Funny the possibility wasn't offered that the climate changed suddenly, which caused a social collapse. I mean, it's nothing that hasn't happened in other places, such as Europe at the beginning of the Little Ice Age. :')
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.