McCool Y-DNA Test Results

Unlike autosomal DNA tests (such as AncestryDNA), Y-DNA tests provide accurate information that stretches back thousands of years. Y-DNA tests prove absolutely that two men are (or are not) related on their direct paternal line (father to father's father to his father...and finally to a shared male ancestor) at some point in history. Ideally, we hope to find multiple close same-surname matches, who've all tested a large number of markers (67 markers, or even better 111+), and who all have strong paper trails showing their likely relationship.

Because Y-DNA testing is still somewhat uncommon (even in America), that rarely happens on its own. Researchers like me try to identify the gaps in a specific paternal line (such as McCool), and then work to discover descendants who are distant cousins to take a Y-DNA test to fill in the missing knowledge.

How unrelated McCool lines form

Until the late middle ages, most families in Ireland and Scotland followed a patronomic naming practice. Patronyms changed with every successive generation (for example, the patronyms of a grandson, father, and grandfather may be John Donaldson, son of Donald Robertson, son of Robert Williamson). The Welsh version of son was "ap" and the Gaelic version was "Mac" (sometimes shortened to "Mc." Patronym naming practices ended in the Scottish Lowlands in the 1500s, but sometimes stayed active in the Highlands well into the 1700s.

No one knows the origin of the surname McCool. If you search the web, a number of theories are proposed. It's possible that one of the theories might explain the surname origin for one McCool line, while another theory might explain the origin of an unrelated McCool line. Perhaps none of the theories are correct, and McCool is just a derivative spelling of MacColl, son of Coll - and that several sons of different Colls adopted the surname in the 1500s.

Thanks to Y-DNA testing, we know there at least five separate McCool lines in the world that are unrelated (at least on their direct paternal lines). It doesn't surprise us when we learn that two men named Smith aren't related; it shouldn't surprise us in the case of McCool either. Some of the McCool lines were probably independently established when use of surnames were first adopted. Other McCool lines may be because a child was raised in a McCool household and took that surname, but his biological father wasn't a McCool. This could be due to an out-of-wedlock birth, or because the child was adopted after the death of one or both parents.

My speculative theory

Unfortunately, we don't have nearly enough McCool Y-DNA tests to draw informed conclusions. My current, but wildly speculative, theory is that three or so unrelated families independently adopted the surname that became McCool over a period of 100-300 years in Scotland and Ireland. Other McCool lines may have formed when an unrelated (on the paternal line) child was adopted into a McCool family. That last possibility goes both ways, of course. Two of our known Y-DNA proven Toberhead McCool descendants carry non-McCool surnames.

In the fall of 2018, I became the volunteer McCool surname project administrator (within the COLE surname project) at Family Tree DNA. There are very strict rules about what I can disclose as the project administrator. The information on the Toberhead lines was provided outside of the project, prior to when I joined it. I've decided that I am behaving in the spirit of the rules by providing their line, while hiding the name of the Toberhead member tested as well as his father (all of which I learned outside of the project).

I've been able to locate thirteen McCool-surname Y-DNA tests on FamilyTreeDNA (as of February 2019). Five of the tests definitely match to our family, one definitely does not, and the other two have the potential to unlock some secrets as to how our McCool lines may or may not be related. I've submitted requests to the tested McCools asking them to share their genealogy trees so we can learn more.

Who Should Test?

More tests are always better than fewer tests. Although Y-DNA mutates at a moderate pace and can vary from father to son and even brother to brother, most people only test one male per extended family (out to second cousins or so.) Most of the time, people that closely related will have identical (or extremely similar) results. Please test at the Y-37 level or higher; Y-67 or Y-111 are better. You also have the option to upgrade in the future.

Once you've tested, please join the following FTDNA groups:

  • All McCool testers should join the Cole surname project.
  • Anyone with a predicted haplogroup of R-M269 should join the R1b Project.
  • It looks like our Toberhead McCool lines are members of R1b subclade L-513. Join the R-L513 Project for great advice on any additional testing needed.

Questions? Send me an email at .

Known McCool Y-DNA Test Results

***This section is from 2017 and needs to be updated with 2019 information.

Based on these tests, we know that our McCool ancestors are members of the very broad R-M269 subclade of the R1b Y-chromosome haplogroup - the most common Western European haplogroup. About 82% of the citizens of Ireland and 70% of citizens of Scotland are R-M269 members (although my Ireland-surname line descends from a much rarer R-1a haplogroup in Ireland/Scotland.)

Here are the 8 Y-DNA tests that I've found. Click on the image if you want to open it in a new browser tab - and click again if needed to zoom to a readable level:

Toberhead McCool Lines

I've been able to match five of these tests to descendants of our Toberhead McCool family. Note that generations 7 to 9 are not included, and that no personal information is given after generation 6. There is some disagreement as to the exact line of descent from John McCoole Sr to both Benjamin McCool and Archibald McCool, but the matching Y-DNA tests support that he is the common ancestor for all of the men tested.

Click on the image to open it in a new browser tab for somewhat easier reading:


Are we related?

Here are the GEDmatch Kit #s for my father and mother:

GI: A909282
CL: A216073

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