> And local dialects are anything but unusual, they appear even in not so isolated regions of small european countries. Which is a lot less likely place for a local dialect to survive than northern Swedish forest is.
I was always amazed by the linguistic diversity in Italy, much of which is anything but isolated. Even in the plains of the Veneto, you can ride a bike far enough for the locals to tell that you're from a different area (without even looking at what's written on your jersey!).
I live in London, and you can tell South/East/North/West London apart with relatively little practice. On top of that there are several distinct dialects in the surrounding areas (1-2 hours travel out of inner London), as well as a few different sociolects (dialects spoken by distinct socio-economic groups more than separated by area).
In Norway, a 2h ferryboat trip can take you from a city where people speak fairly mainstream Norwegian to an island where the locals cannot be understood by most Norwegians (unless the locals make an effort and speak mainstream).
I was always amazed by the linguistic diversity in Italy, much of which is anything but isolated. Even in the plains of the Veneto, you can ride a bike far enough for the locals to tell that you're from a different area (without even looking at what's written on your jersey!).