[h=3]Haplogroup I2a1b-L161.1[/h] Commonly known in genetic genealogy circles as "I2-M423-Isles", L161.1 is found at highest frequencies in western Ireland (5-10%) and the Scottish Highlands (1-5%), but is also found at low frequencies (> 1%) throughout Central and Western Europe, from Latvia, Lithuania and Belarus to the British Isles, and from Scandinavia to north-western Spain. It has also been found in Albania, northern Greece, Bulgaria and Romania.
Overall the distribution of I2a-L161.1 is somewhat reminiscent of the extent of Germanic migrations. Its close phylogenetic relation to I2a-L621 branch means that L161.1 was probably absorbed early by the Indo-European migrations too. Its higher concentration in western Poland and northern Germany hint at an absorption by the western sweep of the Corded Ware culture. Around 2400 BCE the Corded Ware culture in Germany, Bohemia and western Poland was overrun by the
Unetice culture, which represents the advance of R1b branch of Proto-Indo-Europeans from Southeast Europe. From then on, I2a-L161.1 would have been able to spread to Western Europe with the Proto-Celts (most probably the
R1b-L21 branch) and to Scandinavia with the Proto-Germanics (chiefly
R1b-S21). That would explain why I2a-L621 seem to correlate with the distribution of R1b-L21 (like in Ireland, Scotland and Brittany) on the one hand, but also with all regions settled by Germanic people.