Haplogroup I1b (Y-DNA)

In human genetics, Haplogroup I1b (S31) is a Y-chromosome haplogroup. Its subclade I1b1* is typical of South Slavs, especially Croats and Bosniaks. Another subclade, I1b1b (formerly I1b2), is strongly associated with indigenous Sardinians, but it is also found at low to moderate frequency among populations of the Basque Country, Iberia in general, France, mainland Italy, the British Isles, and Sweden. Contrasting with the tendentially southeastern distribution of I1b1* and southwestern distribution of I1b1b, the subclade I1b2 is most commonly found among populations of Northwest Europe, especially Denmark, Germany, the Netherlands, and the British Isles.

Subclades

 * I1b (S31)
 * I1b*
 * I1b1 (P37.2)
 * I1b1*
 * I1b1a (M26) formerly I1b1
 * I1b1a1 (M161) formerly I1b2a
 * I1b1b (P41.2 (M359.2)) formerly I1b2
 * I1b1b*
 * I1b2 (S23, S30, S32, S33)
 * I1b2*
 * I1b2a (M223, S24) formerly I1c or I2
 * I1b2a*
 * I1b2a1 (M284) formerly I1c1 or I2a
 * I1b2a2 (M379)
 * I1b2a3 (P78)
 * I1b2a4 (P95)

I1b1*
Haplogroup I1b1* (P37.2) accounts for most of the Haplogroup I component in the Y-chromosome diversity of Eastern European populations, reaching its peak in the Western Balkans, most notably in Dalmatia and Bosnia-Herzegovina (40 - 50%).

The high frequency and diversity of Haplogroup I1b1* among populations of the Western Balkans lends support to the hypothesis that the Adriatic region of modern-day Croatia served as a refuge for populations bearing Haplogroup I1b1* during the last glacial maximum.

I1b1b
Haplogroup I1b1b (P41.2 (M359) accounts for more than 40% of all patrilines among the Sardinians.

A distinct Western European Paleolithic population that bore Haplogroup I1b1b (M26) must have existed somewhere west of the Apennines in eastern Iberia, southern France, or western Italy, from which it succeeded in the first substantial colonization of the island of Sardinia approximately 9,000 years ago. Despite the fact that the predominantly Sardinian Haplogroup I1b1b-P41.2=M359 is derived from the predominantly Balkan Haplogroup I1b1*-P37.2, the derived Haplogroup I1b1b is practically absent east of France and Italy, while it is found at low but significant frequencies outside of Sardinia in the Balearic Islands, Castile, the Basque Country, the Pyrenees, southern and western France, and parts of the Maghreb, Great Britain, and Ireland. Thus, Haplogroup I1b1b appears to be strongly associated with Southwest Europeans of Paleolithic ancestry, and its carriers bear only a distant relictual relationship to the I1b1*-bearing populations of the Balkans. It is also interesting that, although the distributions of Haplogroup I1b1b and the predominantly Scandinavian Haplogroup I1a overlap in parts of western France and the British Isles, and both haplogroups appear to have a very long history in Southwest Europe (and particularly France), the populations bearing these two haplogroups appear to have differentiated at a very early date and have not extensively mixed since that time. Haplogroup I1b1b appears to be the only subclade of Haplogroup I found among the Basques, although subclades of Haplogroup R1b comprise the vast majority of that people's Y-chromosome diversity. It is notable that Haplogroup I1b1b appears to be found at somewhat higher frequencies among the general populations of Castile in Spain and Béarn in France than among the population of ethnic Basques. Lastly, the unique phylogeography of this clade has caused some scientists (Gatto, Michael) to posit that the clade should be associated with the spread of Chalcolithic Megalith culture in Western Europe. The M26 mutation is found in native males inhabiting every geographic region where megaliths may be found, including such far-flung and culturally disconnected regions like the Canary Islands, the Balearic Isles, Corsica, Ireland, and Sweden. As of 2007, no specific study has confirmed this hypothesis, although the data in several previous studies (Rootsi, et al., Flores, et al., etc.) support this hypothesis.

I1b2
The distribution of Haplogroup I1b2 (S23, S30, S32, S33) is closely correlated to that of Haplogroup I1a except in Fennoscandia, which suggests that it was probably harbored by at least one of the Paleolithic refuge populations that also harbored Haplogroup I1a; the lack of correlation between the distributions of I1a and I1b2 in Fennoscandia may be a result of Haplogroup I1b2's being more strongly affected in the earliest settlement of this region by founder effects and genetic drift due to its rarity, as Haplogroup I1b2 comprises less than 10% of the total Y-chromosome diversity of all populations outside of Lower Saxony. Haplogroup I1b2 has been found in over 4% of the population only in Germany, the Netherlands, Belgium, Denmark, England (not including Wales or Cornwall), Scotland, and the southern tips of Sweden and Norway in Northwest Europe; the provinces of Normandy, Maine, Anjou, and Perche in northwestern France; the province of Provence in southeastern France; the regions of Tuscany, Umbria, and Latium in Italy; and Moldavia and the area around Russia's Ryazan Oblast and Republic of Mordovia in Eastern Europe. One subclade of Haplogroup I1b2, namely I1b2a1 (M284), has been found almost exclusively among the population of Great Britain, which has been taken to suggest that the clade may have a very long history in that island. It is notable, however, that the distributions of Haplogroup I1a and Haplogroup I1b2 seem to correlate fairly well with the extent of historical influence of Germanic peoples, although the punctual presence of both haplogroups at a low frequency in the area of the historical regions of Bithynia and Galatia in Turkey rather suggests a connection with the ancient Gauls of Thrace, several tribes of which are recorded to have immigrated to those parts of Anatolia at the invitation of Nicomedes I of Bithynia.

Haplogroup I1b2 also occurs among approximately 1% of Sardinians.