A Wee Bit Irish

Top o' the Morning to Ya!

I recently had quite a surprise—I discovered that, for the first time in my life, I’m now a wee bit Irish! Years ago, I submitted my DNA to Ancestry, but it wasn’t until their most recent update that I suddenly gained 2% Irish ancestry. How is that possible? How can Ancestry (or other DNA testing companies like 23andMe, MyHeritage, or FamilyTreeDNA) tell me one thing, only to change my results later? What causes these shifts in ethnicity estimates?

It turns out that shifting results in DNA ethnicity estimates are a common occurrence in genetic genealogy for a number of reasons:

DNA Ethnicity Estimates Are Just That—Estimates

When companies like AncestryDNA, 23andMe, MyHeritage, or FamilyTreeDNA analyze your DNA, they are not reading a "nationality label" in your genes. Instead, they compare your genetic markers to reference populations—groups of people whose ancestry is well-documented and who have lived in a particular region for generations. Your DNA is matched against these groups, and an algorithm determines which population(s) your genetic signature most closely resembles. As more people from various regions test their DNA, companies refine their datasets and make ethnicity estimates more precise. This means that as the reference panel grows, your estimated ancestry may change.

For example, let’s say your ancestors were from an area where Irish, Scottish, and English populations historically mixed. Years ago, the available reference samples may not have been detailed enough to distinguish between them, so your DNA may have been classified as only "British." With more refined data, Ancestry might now recognize small genetic markers linking you specifically to Ireland.

DNA testing companies regularly update their analysis methods. With each update, they adjust the way they group genetic markers, sometimes shifting ancestry estimates in the process. AncestryDNA, for example, has released multiple updates in the past decade, each time refining its ethnicity estimates based on improved research and larger sample sizes.

Keep in mind also that many populations share genetic similarities. The British Isles, for example, had frequent migrations between Ireland, Scotland, England, and Wales, making it hard to distinguish ancestry precisely. But, if a company refines its ability to separate Irish from Scottish DNA, for instance, your estimate may shift.

 

Just a Wee Bit of Caution

As a general rule, ethnicity estimates under 5% should be interpreted with caution. These small percentages often reflect the fine-tuning of data rather than a definitive ancestral connection. While it's possible I have a distant Irish ancestor, it’s also possible that this is a result of slight shifts in Ancestry's algorithm rather than a meaningful genealogical connection.

Ethnicity estimates are fun and sometimes revealing, but they are not as precise as traditional genealogical records. They can change over time as companies refine their research, so it’s always best to use them alongside documented family history, historical records, and genetic matches to get the clearest picture of your ancestry.