We have two sub groups that have developed in the Mid Argyll Kinship Group. The DNA locus 485 has a value of 13 for all the Mac Eáin origin surnames and a value of 16 for the rest of the men in the project. The norm for the R-L21 haplogroup is in fact 15. So, both sub groups within the Mid Argylll Kinship Group, i.e. the R-L21 9919 A-1 group to use geneticist jargon, have a 485 different than the norm. This is a valuable research factor.
This mutation of the Mac Eáin sub group may have happened circa 1450 to 1550. Pure speculation. It may be 'the' marker of families that descend from Donnchaidh Mór Mac Eáin, as his family used the surname McCain beginning in the late 1400s.