A Question regarding the higher R2 (M124) frequencies in Bangladesh

[R2_M124]

I tested R2 (M124) positive a few months ago, since then I did research about my ancestry & found out that its most commonly found in Bangladesh & India

2 DNA studies both showing that R2 (M124) is a common Y-DNA in Bangladesh although not as common as R1a, whats important about this is that R2 (M124) unlike R1a is found in much lower frequencies elsewhere in the world, making it a marker associated strongly with Bangladesh

The first DNA study:
Haplotype diversity of 17 Y-chromosomal STR loci in the Bangladeshi population
was published on Public Medical journal
Haplotype diversity of 17 Y-chromosomal STR loci i... [Forensic Sci Int Genet. 2010] - PubMed result

15% of Bengali are R2 (M124)
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The Second DNA study:
Genotyping Bengali males from Bangladesh & the West Bengal
was published on The Genetic Atlas
Genotyping Bengali Males - Abhik et al. 2010

12% of Dahaka Bengali are R2 (M124)
14% of Kolkata Bengali are R2 (M124)
40% of Gaibunda Bengali are R2 (M124)
08% of Sylhet Bengali are R2 (M124)


I was wondering if anybody knows the history of Gaibunda?