Haplogroup R1b (R-M343) is the most frequently occurring Y-chromosome haplogroup in Western Europe and the most common haplogroup in the genetic genealogy databases.R1b1a2 (R-M269) is the dominant branch of R1b in Western Europe.When you take a standard Y-chromosome DNA test with a company such as Family Tree DNA you will be given a base haplogroup assignment such as R1b1a2 (R-M269).aplogroup R1b (R-M343) is the most frequently occurring Y-chromosome haplogroup in Western Europe and the most common haplogroup in the genetic genealogy databases.