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Archiver > GENEALOGY-DNA > 2003-07 > 1059259445


From: "Dennis Garvey" <>
Subject: [DNA] More about R1b subgroups
Date: Sat, 26 Jul 2003 17:44:08 -0500


There's been some discussion on the list lately about the subgroups inside Y
chromosome haplogroup R1b (for example R1b8 - seen in Basques). I'd like to
spell out a couple of reasons why at this point it's not worth giving much
thought to these subdivisions. But I should also add that a couple of years
from now R1b subgroups may be very interesting in terms of "deep ancestry"
of paternal lines.

Right now more than 80% of European R1bs don't belong to any of the eight
known R1b subgroups. Knowledge of R1b subgroups is still at a very
rudimentary stage - only a few subgroups have been identified. The eight
known R1b subgroups shown on the YCC haplogroup chart do not represent any
major organization among R1bs. They are really just the result of the tiny -
and somewhat skewed - sampling of R1bs in which a hunt for new R1b subgroups
has been done.

The process required to hunt for new biallelic markers is much more
painstaking than that for just genotyping markers that have already been
identified. The massive effort required to search a several thousand base
long stretch of the Y chromsome has limited the search for R1b subgroups to
a surprisingly small sampling of R1bs (first reported in Underhill's
publication in Nature Genetics, vol 26, p. 358, 2000). Those eight R1b
subgroups are based on a search among R1bs of the following nationalities: 2
or 3 Basques, 2 or 3 Italians, a Sardinian, an Australian, a Central Asian
(Uzbek?), two Arabs, and maybe a German. That's not exactly the sampling
that most of us genealogists would have asked for.

Here's the breakdown of the eight R1b subgroups they saw:

R1b1 (M18) - Seen in both R1b Sardinians in study
R1b2 (M37) - Australian (possibly 5% of European R1bs?)
R1b3 (M65) - 5% of Basque R1bs
R1b4 (M73) - 35% of Central Asian R1bs (seen in Uzbek?)
R1b5 (M126) - 3% of European R1bs (probably seen in an Italian)
R1b6 (M153) - 15% of Basque R1bs
R1b7 (M160) - 10% of European R1bs (probably seen in an Italian)
R1b8 (SRY-2627) - 13% of Basque R1bs

So the only reason that there is a Central Asian R1b subgroup among the
eight is that an Uzbek happened to be among the small number of R1bs that
were sequenced. Likewise, the disproportionate number of Basque R1b
subgroups is just a result of the overly large sampling of Basques.

There are only three of the known R1b subgroups that might be of interest to
most genealogists. R1b7 was seen in about 10% of European R1bs. It was
probably first identified in one of the Italians - but may not be limited to
Italians. R1b5 was seen in about 3% of European R1bs - and was also probably
first identified in one of the Italians. R1b2 is a subgroup first identified
in an Australian. If it can be assumed that his paternal line was of
European descent, then about 5% of European R1bs belong to this subgroup.

In the YCC nomenclature, an R1b that doesn't belong to any of the known R1b
subgroups is written as R1b*. More than 80% of the European R1bs are in the
R1b* category (and 65% of the Basque R1bs are also R1b*). So subgroups won't
be of much interest until more of the R1b subgroups are identified. The
knowledge of subgroups of other branches of the Y chromosome tree (for
example YCC J2, I1b, or R1a1) is probably equally "spotty". There's alot of
research that needs to be done yet.

Similar "hunts" for new biallelic Y chromosome markers have also been
conducted by Hammer and by Karafet. The 2001 Hammer study (reported in Mol
Biol Evol, Vol 18, p. 1189, 2001) sequenced several stretches of Y
chromosome in a worldwide selection of 57 men - including 11 Europeans. (The
nationalities of the Europeans were not specified). We can probably assume
that there were six or seven European R1bs among those sequenced in this
study - however no new R1b subgroups were found. The markers discovered in
studies by Hammer usually begin with "P" (for example P25) while those
discovered by Underhill usually begin with "M" - so most of the R1b
subgroups are defined by "M" markers.

The difficulties in sequencing have limited hunts for new biallelic Y
markers to about 50 men in each study. These initial studies sampled men
from around the world - which limited the number of Europeans in each study
to only 8-10. (See Hammer and Zegura, Ann. Rev. Anthrop. vol 31, p 303-321,
2002). A similar hunt for new markers needs to be conducted among just
Europeans (or preferably by European country) to gain a better understanding
of the structure of R1b subgroups. So far, no such study has been published.

Here's the good news: these finer and finer subgroups are defined by
mutations that have happened more and more recently in time. Uptil now
haplogroup classsification has been fairly useless for pinpointing
geographical origins of paternal lines because too much population movement
around Europe has happened since those defining mutations occurred. But some
of the soon-to-be identified subgroups may have originated recently enough
that the descendants won't have moved around much in the intervening time.
So someday R1b subgroups may be able to provide some geographic information
to help out the ranks of us "generic" R1b*s. But we are not there yet.

Dennis Garvey
___________________________________________________________
Y-Chromosome Haplogroup Website

http://freepages.genealogy.rootsweb.com/~dgarvey/DNA/markers.htm
___________________________________________________________

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