CRI Genetics DNA Test Education: How does Ancestry DNA testing work?

Here's how your Ancestry DNA Test results are calculated... It's a little simple, a little complicated, and a whole lot of fun!

I’m glad you asked.

You’re not going to believe just how simple this is…

At the CRI Genetics lab, we have a really, REALLY big hat.

It’s a hat you could swim in, if we filled it with water...

But, we’re NOT going to fill it with water…

Because inside that really big hat, we have several thousand tiny little pieces of paper…

Each tiny piece of paper has an ancestry written on it. British, German, Yoruba, Italian, etc…

All the ancestries we cover here at CRI Genetics, all written on tiny pieces of paper in a giant hat.

When a DNA test arrives at the lab, CRI Genetics scientists throw the DNA sample in the trash. Then they count 1,000 tiny pieces of the paper out of the hat at random.

That’s why it takes a few weeks to get your reports. It takes our scientists a long time to pull all the papers out and calculate the percentages.


That’s not how it works at all.

Here’s where your Ancestry results REALLY come from:

Almost all the ancestries covered at CRI Genetics are attached to regions around the world. British, German, Yoruba, Italian, etc…

There are people who live in these regions today… People who took a DNA test.

Some of the DNA tests were a part of large-scale genetic studies of populations. These are situations where scientists called on volunteers to take a DNA test in order to study genetic patterns in DNA.

If we use Italian as an example here… Someone who participated in the study would have to be born in Italy. A participant would typically also have to prove their family lived in Italy for at least two generations.

Once scientists had a significant number of DNA samples from Italian individuals with documented Italian heritage, they would identify common patterns in the DNA, patterns that appear to be distinctly “Italian.”

Finding a common pattern in one population’s DNA does not necessarily mean that the pattern “belongs” to that population, however…

For that, scientists need to study patterns from multiple populations, then compare and contrast. They identify common patterns in “Italian” DNA that are not common in “British” DNA and vice versa. They also identify patterns that “Italian” and “British” DNA appear to share that are not common in other regions around the world.

Many of these large-scale genetic studies are publicly available. One large-scale study that almost all DNA testing companies use to some extent to calculate their results can be found HERE.

The linked study above is just one example.

Most (if not all) DNA testing companies do some studying of their own, including CRI Genetics.

The more DNA samples scientists from various regions scientists can study, the more accurate and precise DNA tests get.

I can’t speak to how other DNA testing companies use customer DNA to improve their algorithms, but I can tell you CRI Genetics uses surveys.

CRI Genetics runs surveys where customers voluntarily share some details about their family history: Where they were born, where their parents were born, where their grandparents were born, and the known ancestries for all the people mentioned, to the best of their knowledge.

Again, this is totally voluntary. If a CRI Genetics customer doesn’t want to share that information—or doesn’t want CRI Genetics scientists studying their DNA like that—then they don’t take the survey.

This way, CRI Genetics scientists can continue to compare and contrast genetic patterns in DNA from regions around the world and identify more patterns that are specific to certain populations.

CRI Genetics also has scientists (such as Alexei Fedorov) leading and participating in more large-scale genetic studies around the world that don’t involve CRI Genetics customers, but which contribute to the CRI Genetics algorithm nonetheless.

Back to the question of where YOUR ancestry results came from…

CRI Genetics scientists compare your DNA to the DNA of all the other samples they have access to. They identify patterns that are known to be connected to various regions.

There are other factors considered, such as mass migrations throughout history that affected genetic patterns. The bulk of the algorithm is still based on comparing, contrasting, and matching those patterns.

There are complications with this that are very difficult to overcome…

Some regions of the world have so much genetic overlap that it’s very difficult to distinguish individual countries from each other. Northwestern Europe is a prime example.

As mentioned in a previous CRI Genetics DNA Test Education blog post, DNA doesn’t care about current country borders…

There have been many migrations due to wars, disease, and simple economic trade in Northwestern Europe in the last couple thousand years. Because of this, almost everyone with German DNA also has some degree of French and British DNA (and vice versa on all accounts). This is the case even if there are no known ancestors from those other countries.

There are some countries that aren’t even listed in CRI Genetics ancestry results (and other DNA testing companies) simply because the genetic patterns are the same as others. The genetic differences between the populations of Belgium and France or Austria and Germany are so minimal that they’re essentially indistinguishable.

This is the case for many ancestries and populations around the world.

If you have Italian ancestry, it stands to reason you have some Spanish and Greek DNA as well, even if you have no known Spanish or Greek ancestors. Mediterranean nations have intermingled for as long as Mediterranean nations have existed.

If you have Gujarati Indian ancestry, it’s not unreasonable to expect ancestry from other populations in South Asia, such as Bengali or Punjabi.

Many East Asian populations, like Japanese or Vietnamese, likely have at least a small bit of Chinese ancestry.

Any time you see the ancestry results of a DNA test, it’s important to keep the history of human migrations in mind.

I personally know a Filipino man who was shocked to find a significant percentage of German ancestry in his results. All his known ancestors are Filipino like him. He wasn’t expecting his results to say “100% Filipino” (because no one is “100%” anything 😉). If he was to get a large percentage of any European ancestry, he expected Spanish, based on the colonial history of the Phillipines. However, the Spanish had to compete with the Dutch for control of the Phillipines. While the Spanish won the conflict, the Dutch Empire was still influential in the region. Dutch ancestry would show up on a DNA test as “German” (due to factors previously discussed), so it’s likely my Filipino friend has one or more Dutch ancestors from the colonial days. These ancestors would be too many generations removed for most families today to remember them.

When you think about all the migrations in human history, whether for war or trade or colonization or even to escape from plagues and famines…

It makes many of the “surprises” in DNA tests feel hardly like surprises at all.

What CRI Genetics loves most about DNA testing is the constant reminder of this truth: We’re all unique individuals with diverse opinions and backgrounds, but we still have so much in common with each other and every corner of the world.