tgpedersen wrote:
> I suspect you have peeked in the folder of maps of Oppenheimer's gene
> variants, and found the I (Ivan) and I1c (Ingert) maps, with their
> distribution in Croatia, North of the Black Sea, and North
> Germany/Netherlands/England/Scandinavia and expected me to ask
> annoying questions why this was so, so you initiated a counter attack,
> before I could ask the question, which I am doing now: What caused
> this odd distribution?
>
There are many possible explanations but I will present a scenario that
in my opinion is the most likely.
According to this scenario, the haplogroup I was introduced to Europe by
the first wave of modern humans (Cro-Magnons) - circa 40,000 years ago.
This is the only Y chromosome haplogroup that is almost completely
absent outside Europe (if we don't count the relatively recent
migrations of Europeans to America and Australia) and its sister
haplogroup J is a major haplogroup in the Middle Eeast and Caucasus.
There was a relatively early split within the haplogroup I, which
corresponds to the two subclades Ia and Ib that are recorded today (for
the most recent classification of the subclades see
http://www.isogg.org/tree/ISOGG_HapgrpI08.html). All males from the Ia
subclade (the <Scandinavian> one) share 15 newly acquired known
polymorphisms (as opposed to only 6 known I-specific polymorphisms that
are shared by all males from this haplogroup), suggesting that this
subclade was separated from the remaining haplogroup I subclades a long
time ago (and its homogeneity may indicate that all Ia males descend
from a relatively small population that was able to survive and then
expand in more recent times). By contrast, the Ib subclade splitted very
soon (with both branches surviving till today) into I2a an I2b. Then the
I2a subcalde splitted again - the I2a1 subclade is very frequent in
Sardinia and occasionally seen in the Iberian peninsula, whereas the
I2a2 subclade survived mostly in the Balkan peninsula, being very
frequent in Bosnia and Croatia (but relatively frequent also in other
Balkan countries, Moldavia, and even Ukraine). The second branch of I2
(the I2b subclade), represented mostly by I2b1 (formerly known as I1c),
is most frequently seen in the Netherlands and Germany (about 10% of all
Y chromosomes), but is also found in France and Slovenia.
So here are some details of my scenario:
The first modern humans came to Europe through the Bosphorus and Balkans
or, alternatively, through the Caucasus and the plains of the southern
Ukraine. Soon after their arrival to Europe (or even during this
migration) the major split of this population took place. One branch
(corresponding to the I1 subclade) migrated to the North-East
(Kostienki-Sungir culture) and the other branch (I2) was responsible for
the expansion of the Aurignacian culture in central and western parts of
Europe. The I2 branch (with its many subclades) was also most likely
responsible for the later development of the Gravettian, Solutrean and
Magdalenian cultures. Frequent population movements, forced by multiple
climate changes, make it very hard (if not impossible) to ascribe a
specific genetic marker to a given archeological culture (which per se
would be a crime in the eyes of most specialists - but we do it only for
fun, don't we?). I would, however, guess that the I2a males participated
in the spreading of the Epigravettian cultures from the Central Europe
to the southern parts of the continent. It seems also likely that the
I2b males contributed to the (much later) expansion of the Magdalenian
culture (especially northward).
Let's focus for a moment on the I1 (Scandinavian) branch of this
haplogroup. I ascribed them to the Upper Paleolithic Kostienki-Sungir
culture. Many cultures that developed in the northern part of Europe are
untracable today because of the glaciation that covered this part of the
continent. Thus, finding the traces of cultures that could correspond to
the continous development of a population (or populations) representing
the I1 branch seems impossible, although we know that the
Kostienki-Sungir culture advanced further north, reaching as far as the
Petchora basin (Byzovaya). My scenario is additionally based on the
assumption/hypothesis (questioned by some specialists) that there is no
continuity (or clear "genetic" relationship) between the late upper
paleolithic post-Magdalenian cultures in northern Europe (Ahrensburg,
Hamburg) and the more eastern epipaleolithic/mesolitic Bromme-Lyngby
culture. On the other hand, there seem to be important similarities
between the Brommme-Lyngby and Kostienki-derived cultures of reindeer
hunters. Thus, the expansion of th mesolithic population of Scandinavia
(and generally north-eastern Europe) would in my opinion correspond to
the expansion of the I1 subclade. Consequently, the I1 subclade would
also have been present in the later Maglemosian, Kongemose, Ertbolle nad
TRB cultures. To some extent, the incorporation of the
Ahrensburg-derived populations (I1b in my scenario) could also have
taken place, so when the Indo-Europeans (haplogroup R in my scenario,
more specifically subclade R1b in this case) arrived (Corded-Ware,
pre-Corded-Ware, Globular-Amphora, or Baden/post-Baden) they intermixed
together, which lead to the formation of the Pra-Germanic population,
where R1b, I1 and (to the lesser extent) I2a were the three dominant
haplogroups. Another group of I1 people (males), located in the
north-east, mixed with the incomming Finno-Ugrians (haplogroup N,
subclade N3).
As for the Slavs, they arrived much later, bringing the R1a subclade of
haplogroup R. Since the R1a subclade is common in almost all
Satem-speaking populations (including Iranians) and is also present (but
not very frequent) in Scandinavia and Britain (sometimes even regarded
as a marker of Viking ancestry) this could make a new interesting
starting point to your speculations about the possible Iranian-Germanic
relations.
I would like to bring your attention to the fact that the haplogroup I
survived mostly in regions that were less accessible for the invaders
(Sardinia, Corsica and mountainous regions of former Yugoslavia - where
Tito resisted Germans for years) or in populations that are suspected of
having assimilited the local people, as would be the case with the
non-IE substrate in Germanic-speaking populations. One may wonder, why
the haplogroup I is not frequent among Basques, but this may be related
to the matrilocal marriage tradition, which would explain the lack of
correlation between the male (Y chromosomal) genetic markers and the
language.
All above is just a hypothesis (a rather amateur one), and I must warn
you that many other theories, linking the Y chromosome markers with the
archeology and linguistics, may much more deserve your attention.
Regards,
Michal