I was talking about language dispersals today, and so this piece by Nigel Williams in Current Biology is topical: "New language found". The article describes the "discovery" (by linguists) of a language isolate in northeastern India.
Only about 800 elder speakers were found and the language is not written, [Gregory] Anderson says.
Although the Koro speakers live in remote hillsides, it is unclear how the language came about amongst the surrounding 10,000 person Aka tribe.
Well, a history of expansion of other languages at the expense of Koro -- maybe Aka but not primarily so in recent years considering the much more massive growth of languages now spoken by millions in India.