[3] In addition, living examples of the precursor Haplogroup IJ* have been found only in Iran, among the Mazandarani and ethnic Persians from Fars.

Rootsi and colleagues in 2004 also note two other dates for a clade, age of STR variation, and time since population divergence.

This common ancestry suggests that the subclades of IJ entered the Balkans from Anatolia or the Caucasus, some time before the Last Glacial Maximum.

A natural geographical corridor like the Balkans is likely to have been used later by members of other subclades of IJ, as well as other haplogroups, including those associated with Early European Farmers.

[86] Up-to-date phylogenetic trees listing all currently known subclades of I can be found at Y-Full and FamilyTreeDNA Note that the naming of some of the subgroups has changed, as new markers have been identified, and the sequence of mutations has become clearer.

Several I* individuals, who do not fall into any known subclades, have been found among the Lak people of Dagestan, at a rate of (3/21),[89] as well as Turkey (8/741), Adygea in the Caucasus (2/138) and Iraq (1/176), even though I-M170 occurs at only very low frequencies among modern populations of these regions as a whole.

[90] (Neither study from which the above figures were drawn excluded the present I2-M438 clade as a whole, but only certain subclades, so these presumed cases I* may possibly belong to I2.)

[93][94] Haplogroup I2-M438, previously I1b, may have originated in southern Europe – it is now found at its highest frequencies in the western Balkans and Sardinia – some 15,000–17,000 years ago and developed into three main subgroups : I2-M438*, I2a-L460, I2b-L415 and I2c-L596.

Haplogroup I2a1a-M26 is practically absent east of France and Italy,[95] while it is found at low but significant frequencies outside of Sardinia in the Balearic Islands, Castile-León, the Basque Country, the Pyrenees, southern and western France, and parts of the Maghreb in North Africa, Great Britain, and Ireland.

[95] The distribution of I2a1a-M26 also mirrors that of the Atlantic Bronze Age cultures, which indicates a potential spread via the obsidian trade or a regular maritime exchange of some of metallurgical products.

Haplogroup I2a2-M436 has been found in over 4% of the population only in Germany, the Netherlands, Belgium, Denmark, England (not including 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 I2a2-M436, namely I2a2a1a1-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.

This suggestion is supported by recent genetic studies regarding Y-DNA Haplogroup I2b2-L38 have concluded that there was some Late Iron Age migration of Celtic La Tène people, through Belgium, to the British Isles including north-east Ireland.

[99] The technical details of U179 are: This haplogroup reaches its maximum frequency in the Western Balkans (with the highest concentration of I2 in present-day Herzegovina).

[101] The study featured the measured average heights of young German, Swedish, Dutch, Danish, Serbian and Bosnian men.