Why do some languages (Armenian, Chechen, Korean…) have almost no living relatives, while others (Turkic, Romance) have tons of obvious cousins?
Turkic all clearly sound related. Same with Romance, or Hindi/Urdu. But then languages like Armenian, Korean, Chechen, Lezgin seem to stand almost alone.
• How did Armenian end up with no surviving sister language? Where did the "in-between" relatives go?
• Chechen and Lezgin are technically related
(Northeast Caucasian) but sounds totally different now. Why did the Caucasus end up with something like 40 distinct languages crammed into one small region, instead of one family taking over like happened on the steppe?
• Is Korean actually a full isolate, or does it have real relatives?
• More broadly — how do these languages end up in their current regions? Did speakers migrate into isolated pockets, or did isolation happen after they settled?
Why do some languages spread into big obvious families and others stay alone?
Curious what people who actually study this professionally think.