I am struggling to interpret the results of an Autosomal DNA Test with MyHeritage and a Y-DNA 12 Test with Family Tree DNA.
First, the MyHeritage ethnicity result suggests that I have 10.3 per cent Italian DNA. The estimates of English, Irish, Scottish and Welsh are all documented in my family tree, but not Italian. In contrast, the Family Tree DNA results suggest that my DNA is 53 per cent British Isles, 45 per cent Western and Central European and 2 per cent Scandinavian.
I uploaded the results to DNA.Land, which gave a completely different breakdown: 74 per cent North-West European, 18 per cent South/Central European and 7.3 per cent North-East European (of which 5.5 per cent is Finnish); the rest is deemed ambiguous. How accurate are these results? Should I be looking for Italian ancestors?
Name withheld

This question relates to two different types of DNA test. The Y-DNA test traces the all-male line, thereby mimicking the pattern of surname inheritance – the test is best used in the context of a dedicated surname project. A 12-marker test is a low-resolution test, so I recommend an upgrade to 37 markers to get matches that are more likely to be genealogically relevant.

The ethnicity estimate from Family Tree DNA (FTDNA) comes from the MyOrigins report included with its Family Finder test, not from the Y-DNA test.

The MyHeritage and Family Finder tests are autosomal DNA tests, which provide information on all your ancestral lines.

There are five main companies that offer autosomal DNA tests (see my article at bit.ly/WDYTYADNA). While their population percentages can be fun, they generally have little practical genealogical utility, so are best used for cousin matching in genetic genealogy databases.

DNA.Land is a third-party service where you can upload results. It might be interesting to experiment with other free services such as gedmatch.com and gencove.com, but do check their privacy policies first.

Ethnicity or admixture tests are more properly known as biogeographical ancestry tests. They compare your DNA to reference populations and tell you how much of your DNA matches each population. The populations are taken from publicly available datasets and complemented with the companies’ own proprietary databases. Since each company has a different dataset, it’s not surprising that results differ.

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Note too that you’re being compared with the DNA of living people. Present-day populations are not necessarily a good proxy for historical populations. A company’s website should reveal which reference populations are being used. If your populations aren’t included in its datasets, then you can only be matched with the closest populations.

The algorithms also vary. Some firms look at ancestry informative markers – single unlinked markers scattered across the genome that are found at high frequencies in specific populations. Others look at linked markers or segments of DNA that are commonly found in certain populations.

Large shared segments of DNA indicate recent ancestry, but small shared segments and ancestry informative markers can date back millennia. This means that the tests are focusing on different time depths. Some give information about your ancestry within the past few centuries; others provide percentages relating to your ancestry from thousands of years ago.

As for the interpretation, these population percentages are generally only accurate at the continental level. Jewish heritage can also be reliably detected with most of the current tests. The regional and country-level assignments do not correspond well with known genealogies, especially for smaller percentages, and vary between companies.

However, some company reports are more accurate. AncestryDNA’s (dna.ancestry.co.uk) genetic communities feature (renamed ‘regions’) can assign people to sub-regions (eg Southern England, Ulster, Scottish Highlands) with reasonable accuracy. The Living DNA test provides sub-regional resolution within the British Isles, and the larger percentages mostly correlate well with known genealogies. Companies are always improving their products and adding to their reference populations, so we can expect our results to be updated.

Regarding your autosomal DNA results, the results are consistent with ancestry from Northern Europe. The regional percentages are not accurate, and are not relevant for genealogical research – they are described as estimates for a good reason. If there really were any recent Italian ancestors, you would expect to see Italian surnames showing up in the match lists.
DNA testing works best when used with genealogical records, so correspond with your matches and compare trees.

Debbie Kennett is the author of DNA and Social Networking and The Surnames Handbook