Celtic, Italic and Germanic people are all descended from the same R1b1b2 stock. They split north of the Alps.

The Italic branch went south and mixed with the Terramare people who were I2a, G2a and E-V13. Northern Italians have more Indo-European Celto-Italic blood, while southern Italian have more indigenous blood (the highest being Sardinia, then Basilicata).

The Germanic branch moved north and mixed with the indigenous I1 and I2b people, who had already mixed with R1a migrants from the Corded Ware (Battle Axe) culture. The new hybrid Germanic people retained the highest percentage of aboriginal haplogroup I.

Celtic people split in several groups : the Brythonic went to Britain and Ireland, the Gaulish to France, the Iberian to Spain and Portugal, and the Alpine remained around Austria, Switzerland, southern Germany, Eastern France and Belgium. The Iberian and Gaulish groups mixed with I2b, I2a and E people, the Alpine with I2b and E, and the Brythonic just with I2b people.

It is likely that the language of the aboriginal Europeans influenced the various Celtic, Italic and Germanic dialects. Germanic languages diverted the most from the original European R1b language because it assimilated a very large part of aborigines.