Understanding DNA Ethnicity Estimates
As an experienced but amateur genealogist, I am frequently asked which DNA testing company is best. One of the first things that I inquire and probe about are the person’s reasons and purpose for taking a DNA test, and the usual response is the desire to simply receive an ethnicity estimate. There are several key factors that need to be understood so that expectations are properly set. The first is the recognition of basic common sense. Some treat a DNA test flippantly as a novelty, whereas it should be treated deliberately and soberly, as some have made life changing family discoveries from DNA matching. The photo shown above is a stock photograph, which was source here and was edited via Adobe Photoshop Elements.
There are actually three different types of tests available in the DNA marketplace, which are an Autosomal DNA (atDNA) test, a Y-Chromosome DNA (Y-DNA) test, and a Mitochondrial DNA (mtDNA) test. The most commonly used and most affordable type of DNA test is an Autosomal DNA (atDNA) test, which provides an ethnicity estimate and DNA matching. The other two types of tests are only offered by selected companies, and are intended for advanced genealogical research. The Y-Chromosome DNA (Y-DNA) test can only be taken by a male family member, and examines the Y-Chromosome which is transmitted from father to son, generation by generation, and enables the tracing of a common paternal ancestor. The Mitochondrial DNA (mtDNA) test can be taken by anyone, and examines the Mitochondrial DNA which is transmitted from mother to child, generation by generation, and enables the tracing of a common maternal ancestor.
The most common reason for taking a DNA test is to simply receive an ethnicity estimate, and this type of use case could be referred to as novelty or recreational. This is because the user frequently has no intention of actually researching their family tree, such as through the application of their DNA matches to traditional paper trail research. Any of the testing providers of an Autosomal DNA (atDNA) test, such as AncestryDNA and 23andMe, will provide an ethnicity estimate. My experience and observation is that most usually don’t realize the following three key things about ancestry DNA ethnicity estimates.
DNA ethnicity estimates will vary between testing providers.
DNA ethnicity estimates will vary between siblings.
DNA ethnicity estimates will update over time.
Misconceptions originate from the mainstream media, which inaccurately portray DNA as being exact in all regards, as well as the marketing hype from DNA test providers, as they need to simplify the messaging for advertising purposes. All too frequently, there is disappointment after someone takes a DNA test, as well as many resulting questions, so it is my hope that some may find this article informational before they decide to take a test. The information below is first hand and originates from my own results, as I’ve taken tests from multiple test providers, and had multiple family members tested.
DNA Ethnicity Estimates Will Vary Between Testing Providers
Most don’t realize that an ethnicity estimate is only just that, an estimate, and an inexact and wide ranging estimate. The marketing hype and advertising from the testing providers will highlight someone saying that they are 43% of something, but they are simplifying the subject matter for a 20 or 30 second television commercial. Unfortunately, this is somewhat misleading, as the ethnicity percentage breakdown from a DNA test can’t be deciphered with a high degree of certainty. Similarly, DNA is inaccurately portrayed in television and movies. For example, DNA matching can’t decipher an exact relationship, and can’t tell the difference between a niece, nephew, grandchild, aunt, uncle, grandparent, etc.
The methodology used to determine a DNA ethnicity estimate varies between the DNA testing providers, and as a result, it should be expected that the estimate will vary between the testing providers. Each testing provider compiles algorithm based historical reference panels, and simply compares the DNA of someone being tested with those reference panels. Most of the testing providers state their reference information analyzes back roughly 500 years. As a first hand demonstration how DNA ethnicity estimates will vary between testing providers, below are my estimates from AncestryDNA, 23andMe, and FamilyTreeDNA. These ethnicity estimates are as of December 2019, and they have been updated over time for the reasons explained further below.
The only way to determine your ethnicity with any degree of certainty is to perform a traditional paper trail research of your family tree, which can be combined with the the careful application of DNA matches. My extensive paper trail research shows that I’m nearly one-half British, along with Polish (1/4 or 25%), German (1/8th or 12.5%), Swedish (1/8th or 12.5%), and a splash of both Irish and French. When the above ethnicity estimates are compared in the light of my paper trail research, this provides a comprehensive first hand demonstration of the degree of accuracy in which an ethnicity estimate should be evaluated.
DNA Ethnicity Estimates Will Vary Between Siblings
Besides not realizing that DNA ethnicity estimates will vary between DNA testing providers, many do not realize that DNA ethnicity estimates will also vary between siblings, even when the siblings are tested from the same DNA test provider. The following table provides a first hand example of the type of variation that should be expected to occur when comparing DNA ethnicity estimates between siblings. The table shows the AncestryDNA ethnicity estimates of my late father and his three siblings side by side. Note the variations between not only the particular percentages, but also the variations between the particular regions which are included and excluded.
One key reason for the variation is the random nature in which DNA is inherited and passed from generation to generation. Each child receives half of their DNA from their father and the other half from their mother. From a simplistic perspective, each child receives a random 50% of their father’s DNA and a random 50% of their mother’s DNA. Due to that random nature of genetic inheritance, each sibling could inherit different segments or markers of DNA that their other other siblings do not have. The following chart is from Ancestry and illustrates of the randomness of genetic inheritance using blocks with letters.
The blocks of letters represent DNA segments or markers, and shows how each child (Gerald, Glenda, and Reagan) inherits a different set and combination of letter blocks than their siblings. This example helps illustrate how each child receives a random 50% of their father’s DNA and a random 50% of their mother’s DNA. This is one reason why DNA ethnicity estimates will vary between siblings, even when they take a test from the same DNA test provider. It should also be recognized that for the purposes of a DNA ethnicity estimate, the DNA of siblings is not compared with each other, and is only individually compared by algorithms with reference panels determined by each DNA test provider.
The randomness of the genetic inheritance of DNA is also important to understanding in regards to DNA matching. If someone begins to research their family tree via traditional paper trail research, DNA matching can carefully be applied in light of that research. There is significant value in having multiple family members tested for the purpose of DNA matching. The reason being is this randomness of genetic inheritance, as quite frequently, distant DNA matches may show for one family member but not another. For example, I had my late father tested, as well as all three of his siblings. There are distant DNA matches which show for one or two of them, but not the others, and this DNA matching is priceless to family tree research.
DNA Ethnicity Estimates Will Update Over Time
Many do not realize that DNA ethnicity estimates will be updated over time. As explained above, each DNA testing provider devises their own algorithm based reference panels to calculate a DNA ethnicity estimate. The methodologies vary by DNA test provider, and are still evolving. As more and more people get tested, and as those methodologies and algorithms are improved, the expectation should be that your ethnicity estimate will be updated over time. For example, my ethnicity estimates from AncestryDNA, 23andMe, and FamilyTreeDNA have all been updated multiple times. The following table provides a first hand example of how DNA ethnicity estimates will be updated periodically. This table actually serves a dual purpose, as it shows the AncestryDNA ethnicity estimates of my late father and his three siblings horizontally side by side, and vertically captures how each may have been updated at four different points in time.
If your only intended purpose for taking an ancestry DNA test is to get an ethnicity estimate, you should now recognize that the estimate will vary based on testing provider, that the estimate will vary between siblings, and that the estimate will be updated over time. This largely serves as the overall intent of this article. Beyond the novelty or recreational aspect of having an ancestry DNA test done, hopefully you will eventually gain some interest in researching your family tree. Besides getting myself tested, I’ve had seven other family members tested with AncestryDNA. Rarely do I even look at the ethnicity estimates, as the true and long term value is the application the DNA matches to my research.
As to answering the proverbial question as to which test is better, there are multiple dependencies. For solely an ethnicity estimate, 23andMe currently is stated to have the most reference groups and regions from which they draw and devise their estimates. Some testing providers also have additional features to consider, which may or may not be of interest, such a trait and health analysis. If you think that you might have a future interest in researching your family tree, that is where I would strongly recommend AncestryDNA. There are features on Ancestry to directly integrate a family tree with DNA matching. Additionally, roughly twice as many people are said to have been tested on Ancestry, so if DNA matching will be of interest, there should be a significantly greater number of matches on Ancestry. For additional reference and reading, I’m including links to several helpful articles below.
Ancestry: Unexpected Ethnicity Results
Ancestry: What is Genetic Inheritance?
Family Tree Magazine: Fact or Science Fiction? Putting DNA Rumors to the Test
Genealogy Explained: 23andMe vs. AncestryDNA
Genealogy Explained: Do Siblings Have the Same DNA?
Should you any questions, comments, or corrections, please feel free to e-mail me or make a comment below. Again, I make no claim of being a genetic subject matter expert. I’m simply an experienced but amateur genealogist, and attempted to summarize some information which I believe to be accurate and helpful.