This was done by tracing the maternal lineage. The marker are only found in Jews whose mother descends from a woman who descends from a woman…. all the way back to one of the 4.
If a Jewish boy would ever marry a goy, then the marker would not be present. Now social pressures in a small village might prevent such a marriage, but many Jewish men were mobile. They were merchants and tax collectors. It would not be hard for them to marry a goy and then go to another town and live there as man and wife.
So this study is tracking those people who really, really, really wanted to keep the bloodline pure. It is not a question of a maternal lineage but of a MATRIARCHY where the woman's word is law and NOBODY disobeys, nobody. Does this sound Jewish to your? Or does this sound like the satanic descendants of the worshippers of Moloch and the golden calf?
They are not all evil, but it is in this group that you will find the truly evil ones.