I have traced my family back to 1547, about the middle of the "Little Ice Age". There was a time when only 2 of 19 children lived long enough to carry on the family name. The family was living in the "Swabian Alb" part of Germany, and were farily well off (as I understand it). I could understand how an entire culture COULD disappear within a few generations. That could be especially true if they were prevented somehow from leaving a specific area.
I managed to trace my Family surname back to March 10, 1340 at what is the start of the Little Ice Age. The Pyrenees Area of SW France made out quite well during the Little Ice Age. The old Family Maison is still lived in by the Family.