I am a participant in the U106 group (R1b1b2a1a) at Familytreedna.com, which has over 800 group participants and continue to grow at a steady pace.
Here is a quote from the group moderator:
"As more and more information becomes available we are seeing the geographic concentration of R-U106 group participant paternal ancestry increasingly centered on north western Europe, and the Netherlands and Belgium in particular; the region historically known as Frisia. Whether or not this represents the origin of the R-U106 founder himself or the most recent common ancestor of the majority of group participants who migrated to Frisia from elsewhere some time in the last few thousand years remains to be determined.""
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