Claire Bradley, a Dublin-based genealogist, explores the role of DNA tests in family history research, offering expert insights and practical guidance. Learn about the technical and genealogical dimensions of using these tests to trace ancestral lineage and bridge the present to the past.
Genealogical DNA testing
As a professional genealogist, I find that people are increasingly coming to me with questions that could potentially be answered by a DNA-based genetic test. The main type of genealogical DNA test on the market is an autosomal test, which can be bought from Ancestry, 23andMe, MyHeritage and FamilyTreeDNA, as well as other companies.
Once you order from one of these genealogy companies, you’ll usually receive your DNA kit in the post within a few days. The tests can be performed in the comfort of your own home. Some tests require a saliva sample, while others use a cheek swab. After you return your sample by post, it will be processed in the lab and a few weeks later, you’ll receive your results via email.
These home kits are typically priced at around €100, but there are often special offers during holiday seasons like Christmas, St Patrick’s Day, Mother’s Day and Father’s Day, making them a popular choice for gifts. In fact, there are some good offers to be had right now and you can probably save about a third on the price.
Why take a DNA test?
There are many reasons why someone would choose to take a genealogical DNA test but, in my experience, there are four main reasons:
- To trace an unknown recent ancestor (for example, your parents or grandparents).
- To confirm the findings of your traditional genealogical research.
- To find emigrant branches of your family tree.
- To investigate your genetic ethnic heritage.
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How autosomal tests work
First, a little bit of science. Each person gets exactly 50% of their DNA from their mother and 50% from their father. Autosomal DNA tests look at autosomal chromosomes (chromosome pairs 1–22), which are inherited from both parents and all recent ancestors.
The test finds genetic matches with cousins on both sides of your family out to about sixth cousins (with whom you share a set of five times great-grandparents – you have 128 of them!). These genetic matches are measured in centimorgans (cM), and the main thing to remember is that the higher the cM number, the closer the familial relationship to your match.
Unfortunately, you can’t tell initially which side of your family tree the match comes from. However, through a combination of communicating with your match, sharing family trees and searching traditional genealogical records – like civil records, parish records and census returns – you can often figure it out.
Ethical implications in genealogical DNA testing
Of course, there are some ethical considerations when taking a DNA test. You should always understand what you’re agreeing to by reading the terms and conditions. Your DNA will be stored in a genetic genealogy database and your matches can connect with you within this database. In some countries, but not in Ireland, law enforcement has made inappropriate use of such databases to solve cold case crimes.
For instance, the Golden State Killer, who terrorized California in the 1970s, was caught after his DNA sample, found at a crime scene, was uploaded to select genealogy databases, enabling the building of connecting family trees via his DNA matches. The team of six, led by Barbara Rae-Venter, managed to identify the serial killer as Joseph DeAngelo in just 63 days after eluding authorities for 44 years. (Rae-Venter’s book, I Know Who You Are, is a fascinating read!) DeAngelo was ultimately tried and convicted and is now in prison.
You may well be very happy for your DNA to be used in this way, but it’s crucial that you’re made aware of this potential use in advance. Currently, only FamilyTreeDNA allows law enforcement access to its genealogy database, and you can opt in or out of this. Always use a unique password and enable two-factor authentication to protect yourself.
You should also be aware that taking a DNA test may bring unwelcome news. A small number of people find out that their father is not their biological father (this is known as “Misattributed Parentage Event” or “MPE”), while some people have discovered that they have a previously unknown close relative, such as a sibling or half-sibling.
I experienced a moment of shock when I received a very excited email from one genealogy company claiming they’d found an immediate family member for me. It turned out to be my only sibling, whose test just happened to be processed much faster than expected.
Solving family mysteries through DNA testing
Personally, I believe that the benefits of DNA testing far outweigh the concerns. I’ve managed to help many adoptees identify a birth parent or parents in Ireland through DNA testing.
I also used DNA results to solve two major family history mysteries of my own – one of these concerned the discovery of the puzzling origins of my great-great-grandfather, George Walters, in Liverpool (read the full story here).
When it comes to solving a family mystery, success often hinges on whose DNA is in the company’s database that you’ve chosen to conduct your DNA test. In some cases, it may become necessary to transfer your DNA results to other databases. It’s worth noting that while this can be done for free with MyHeritage and FamilyTreeDNA, it’s not an option with Ancestry or 23&Me. The person who can help you solve your family mystery may be waiting in another database!
If you don’t have a specific mystery to solve, there’s still plenty to get your teeth into with the results of your DNA test. These results are generally broken down into two categories: ethnicity estimate and DNA matches.
The ethnicity component is the heavily marketed angle – how Irish are you?
An amusing advertisement from Ancestry, which was broadcast in the UK after Brexit, played on the idea that although they were leaving the EU, the average British person’s DNA is 60% European.
However, the analysis of your DNA’s ethnic origins is essentially just a percentage estimate based on population reference groups residing in a particular region today. It’s a guide at best. Nonetheless, when you look at your ethnicity data, if you spot a high but unexpected percentage estimate, then it may be a clue to something.
This happened to a client of mine who was searching for their birth father, who was presumed to be Irish. It was revealed through a DNA test that my client possessed 47% Welsh ethnicity and ultimately, we confirmed that their biological father was from Wales, not Ireland.
From a genealogical research perspective, the DNA matches are the real gold. I’ve seen my family tree grow from about 1,000 people to over 4,000 since I started using DNA tests. This involved asking family members – including my parents, aunts, uncles and my parents’ cousins – to take tests for me. If you’re doing this, you must ensure that the tester understands what you’re asking of them – informed consent is key.
It’s incredibly satisfying to make connections with distant relatives. I had a young girl called Mary Bradley in my family tree, orphaned at just 10 years of age in 1886. She was the niece of a paternal great-great-grandfather. I couldn’t find her in any records in Ireland, so I suspected she had emigrated. One day, a DNA match popped up on that particular part of my tree. The match was in Massachusetts – he had built a partial tree indicating a grandmother named “Molly Bradley”. I dug into the Massachusetts records on Ancestry.com and soon established that she was that 10-year-old orphan. I don’t know how or when she got to America, but she went on to have at least four children and a long life. I was so pleased to restore her line into my family tree.
Getting the most out of your DNA test
While it’s possible to identify distant cousins and verify ancestral relationships through DNA tests, it’s important to understand the limitations of the specific DNA testing service being used and to interpret the results with that in mind.
To get the most out of your DNA results, you’ll need to research traditional genealogical records as well. If you don’t know where to start, I recommend checking out the fifth edition of John Grenham’s book Tracing Your Irish Ancestors, published in 2019. If you prefer online learning, the Irish Genealogy Toolkit website offers excellent tools and tips so you can quickly grasp the basics of Irish genealogy.
You could also try searching YouTube, the Legacy Family Tree Webinars or the back catalogue of videos from RootsTech (the world’s largest genealogy convention held annually in Salt Lake City and online). There are also lots of Facebook groups for Irish genealogy and DNA advice.
If you’re looking for something more hands-on, try your local adult education department or library. I teach a bi-annual class in Malahide, Co. Dublin (click here for more details or to enrol in the course).
Here are my top tips for contacting DNA matches:
- Be specific – some people manage more than one DNA kit, so try something along the lines of: “Your kit for Mary O’Sullivan matches me at 160cM”.
- If your match has created a family tree, look for shared surnames.
- Look for shared matches. Perhaps you recognize someone in your match’s list, which will give you a clue as to which part of your own family tree the match derives. If not, ask the match if they recognize anyone from your list. For example, I had a new match who also shared DNA with my maternal first cousin once removed. From this, I could deduce which set of my great-grandparents to focus on (my maternal grandmother’s parents).
- Be patient – many people test casually and don’t check their messages regularly. You can always send another message.
- Offer to share information – you’re asking them to, so you need to dangle a carrot like family stories or photographs.
Most of all, have fun with this!
Claire Bradley works as a professional genealogist in Dublin. She holds a certificate in family history from University College Dublin and a master’s in the history of the family from the University of Limerick. She regularly lectures to family and local history societies and is the director of Irish Studies at the International Institute for Genealogical Studies. You can visit her website here.
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