The Heyer study of 1997 recorded a mutation rate of zero for DYS390 and DYS393.

Although the DYS390 marker has not exhibited a mutation rate as consistently low as

DYS393 in other studies, the results of the Heyer study suggest that it is a relatively

stable marker. As such, particular values of DYS390 may be acquired less often by

random mutation, and therefore may be more likely to reflect a shared ancestry among

the haplotypes that exhibit them.

A person of British descent who exhibits any of the DYS390=25 haplotypes below

most likely inherited it from the Paleolithic Iberians who first colonized Britain, or

from Celtic speakers of equally Paleolithic origin who migrated to Britain from Central

Europe about 500 B.C.E.

Alternate origins could include the Normans (or, more properly, their Breton allies),

the Flemish, the Anglo-Saxons, or even Romans of Iberian or Italic extraction,

all of whom occupied areas with a history of Celtic settlement.

Although a "Celtic" ancestry is often casually assigned to anyone from the British

Isles who is R1b, here is a case where that assignment is entirely justified.

Unlike R1b haplotypes where the DYS393 marker value is 12, these haplotypes are not

common in Western Asia and Eastern Europe.

Unlike R1b haplotypes where the DYS390 marker value is 23, these haplotypes do not

exhibit their highest frequencies in The Netherlands, Scandinavia and Northern Germany.

R1b haplotypes with a DYS390 marker value of 25 occur overwhelmingly in Iberia,

and in other classic areas of Celtic settlement, which include the upper Rhine, Western

Switzerland, Northern Italy and the British Isles.