I’ve known several Jews from Iran. One of them claimed ancestry from the Shushan Jews at the time of Queen Esther, about 2500 years ago. I have no reason to doubt him.
I read an article about how the Jewish people were sticklers for their lineage and one of the reasons they could trace Jesus’ heritage back to David. I was under the impression that the practice waned but it makes sense that maybe not all the Jewish sects stopped.