Opinion: Why DNA ancestry tests have questionable results

Autosomal DNA ancestry testing
Autosomal DNA ancestry testing Photo credit: Getty Images

OPINION: When a leading genetic anthropologist told me autosomal DNA ancestry tests can be misleading to many people, I felt a sense of relief. 

As a kid, I had an obsession with genealogy and was lucky enough to be able to trace most sides of my family back to the 1500s.  

But when I decided to take my first autosomal DNA test with Family Tree DNA, I was upset that my results did not exactly match my documented genealogy.

I decided to try another two tests and also get my father, mother, and maternal grandparents tested with different companies. 

But when each of the results came back, I was even more confused. 

While it showed we are all related (whew), all of us had varied results depending on the company we tested with. 

How could Family Tree DNA tell me all my European ancestry comes from Britain and Ireland yet my maternal grandfather's 23andme results (yes the test confirmed he was my relative) come back as almost 100 percent French and German?

The 23andme test I took, told me around 14 percent of my genetics did come from France and Germany which lined up with my grandfather's results but why the differences between companies?

My mother got her results with AncestryDNA and it showed she was only two percent from Germanic Europe (the category that includes Germany) yet her father was told he was almost all genetically French and German when he tested with 23andme. 

What made it even more confusing was that my maternal grandfather was never told he was French and German. He was born in the United States to parents of Danish ancestry and has identified as Scandinavian American his entire life. 

My father who tested with AncestryDNA has documented recent ancestors from France which was initially confirmed with the results but after a few years, his results "updated" and his entire percentage of Europe West (region that includes France) ancestry was removed. 

DNA Ancestry Timeline / Great Great Grandparents from Denmark
DNA Ancestry Timeline / Great Great Grandparents from Denmark Photo credit: James Fleury

When I tested with the National Genographic Project, I came back as 33 percent Mediterranean yet the other tests said I had no ancestry from this region. 

University of Otago professor of biological anthropology Lisa Matisoo-Smith told me these autosomal DNA ancestry tests can be "misleading" for people as she claimed there are no biological markers that can assign people to any specific population with anything even close to 100 percent accuracy. 

She said while the DNA markers are real and there is a chance, given a combination of specific markers that someone's ancestry is from a particular region, there is no way of being 100 percent certain the markers are specific to that area and claimed it is unlikely they are at all. 

Matisoo-Smith said this is because the companies providing these tests have identified what they call "ancestry specific markers" and while they call these markers "specific" they are only found at a higher frequency in particular ethnic groups or regions. 

"Like all biological variation we know there is more genetic variation within groups than between groups, so while they [markers] may be at high frequency in particular populations or groups of people from geographic regions, they are not the only people who would carry those markers."

She also added that not everybody from those regions would carry the same markers either.

However, 23andme claims their "ancestry service" results are "highly accurate" and can provide "estimates" of ancestry percentages down to 0.1 percent. 

"Customers can select different confidence thresholds ranging from 50 percent to over 90 percent confidence," according to a statement provided to Newshub. 

Ancestry composition confidence levels
Ancestry composition confidence levels Photo credit: James Fleury

When I eventually found the option to change my ancestry composition to "90 percent confidence" I was shocked. 

I went from being assigned 85 percent British and Irish ancestry to being 40 percent "Broadly Northwestern European" when I changed the confidence level from 50 percent.

It confirmed what Matisoo-Smith had told me about the markers, 23andme is only 50 percent sure I am 85 percent British and Irish and they can really only tell me they are 90 percent sure I am "Northwestern European." They can't tell me with 100 percent certainty I have ancestry in those regions. 

In a statement provided by AncestryDNA, they said they agreed with Matisoo-Smith there are no single genetic markers that can assign people to a population. 

However, the company claimed their "statistical model" doesn't look at single genetic markers when making ethnicity estimates. 

"We combine information from hundreds of thousands of genetic markers."

"In addition, we look at markers as sets rather than as individual markers which improves the overall power of prediction."

What does "power of prediction" mean? Do people know their ethnicity estimate is just a "prediction?"

Matisoo-Smith said most people who take the tests likely do not read the fine print that describes the science behind the results. 

She said for the companies to be ethically correct, they should market the products differently. 

"Are they telling the truth? That's questionable. Are they misleading the population? Yes, I think they probably are."

Matisoo-Smith explained the reason I had received varied results from the different companies was because of the difference in algorithms and the variation of demographics of people who had tested at each company. 

"If you are looking at 23andme, that's based in the United States so that's going to have mostly Western European, West African, Native American maybe some Mexican."

"AncestryDNA has an Australian-based office and so they are going to be drawing potentially more Polynesian DNA than North America."

However, despite the differences in ways the genetic data is interpreted between companies, Matisoo-Smith said the varied results between tests should be an indication of how reliable the tests are. 

"I think one way of looking at it is the more specific they are getting with their descriptions of your ancestry, the less reliable they are."

The genetic anthropologist said that even if more people were aware of how these tests work, "people believe and see what they want to see". 

It is estimated 30 million people worldwide have taken an at-home ancestry test making this a pretty lucrative business. 

FTDNA and The National Genographic Project did not respond for comment.