Ancestry Testing – Snake Oil for Heritage Hungry Public
Odds are, you or someone you know has recently taken a consumer ancestry DNA test to learn about their family’s background. The at-home ancestry DNA testing industry has exploded in the last decade, largely due to websites like 23andMe and Ancestry, which claim to provide ‘life-changing’ information about a person’s heritage. Millions of Americans have already taken ancestry DNA tests through these two websites and the handful of other companies out there.
However, the results that ancestry tests provide are not nearly as accurate or definitive as the companies make it seem – and don’t mean what customers think they mean. In fact, several secret shoppers have found that their own DNA sample can elicit different results from different companies – or even from the same company when submitted twice!
Ancestry DNA Testing Is Not the Same as Familial DNA Testing
DNA testing can be used to accurately identify individuals as compared to prior samples from themselves. It’s also well established that DNA tests to determine relationships between people is unquestionably reliable. For familial relationships, the measurement of alleles along the 23 pairs chromosomes are compared in a straightforward and conclusive manner. Paternity testing and other family relationship DNA tests performed by companies like Health Street have over a 99.9% accuracy.
Further, verified results from legal DNA tests are permissible in court and used by officials in a variety of situations, including such weighty matters as immigration, wills, and estates. Ancestry DNA tests, on the other hand, use a completely different laboratory method to produce estimates of ones ethnic background. Think astronomy versus astrology.
Results of Ancestry DNA Testing Are Always Relative
Each ancestry company has its own proprietary algorithm for coming to its “findings”. That alone should tell you that this is not exactly a settled science. Moreover, they all base their analysis on a comparison of known DNA sets – in other words, the set of DNA that they have gathered from other customers. So, it stands to reason that each company has a different comparative set, and thus, will provide a different result.
Ancestry tests compare a tiny portion of your genome to the same tiny portion of other people’s DNA codes that they happen to have on file. Tiny is the operative word here: let’s not forget, the human genome is massive. When a bit of your DNA matches up with a group of the company’s prior clients’ common DNA, the company classifies you as part of that group.
The percentage of your ancestry that allegedly comes from that group depends on how many of your genes match and whether your DNA shows any telltale markers associated with the group or region. This comparative analysis forms the basis for ancestry DNA test results. Fair enough. But unfortunately, trained geneticists don’t rely on this simple comparison, and neither should you.
Test Findings Are Estimates and Statistical Probabilities – Not Facts
Companies selling the tests have created proprietary maps and databases of DNA sequences from around the world to compare their results. Because the databases are composed of DNA code and sequencing from other clients who are predominantly white Americans and Europeans, current datasets disproportionately represent these groups.
Just think for a moment about how skewed that is! It means that a client is more likely to be deemed of European heritage simply because these companies have more European DNA already held in the database. As a result, the outcomes of ancestry DNA tests can vary wildly according to which dataset is being used for comparison, which company is doing the analysis, and the overall algorithm of the testing company.
Harvard geneticist Robert Green sums up the situation:
“You’re creating different algorithms and you’re using different data sets as your reference points, so it makes sense that you’re going to get some different responses. It’s not that one’s wrong and one’s right. It’s that there isn’t an agreed-upon approach to pick the right number of markers and combine them mathematically. Everyone is sort of just making it up as they go along.”
Geographic and Group Designations Are Unclear and Often Arbitrary
Every consumer genetic testing company designates their own geographic regions and social groupings for analysis. Some companies go as far as telling a customer the very city their DNA has come from, but most stick to associating genes with regions (like Northern Europe), counties (like Sweden), or ethnic groups (like Vikings). How companies choose these groups and what information is used as criteria to be considered as a member of a group is not shared with clients. With no transparency and few if any accepted definitions of standards across companies or datasets, the results can seem entirely arbitrary.
Shockingly, heritage testing companies completely fail to take time and historical migration patterns into consideration when issuing their reports. While some major companies attempt to put a timestamp on many ancestral connections, this information is wildly speculative.
Saying that a person has Italian ancestry, for example, because their DNA matches most closely with people in current day Italy does not take into account the centuries of migration that have transformed the people of that country. This omission ignores where modern day Italians may have come from, even just a couple generations ago, making the baseline DNA grouping for ‘Italians’ or any other ethnicity suspect at best.
As geneticist and author Adam Rutherford put it:
“They’re not telling you where your DNA comes from in the past. They’re telling you where on Earth your DNA is from today.”
If ancestry DNA tests took into account the movement of people over time and place, they could more accurately trace a person’s family line. Ethnicity plays out over centuries and millenia. After all, if you go back far enough, we all came from Africa.
Conclusion: Stay Away from Ancestry Tests
The so-called science behind ancestry DNA testing is simply not what many heritage test websites would like customers to believe. While experts agree that these tests can be analyzed by professionals and statisticians in some cases, the run of the mill reports that are generated by the online companies are riddled with estimates, predictions, guesses, and the poorly understood whims of statistical probabiliites.