Scientists believe that haplogroup I originated with the Gravettian culture of Paleolithic Europe.

A newly identified subclade, I2b, which has occasionally been mistaken for a variant of haplogroup G

in previous studies, occurs in parts of Northern Ireland and Western Scotland, as well as in the Northern

Germanic parts of Europe.

Like I1, I2b is believed to have originated during the Paleolithic, and to have taken refuge

from the Ice Age in Iberia. Afterwards, it spread into other portions of Europe,

especially The Low Countries, Germany and, possibly, the British Isles.

Many of the Celts who colonized the British Isles from continental Europe may have

belonged to I2b. I2b may even have come to the British Isles far earlier.

The Caledonians, a Pictish tribe that was defeated by Agricola at the battle of

Mons Graupius, were described as Germanic in appearance. Other tribes were

described as dark and Iberian. This anecdotal evidence of an ethnic difference

among the aborigines of Britain does suggest a mixture of haplogroups in their ancestry.

It also supports the coexistence of both "Iberian" R1b and "Germanic" I2b on British

soil prior to either Roman or Anglo-Saxon colonization.

(For more information on the various subclades of haplogroup I, read this excellent study.)