Which dialect of Common do your PC's speak?

There's an interesting post over at Language Log about linguistic diversity in pre-historic Europe, which could have significant implications for anyone running a game in a world without large, culturally homogenizing nation states.

"The basic fact of pre-state language distribution is that no single language can occupy, for more than a few centuries, an area too large for all its native speakers to communicate with each other regularly. The reasons for that are simple and obvious. All languages change, slowly but steadily, over time. Each change originates in a small part of the speaking population and spreads outward through the speech community. [...] Many changes either spread through the entire community over two or three generations or are suppressed by social “stigmatization”; some are accepted by some parts of the community but not by others, creating “dialect” differences within the broader speech community. But if parts of the speech community cease to communicate altogether, or communicate so rarely that they have no incentive to imitate each others’ speech, changes cannot spread from one to another; different changes will accumulate on either side of the linguistic barrier, and within a thousand years, at most, a single language will have become two or more. [...] Thus in pre-state communities every language spread automatically results in language fragmentation. Of course not all the fragments survive; pre-state language communities sometimes gradually abandon their native language and adopt the language of another community with which they are in intimate contact...."