When asked about how database size affects ancestry results, David Nicholson, co-founder of Living DNA, told us, “The tests absolutely rely on the reference database. If you have Polish ancestry but there are no people in the database who are Polish, then what the test will do is show what the next closest group is next to Polish, like German or Eastern European ancestry.” Each ancestry DNA service has its own sample database and reference panel made of the DNA samples collected from their users and information collected from sources like the 1000 Genomes Project. The database consists of all this information collectively. A reference panel is made of certain curated samples with known family history and roots in a specific place. The services use insights gleaned from the reference panel to give you geographical ancestry results. In theory, a larger database leads to more information available to create a good reference panel, which then leads to better results for customers.  
A friend of mine knew I had been working on my family history and bought me an AncestryDNA kit for my birthday. My results were surprising to say the least. I discovered I’m 35% Native American, 5% African and 29% from the Iberian Peninsula. This has drastically broadened the way I think about my identity and heritage. I feel connected to those parts of the world now and I’m excited to see how far back our records can go.
Every company providing DNA testing has their own database of DNA samples. These are called AIM’s or ancestry informative markers. These markers were derived from the current populations of America, Asia, Europe and Africa. Every database is looking for a pair of genes located on a specific chromosome in a specific position. The way the DNA is evaluated is through the SNP’s or the single nucleotide polymorphisms. The SNP’s are chosen according to the frequency in a specific geographical population. Your SNP’s are compared to the most common SNP’s for the various populations in the company’s reference database. The results are not conclusive because they are based on common genetic variations. The probability for your DNA being from a certain country is based on a comparison between your DNA and the database. If you used a different company, they would have a different database. This means your results would most likely differ. According to studies, the lowest concordance is with individuals of South Asian, East Asian and Hispanic descent.
A friend of mine knew I had been working on my family history and bought me an AncestryDNA kit for my birthday. My results were surprising to say the least. I discovered I’m 35% Native American, 5% African and 29% from the Iberian Peninsula. This has drastically broadened the way I think about my identity and heritage. I feel connected to those parts of the world now and I’m excited to see how far back our records can go.
23andMe started out by testing for genetic markers of diseases and medical conditions before rolling that back in response to the governmental concerns. It has since started slowly adding more health-related features with approval from the FDA. In April, 23andMe got approval to offer risk analysis for ten genetically linked diseases. The company now offers two options: Health + Ancestry ($199) and Ancestry ($99). The Health + Ancestry plan includes testing for genetic health risks and carrier status, as well as reports on your genetic weight, hair loss, and other traits.
This is a large amount of data not being used by services testing DNA. There are millions of SNP’s contained in your DNA. This type of testing only looks at specific variations. This requires between 100 and 300 AIM’s. This is a small fraction of the SNP’s differentiating DNA. This means if your test stated you are fifty percent European, it means only half of your SNP’s appear to be European. Another issue is certain markers used for ancestry information for any given test are only derived from either your Y chromosomes or your paternal line or your mitochondrial DNA or maternal line. When these markers are used, your test will be less accurate. Another flaw is the DNA testing services are obtaining DNA from the current populations in specific regions. This makes unsubstantiated conclusions that the people living in these areas hundreds of thousands of years in the past have had the same DNA for all these years.
23andMe started out by testing for genetic markers of diseases and medical conditions before rolling that back in response to the governmental concerns. It has since started slowly adding more health-related features with approval from the FDA. In April, 23andMe got approval to offer risk analysis for ten genetically linked diseases. The company now offers two options: Health + Ancestry ($199) and Ancestry ($99). The Health + Ancestry plan includes testing for genetic health risks and carrier status, as well as reports on your genetic weight, hair loss, and other traits.
Gteat article! Thank you so much. I am Jewish American. Both sides of my family immigrated from Eastern Europe/Russia about 5 generations ago. I would really like to try and find out more about exactly where they came from, identify potential living and deceased distant relatives in the USA and abroad and ultimately start creating an extensive family tree. Which test would you suggest?
When my results appear, they show nothing bad. If anything, it’s anticlimactic: cholesterol, vitamins, liver proteins and the like are all in the normal range, with only ferritin (iron stores) slightly high, with a recommendation to go easy on any iron supplements. My problem with the baseline test is that, unlike Thriva’s other products, clients are supposed to have one every three months to keep track, but would I really want (or indeed need) to do such a test so regularly?
“My concern is that more and more of these tests are being put out, and people are being persuaded to have these tests done, and they get results back that are very often of very low value and dubious helpfulness,” she says. “And often people are told to go to see their GP and that then places a direct stress on the NHS, at no cost to the company. The companies make their profits and walk away, letting the NHS sort out all the fallout, the push-back, from the test results, in a way I find absurd. Why should the NHS have to prop up the problems that these companies create?”

If this individual used several different companies for DNA testing, they might get an idea as to their past origins based on the moderate or high similarities of the people currently living in different regions throughout Africa. This is only possible if the companies have established the correct reference populations. This person must understand their DNA is being matched to the current population as opposed to the people who occupied the region hundreds of years in the past. It is just as possible the results would state this African-American individual is 75 percent European. This is because the ancestry markers chosen are only for a small percentage of this individual’s DNA. The African population has a more genetic diversity in itself than a European population and an African population.
Most of the services we tested use genotyping to read your DNA. Genotyping looks for specific markers in your genetic code. For something like ancestry testing, genotyping is effective because it identifies known variants in your DNA. Scientifically speaking, genotyping’s weakness is that it can only recognize previously identified markers. This is one reason DNA tests’ accuracy relies so heavily on the DNA database size; there must be enough information available and identified genetic variants in the database to recognize new customers’ markers.
I am not sure how Ancestry get their results. Mine is 49% British and 49% German. This means one of my parents must have been British and the other German. I moved to the UK 15 years ago. But both my parents where German as where my 4 grandparents and my 8 great-grandparents. It seems to me they have rolled the dice and assumed that if you send a sample from the UK you must have British ancestry. No science behind it at all. I could have gone to the oracle at the fun fair.
You might want to stay away from DNA tests if you or any of your close relatives have committed a crime. Although ancestry DNA testing companies don’t typically share database information with law enforcement, consumer DNA tests may result in future identification. For example, FamilyTreeDNA, which has a database of close to a million samples, has agreed to give the FBI limited access to the company's DNA database. This access consists mainly of consumer-level insights, like matches with other members of the FamilyTreeDNA community who have enabled family matching; by law, however, more in-depth investigation requires a subpoena.
There is a TV show called Long Lost Family on TLC that uses Ancestry DNA and records to identify and locate families. I am not an adoptee but have taken tests with Ancestry and Family Tree DNA. I think using the Ancestry test would be better to help identify your birth parents since you could view your close matches and their family trees (if public). You can also download the raw data from Ancestry, FamilyTree, or 23&Me and upload them to gedmatch. Gedmatch is a free site where test-takers from different companies can compare results/matches without having to test with all three companies.
“My concern is that more and more of these tests are being put out, and people are being persuaded to have these tests done, and they get results back that are very often of very low value and dubious helpfulness,” she says. “And often people are told to go to see their GP and that then places a direct stress on the NHS, at no cost to the company. The companies make their profits and walk away, letting the NHS sort out all the fallout, the push-back, from the test results, in a way I find absurd. Why should the NHS have to prop up the problems that these companies create?”
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