Why did the Ashkenazi population have a bottleneck 600-800 years ago?
This article from the Times of Israel: https://www.timesofisrael.com/ashkenazi-jews-descend-from-350-people-study-finds/
says that 600-800 years ago, the Ashkenazi population had a 350-person bottleneck which seems dramatic.
What happened? Is there a known event?