What is the most recent example of a language which has split from another and become non-mutually comprehensible?

Question

I know linguists like to say "no languages are older or younger than other languages" because they all evolved from ancient roots. With exceptions such as Nicaraguan Sign Language.

So let me explain that I'm specifically talking about cases where one settled language splits and one branch gains a degree of non-mutual-comprehensibility with the trunk. I'm interested only in the cases where few linguists would disagree that the result is two languages.

The recent cases I can think of are:

• Yiddish from High German
• Afrikaans from Dutch
• Maltese from Arabic

Without getting too deeply into controversial cases, would one of these or some other I've overlooked be the most recent?

Answer 1

A recent example from Southern Africa:

The Mfecane in South Africa in the early 1800's, caused by Shaka's military campaign, created a whole lot of social upheaval, the repercussions of which were felt as far away as Tanzania.

In the midst of all the attacks and counter-attacks, invasions &c, a powerful group of Sesotho speakers (the Makololo), having adopted many of the techniques used by Shaka, went on the rampage, ended up in Southern Zambia, and subjugated a community of Luyana speakers. The original conqueror died and his daughter took the reins, his daughter gave up the throne to her brother, and her brother was defeated by the Luyana some 30 years after the initial invasion, chasing most of their invaders out of their homeland.

During those 30 years the Makololo had forced the Luyana to speak Sesotho -- a rather distantly related language with clicks, a large number of vowels, a distinction between aspirated and unaspirated consonants, and many other features which made the language difficult for Luyana speakers -- and the result is that the Luyana speakers developed a new language derived almost entirely from Sesotho (essentially, a creole).

That is, we have

• Sesotho > Serotse/Silozi

over a period of a few decades, as recently as 170 years ago.

Answer 2

We do not (I believe) want to get into the tedious discussion of what is a “language” as opposed to a “dialect”. I think most of the instances of what you are asking about involve situations where an already written language is provided, for political reasons, with a new system of writing as a way of distancing itself from what had until then been regarded as a form of the same language. For instance:

Portuguese > Galician

Romanian > Moldovan

Persian > Tajik

and probably many others.

Answer 3

In some ways there are a huge number of dialects which are no longer mutually intelligible. How well would someone with a broad Texan accent understand someone with a broad Scots accent? How well would someone speaking African American Vernacular English understand someone speaking Australian Aboriginal English? But these are usually considered to be all one language because even though the extremes may not understand each other, there is a chain of dialects between them which can all be understood. (And most people can speak at different registers.)

Perhaps an example might be the Melanesian creoles of Tok Pisin, Bislama and Torres Strait Creole. They were developed in Queensland in the 1870s onwards, but the first two were then taken back to PNG and Vanuatu. Some people say that they are still mutually intelligible, but after spending some time with one of them I'm sceptical.