This is a Surname DNA Project for variants of Cleary, Clery, Clary, Clark, related to the old Irish surname Ó Cléirigh. The Project is predominantly a Y-DNA project, as the purpose is to investigate the spread of the surname across medieval Ireland and beyond, but it is open to anyone who has taken a test with FTDNA (Y, Family Finder or mtDNA) who has the one of the related surnames, or is recently descended from an ancestor with one of the surnames and is interested in researching its history and distribution.

If your surname is Clark or a variant and you believe it is of Irish origin connected to the Ó Cléirigh names you are welcome to join the Project. If your surname is Clark or variant and it is not thought to be of Irish origin, you may be interested instead in the Clark(e) Surname Project at https://www.familytreedna.com/groups/clark.

As a surname, Ó Cléirigh is thought to be one of the oldest in Europe, and some argue it is the oldest. It is linked to Cleireach Mac Ceadadhach, a 9th century chief, whose descendants adopted Ó Cléirigh as their surname. The name can also be read as meaning ‘clerk’ or ‘cleric’. The DNA project has shown that there are several lineages of Cleary-type names (including Cleary, Clery, Clary, often anglicised as Clark) which are not related to each other in historical time, and sometimes mixing different variants. The name is likely to have been adopted more than once in different parts of Ireland and in different eras.

If you have taken a DNA test or uploaded your results to FTDNA you are able to join this project, view the current results and to post in the Activity Feed. Please keep all posts related to the topic of the history and development of the surname, or they may be deleted. It is very useful to post your genealogical information in the Feed for other members to compare theirs with. If you have not taken a DNA test but would like to participate in the Project, consider taking either a Y-37 test or the Family Finder. Best results come from taking a Y test – if you do not have a Y chromosome of your own you can consider recruiting a suitable relative who could take the test for you. Contact the Admins for advice about this.