to this.
Everybody knows how any region in the Italian Peninsula, in the HRE or in Iberia used to have its own language, to a point where nobody would consider arguing that they are actually dialects of a shared languages.
This is not even remotely what the above is saying. It's not a matter of Italian/HRE/Iberia having their own languages. It's a matter of them all being one giant language, or else every insignificant valley having their own totally distinct language, depending on how you want to define the language. It's only Eurocentric inasmuch as I specialize in Indo-European historical linguistics, and Germanics in particular, so that's generally what I'm going to pull from. But the Linguistic continuum isn't a quirk of the European system. It's how languages work. The non-continuum system we have today is a quirk of 20th century developments. Go to India, Rural China, Papua New Guinea, or Southern Africa and it is the reality you'd find there today. I mean, hell, look at a linguistic map of Papua New Guinea today. It's a mess! And it's not a mess because of anything necessarily unique about New Guinean demography or even necessarily geography. That's just what a linguistic reality looks like when you don't get: a) a centuries-long writerly tradition or a strong nationalistic state to rigidly enforce a singular linguistic standard; and plus you
do get b) an international academic community with the interest and funding to actually go down and document the incredible linguistic diversity still present on the island. New Guinea today is what Europe, Mesopotamia, Mesoamerica - what
the entire world looked like linguistically in the pre-modern world.
There is another issue with that paradigm, which was not mentioned enough here -
It is not a perfect geographical spread, simply because human culture did not spread in a perfect geographical way.
While there can be a clear chain of minimal linguistic difference between several Romance dialects from one region to anther across large distances, somewhere in the middle of this chain could be a totally different region who speaks some form of a Germanic language, as a result of centuries of historical political boundaries. It is not simply a matter of radius.
Outsider ethnic groups like Magyars could be quite different from any of their clear Indo-European neighbours. Being geographical (or even religiously - another thing to consider) close doesn't make them sound as similar to Croatians as Bosnians do. A similar thing is with Romanians.
Another kind of incidents is the common case where one territorial far edge of a macro-culture / language family meets the far edge of another. Each of them is much more similar to the languages spoken by the inhabitants of its "historical homeland" than to that other one who borders them.
Back to the Persian discussion - the geographical extent of the empire is not the only thing that matters.
The variety of language families (in a certain upper level which couldn't be debated) can really harm the Peasant/Villager measurement. Possibly one could go 400kms eastwards to find himself not able to communicate (in a distinct culture to his own), while the other could go thrice that way to north-west and get along fine. It is a matter of cultural (or ethnic) presence.
You still aren't entirely understanding what I'm talking about here. Language families aren't absolute or really at all objective. They are classification systems we have developed to describe
languages that we have access to today. Yes the Magyar that we have today - the one descended from a nobility with a written tradition and standard is self-evidently a Finno-Ugric language, and that relationship makes it appear a somewhat isolate because the only languages that exist today around them are Slavic and Germanic languages, but you're commenting on things after centuries of coagulation and language death. Again, if you were to travel down the Danube in the 15th century you wouldn't find such absolute delineations. You'd see a spectrum that flows naturally - imperceptibly even, at the micro-scale - from various Germanic/Alemmanic dialects, to Slavic/Czech dialects, to Hungarian, to Romanian and who knows what else. You the 15th century linguist would have to come up with a completely different classification system to describe what you are hearing.
Our language families appear neat today because it's arranged to fit and describe our modern reality. Those delineations and classifications would be
totally different if we were operating with a) the ability to collect more data than just what's here now and whatever random historical documentary evidence we're lucky enough to chance upon (thank god for the Romans or we'd know fudge-all about Germanics pre-800) and b) the academic funding/manpower and interest to go document it. We'd probably be looking at dozens more sub-branches and perhaps even a rather marked re-evaluation of the Finno-Ugric and Indo-European divide. To return again to Papua New Guinea, linguists have documented almost as many
language families on the island as they have in the rest of the world combined. Again, this isn't because of anything necessarily unique about that island in particular, it's just because we finally have the resources, technology, and knowhow to actually go in an document non-written languages, and it happens to be one of the very few places left in the world that hasn't seen its linguistic makeup subsumed wholesale to a larger written/broadcast/colonial monoglot.
It's also important to remember that demographics != language. Just because a group of people all describe themselves as Persian, doesn't mean they all speak a Persian language or dialect, nor just because a group of people all speak a Persian language or dialect doesn't mean they all identify as "Persian" or are even aware of some larger interconnected Persian linguistic identity. This goes back to what I was saying above. This is a way of thinking that is common today, because it's generally how language works in our modern, nationally-delineated world. People in France speak French; people in Spain speak Spanish; people in Germany speak German - even beyond the obvious ones: people in India speak Hindi, people in Iran speak Farsi, people in Saudi Arabia speak Arabic. Because of this world organization, it's very easy for us to extrapolate backwards - people in Rome spoke Latin; people in Greece spoke Greek; people in Bavaria spoke Bavarian - and sure that works to some extent when you limit yourself to talking about literate elite males, but it's fallacious as a historian to limit yourself to such a narrow human existence, and it doesn't follow from what evidence we do have for linguistic diversity in non-literate societies.