How well do ancestry dna tests actually work?

Commercials abound for DNA testing services that will help you learn where your ancestors came from or connect you with relatives. I’ve been interested in my family history for a long time. I knew basically where our roots were: the British Isles, Germany and Hungary. But the ads tempted me to dive deeper.

Previous experience taught me that different genetic testing companies can yield different results (SN: 5/26/18, p. 28).

And I knew that a company can match people only to relatives in its customer base, so if I wanted to find as many relatives as possible, I would need to use multiple companies. I sent my DNA to Living DNA, Family Tree DNA, 23andMe and AncestryDNA.

I also bought the National Geographic Geno 2.0 app through the company Helix. Helix read, or sequenced, my DNA, then sent the data to National Geographic to analyze.

These companies analyze hundreds of thousands of natural DNA spelling variations called single nucleotide polymorphisms, or SNPs. To estimate ethnic makeup, a company compares your overall SNP pattern with those of people from around the world. SNP matches also help companies see who in their database you’re related to.

Some of the companies also analyze a person’s Y chromosome or mitochondrial DNA. Y chromosome DNA traces a man’s paternal line. In contrast, mitochondrial DNA traces maternal heritage, since people inherit mitochondria, which generate energy for cells, only from their mothers. Neither type of DNA changes that much over time, so those tests usually can’t tell you much about recent ancestors.

Once I sent in DNA samples, my Web-based results arrived in just a few weeks. But my user experience, and results, were quite different for each company.

National Geographic Geno 2.0

How Well Do Ancestry DNA Tests Actually Work?MOTHERLINE National Geographic Geno 2.0 shows how a customer’s maternal line migrated and changed across time, as determined by analyses of mitochondrial DNA. A heat map indicates where members of your maternal line are most prevalent. National Geographic Geno 2.0

At $199.95, National Geographic’s test is the most expensive, yet the least useful. The results are generic, and the ethnicity categories are overly broad. My results say that 45 percent of my heritage came from people living in southwestern Europe 500 to 10,000 years ago. That doesn’t tell me much and doesn’t reflect what I know of my family history.

Pros

  • Specialized for looking into the deep past

Cons

  • Provides no ancestry information within the last 500 years

There’s no relative matching, though Geno 2.0 shows which historical “geniuses” may have shared your mitochondrial or Y chromosome DNA. I don’t know how National Geographic knows about the mitochondria of Petrarch, Copernicus or Abraham Lincoln.

So I’m skeptical that I am actually related to those famous figures, even from the distance of 65,000 years, the last time we supposedly had an ancestor in common. The service also calculated the percentage of Neandertal ancestry that I carry. I take geeky pride that 1.5 percent of my DNA comes from Neandertals, topping the 1.

3 percent average for Geno 2.0 customers.

Overall, Geno 2.0 has a nice presentation, but I learned more about my family history elsewhere. Since I bought the Geno 2.0 kit as an app through Helix, I don’t know if the kit purchased directly from National Geographic, which is processed by Family Tree DNA, would yield different results.

Living DNA

How Well Do Ancestry DNA Tests Actually Work?ENGLISH ANCESTRY Living DNA offers fine-scale ethnicity estimates for people of British or Irish descent (Saey’s results shown). The company is less certain about subregional estimates than it is about global estimates. Living DNA

Another expensive test ($159) came from Living DNA. When I saw the company’s ad claiming to pinpoint exactly where in the British Isles a person’s genetic roots stem from, I decided to give it a go. The company highlights ethnicity on a world map, then lets you zoom in from the continent level. I found that 22.5 percent of my heritage came from Lincolnshire in east-central England. I haven’t yet traced any ancestors to Lincolnshire, but I did find through much genealogical sleuthing that one of my sixth-great-grandfathers came from Aberdeen, Scotland. Living DNA says that 3.1 percent of my DNA is from Aberdeenshire. Written narratives on the website provide a history of each reported region.

Pros

  • Offers detailed ethnicity estimates for people of British or Irish descent

Cons

  • Can’t link relatives to a family tree

Using mitochondrial DNA and, if applicable, Y chromosome DNA, the company can trace your maternal and paternal lines back to human origins in Africa and show where and when your particular line probably branched off the original. My “motherline” probably arose in the Near East 19,000 to 26,000 years ago, Living DNA claims, and my ancestors were some of the first people to enter Europe. In February, the company announced that it would soon launch a relative-matching service for its customers.

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I’m not sure the service would be worth the price tag for people whose ancestry doesn’t contain a strong British or Irish tilt, though Living DNA says it is working to improve ethnicity estimates in Germany and elsewhere.

Family Tree DNA

How Well Do Ancestry DNA Tests Actually Work?ANCIENT DNA MATCHES

How Do DNA Ancestry Tests Really Work?

Not long ago, genetic tests that are widely available today were the domain of dystopian science fiction. Now, they're a nice gift to buy your genealogy-minded aunt for her birthday.

Companies such as 23andMe, Ancestry.com and National Geographic market these at-home DNA testing kits, offering to unlock your genetic secrets for the price of a group dinner at a nice restaurant and about half a teaspoon of spit.

And although there was a time when these tests were marketed primarily as health services — ways to test for diseases and better understand your body — that aspect of their branding has partly receded, in part thanks to action from U.

S. regulators. Nowadays, most of the big genetic testing companies pitch themselves primarily as “ancestry” services, promising both to connect long-lost relatives and to tell users what parts of the world their ancestors came from.

How Well Do Ancestry DNA Tests Actually Work?

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How Well Do Ancestry DNA Tests Actually Work?

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“The ancestry service is a collection of features that give you a comprehensive look into your history, from the very ancient past, 60,000 years ago with Neanderthals, up to the recent past,” said Robin Smith, who heads 23andMe's ancestry program.

AncestryDNA® Test Accuracy

 Your AncestryDNA® test results are the product of a multi-step process. First your DNA is measured, or read, in the lab. This lab processing generates raw DNA data. The raw data is then analyzed to generate your AncestryDNA results. There is no single measure of AncestryDNA test accuracy. Instead, the accuracy of each step can be measured independently. 

How Well Do Ancestry DNA Tests Actually Work?

Accuracy of the Reading of the DNA

Reading your DNA is a first step in generating your AncestryDNA results. Accuracy is very high when it comes to reading each of the hundreds of thousands of positions (or markers) in your DNA. With current technology, AncestryDNA has, on average, an accuracy rate of over 99 percent for each marker tested. 

Accuracy of Regions in Your Ethnicity Estimate

When you take an AncestryDNA test, your test results will include an ethnicity estimate. Part of this is an estimate—reported as a percentage—of where your ancestors lived hundreds of years ago, as far back as around 1,000 years. An example would be 8% Italy, which reflects the amount of your DNA that has been inherited from Italian ancestors.  

AncestryDNA determines this part of your ethnicity estimate in two steps. The first step is to collect the DNA of people whose family has a long history in a particular part of the world. This group is called the reference panel, and right now 43 different regions in the world are represented. 

The second part of the process is to compare your DNA, bit by bit, to the DNA of the people from the 43 different regions in the reference panel, to see which groups’ DNA your DNA most resembles. For example, if ten percent of your DNA looks most similar to the DNA of people from France, AncestryDNA will assign ten percent of your ethnicity estimate to France.

AncestryDNA uses a number of different methods to determine the accuracy of this part of your ethnicity estimate. One method looks at how well AncestryDNA predicts the ethnicity estimate of people with a known ethnicity. For example, it looks at how well it works on people from the reference panel (who should theoretically come back with 100 percent of a certain ethnicity).

In terms of particular regions in an ethnicity estimate, the accuracy will—as is true for methods used by other testing companies —depend upon the region/population and the granularity of the prediction.

If AncestryDNA restricts itself to the continental level (Europe, Asia, Africa, etc.), it is extremely accurate. As AncestryDNA drills down further into more specific regions, the accuracy will tend to go down.

So it is a balancing act between accuracy and granularity.

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See Table 4.1 of the Ethnicity Estimate 2018 White Paper for more information on how well the AncestryDNA algorithm does for each region of the reference panel.

The best DNA testing kits available now

A DNA test can jumpstart or augment your understanding of your family history — from identifying close cousins all the way back to your earliest ancestors. Some tests claim to reveal your “ethnicity” — though that's a thorny, controversial topic. And some services can shed light on your genetic predisposition for diseases and physiological traits ranging from eye color to your tolerance for cilantro. 

Over the past 20 years, DNA testing has entered the mainstream, driven by lower prices, higher visibility and improving science. Back in the aughts, a do-it-yourself DNA test cost about $1,000.

But in recent years, the kits have become quite affordable, with a wide range of DNA testing companies — from trailblazers such as Ancestry and 23andMe to upstarts such as Living DNA — offering rather sophisticated analysis of your genetic makeup for as little as $75 — or less, if you can find a deal on Black Friday or during the periodic holiday discounts throughout the year.

How Well Do Ancestry DNA Tests Actually Work?

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There are three types of DNA tests — each with its own particular strengths, limitations and rationales.

  • An autosomal DNA test is the best investment for most beginners; it can identify relatives between five and seven generations back, across both maternal and paternal lines. 
  • Only men can effectively use a Y-DNA test, whichidentifies male relatives on the paternal line reaching back 60,000 years; if you're looking to trace the history of your family's surname, this is the test to use. 
  • And mitochondrial DNA testing, also known as mtDNA testing, can determine genetic relationships on a maternal line from up to 150,000 years ago; both men and women can take this type of test. 

Once you've been tested, each company will present you with an analysis of your geographical origin; some claim to be able to pinpoint a specific country, town or even “tribe.

” Some will also serve up “matches” from their DNA databases, which will give you a head start on connecting with possible relatives, and offer some degree of family tree research support.

AncestryDNA, for example, offers a subscription service that includes access to hundreds of databases containing birth, death and marriage announcements, census documents, newspaper archives and other historical records. 

Some companies sell tests designed for specific ethnicities or specialized kits that claim to shed light on your optimal skin care regimen or weight; others offer tests designed to identify the genetic makeup of your cat or dog. The experts I spoke to were dubious of the efficacy and value of these tests and recommended avoiding them.

Though there's no blood involved with modern DNA testing — you either swab the inside of your cheek or fill a small test tube with your saliva — there are plenty of reasons to be leery of the companies that sell these kits.

Your success in DNA test genealogy is largely dependent on supplying highly personal information about yourself and your relatives — from your genetic data to your mother's maiden name, that traditional cornerstone of password security. 

Concerns over data privacy and security are well-founded, and experts warn that regulation — especially in the US — lags far behind the technology.

And you should know that some DNA testing companies may share data with pharmaceutical companies and law enforcement agencies.

Bottom line: Think critically before volunteering information about your health history and familial connections to any company or organization. 

Read more: In the future, not even your DNA will be sacred

DNA testing, and genealogy more broadly, involves a complicated mixture of genetics, probabilities and guesswork.

The various DNA testing services use different labs, algorithms, equipment and criteria to analyze your genetic material; though you should expect some degree of overlap between analyses from different companies, they may differ significantly.

There's also an element of critical mass — the larger the company's database, the larger the sample they use to analyze your results, and the more accurate your results should be. 

We tried some of the top DNA testing services, assessing the breadth and depth of their offerings, methodologies, reputation and price. Take a look at our recommendations below. And if you've taken any of these DNA tests, tell me about your experience with it in the comments below.

Looking for more in-depth info on DNA testing services in general? Jump to our DNA test kit explainer.

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What is genetic ancestry testing?

Genetic ancestry testing, or genetic genealogy, is a way for people interested in family history (genealogy) to go beyond what they can learn from relatives or from historical documentation.

Examination of DNA variations can provide clues about where a person's ancestors might have come from and about relationships between families. Certain patterns of genetic variation are often shared among people of particular backgrounds.

The more closely related two individuals, families, or populations are, the more patterns of variation they typically share.

Three types of genetic ancestry testing are commonly used for genealogy:

Y chromosome testing

Variations in the Y chromosome, passed exclusively from father to son, can be used to explore ancestry in the direct male line. Y chromosome testing can only be done on males, because females do not have a Y chromosome.

However, women interested in this type of genetic testing sometimes recruit a male relative to have the test done.

Because the Y chromosome is passed on in the same pattern as are family names in many cultures, Y chromosome testing is often used to investigate questions such as whether two families with the same surname are related.

Mitochondrial DNA testing

This type of testing identifies genetic variations in mitochondrial DNA. Although most DNA is packaged in chromosomes within the cell nucleus, cell structures called mitochondria also have a small amount of their own DNA (known as mitochondrial DNA).

Both males and females have mitochondrial DNA, which is passed on from their mothers, so this type of testing can be used by either sex. It provides information about the direct female ancestral line.

Mitochondrial DNA testing can be useful for genealogy because it preserves information about female ancestors that may be lost from the historical record because of the way surnames are often passed down.

Single nucleotide polymorphism testing

These tests evaluate large numbers of variations (single nucleotide polymorphisms or SNPs) across a person’s entire genome. The results are compared with those of others who have taken the tests to provide an estimate of a person's ethnic background.

For example, the pattern of SNPs might indicate that a person's ancestry is approximately 50 percent African, 25 percent European, 20 percent Asian, and 5 percent unknown.

Genealogists use this type of test because Y chromosome and mitochondrial DNA test results, which represent only single ancestral lines, do not capture the overall ethnic background of an individual.

‘It made me question my ancestry’: does DNA home testing really understand race?

Last year, I did what 12 million people from all over the world have done and surrendered my spit to a home DNA-testing company. I hoped a MyHeritage test would bring me the peace I needed; my Irish mother had never been able to give me any information about my biological father.

Raised by her and my white dad, I’d always longed for a country to attribute my blackness to, or for help answering the ubiquitous “Where are you from?” question. I’d spent years making up exotic-sounding combinations to justify my appearance (some days Jamaican-Spanish-Swedish; other days half Brazilian, or half Iranian).

But, at 24, I was done with occupying a box of black ambiguity. Could I finally get a clear answer?

The results arrived by email on a summer’s day last year. I clicked on the “ethnicity estimate” link, which offers an analysis of DNA by country, my heart pounding as I scanned the digital map.

The test showed that my blackness comes from Nigeria; 43% of my DNA, in fact. Then there’s 1% from Kenya, and the rest from Great Britain and Ireland (55%), as well as eastern Europe (1%). I’d often been told I looked east African, or mixed with multiple countries, so I was surprised by what was nearly a 50:50 split.

I began to think my grandmother had had an affair, even my mother. My imagination ran riot. I wouldn’t do it again

I had no cultural knowledge of Nigeria; should I now start claiming it as my own? Did the results mean my very distant ancestors were Nigerian, or that my biological father was probably from there? Why did my features not resemble a typical west African? I felt more confused than ever.

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