DNA evidence questioning how many of the O’Mahonys, McCarthys, O’Donovans migrating to West Cork c 1250 AD are of the families.

Recent advances in DNA is calling into question the presumptions of genealogy. In essence families such as the above were displaced by the Normans from South Tipperary and Limerick and migrated to West Cork.
Everybody with the name assumed that they are of the migrating families. Looking at the genetic evidence it appears as if some if not a lot ave marked more associated with the pre existing population in West Cork.

What may have happened is that the migration did take place but perhaps of an elite in the manner of the Celts. The local people where they med to them emulated them taking on their names.