Haplogroup G men who belong to this group, but but who test negative for all G2a subgroups, are rare in Europe but may comprise a significant group in areas east of Turkey where little DNA testing has been done. P15 was identified at the University of Arizona and had become widely known by 2002. Its chromosome location is listed as 21653414. G2a was discovered in medieval human remains found in a 7th- century CE high-status tomb in Ergolding, Bavaria, Germany. The remains were not tested for G2a subgroups.
There are several SNPs which at this point appear to have the same coverage as P15. They are (with their Y-chromosome locations) U5 (rs2178500), L149 (8486380) and L31 (also called S149) (rs35617575..12538148). If any man with the P15 mutation tested negative (ancestral) for any of these, that finding would be the basis of a new G2a category.