Why Your Ethnicity Estimate Won’t Match Your Family Tree

If you have done a DNA test, or you are thinking about doing a DNA test, there is something you should know.  Your ethnicity estimate, no matter which company you decide to test with, will not exactly match your family tree. 

In this article, I’ll explain a little bit about the main reasons that your ethnicity results won’t match your known ancestry.

I got thinking about writing this post after listening to an interview on the radio show “Fresh Air” with Alex Wagner, author of the book ‘Futureface’.  In the interview, Wagner talked at great length about DNA testing and the various things that she learned about her family, which excited me, naturally. 

The idea of using DNA testing and traditional genealogy to explore her biracial ancestry was very interesting, and I love the idea.   The way in which she explained her ethnicity estimates, however, was disappointing. 

The fact that she never even mentioned her DNA matches, which are – in my opinion – the most exciting and useful aspect of DNA testing, left me feeling like she might have missed out on something really great.

The average person who listened to this interview was probably left with a very poor opinion of what companies such as Ancestry DNA, 23 and Me, and Family Tree DNA have to offer.  Ethnicity estimates are called estimates for a reason.

Six reasons why your ethnicity estimate won’t exactly match your family tree

There are a few main reasons why your ethnicity estimate might seem inaccurate or incomplete, and I have listed them here.  If you scroll down, you can find further explanation and more detail about these reasons.

• You only inherited 50% of the DNA that each of your parents have in their genome.
• DNA is not inherited in equal amounts from all ancestors
• You don’t share DNA with all of your ancestors
• DNA testing companies often have different geographical definitions for regions.
• Political borders in many parts of the world have changed significantly over the past few hundred years.
• You might know more about one line of your family, and less about another

#1  Each person inherits 50% of their mother’s DNA and 50% of their father’s DNA

This is the top reason why your ethnicity estimate will not exactly match your family tree.  When you were conceived, you inherited 50% of your mother’s DNA and 50% of your father’s DNA.

This means that 50% of the DNA of each of your parents is not in your genome, and therefore cannot be included in your DNA test results.

Furthermore, your parents inherited 50% of their DNA from each of their parents, too, which means that you only share about 25% of your DNA with each grandparent.  The result of this is that 75% of the DNA of each of your grandparents is basically “missing” from your DNA. 

This is an incredible amount of missing information, if you really think about it.

I like to explain ethnicity estimates as a “snapshot” of the DNA that you inherited from your ancestors, and of course, it cannot be a snapshot of the DNA that you did not inherit. 

The effect on your ethnicity estimate is that if your dad had a Scottish great-great grandfather, there is a chance that you might not have inherited very much Scottish DNA from your dad, since most of his genes that would have matched the Scottish region might have been within the 50% of his DNA that you didn’t get.

#2  DNA is not inherited in equal amounts from all ancestors

Since you know that you only got half of each of your parents’ DNA, it might now make sense to learn that you don’t share DNA with all of your ancestors.  Let’s just take your mother as an example.  You inherited 50% of her DNA, but the 50% that you got was basically “randomly” selected. 

You will, on average, share about 25% of your DNA with each of your mother’s parents, but it’s not really as simple as just “halving” DNA shared each generation.  It’s the randomness that gets us every time.

If you imagine that your mother shared less DNA than average with her paternal grandmother, for example, then your mother had less DNA for you to “randomly” inherit that matches this ancestor, so you might have either inherited all of your mother’s DNA that matched that great-grandmother, or only some of it. 

The more distant the ancestor, the more likely it is that you only inherited a small amount of DNA from them, and there is no way to figure out the exact percentage that you might have inherited (unless they are alive to do a DNA test to compare with yours).

The result is that your ethnicity estimate might show smaller or larger amounts of a particular ethnicity region than you were expecting to see.

# 3  You don’t share DNA with all of your ancestors

It might now seem obvious to you, but it’s important to note that because of the way that DNA is passed down, you won’t share DNA with every single ancestor that you have.  You don’t have enough room in your genome – it’s just not possible. 

That’s why we only get 50% of our parents’ DNA.  With each generation, some distant ancestors are “left out” of the DNA that is passed down.

From an ethnicity estimate perspective, this simply means that if you know that you had a great-great-great-great grandmother who immigrated from Spain to the United States, there is a chance that you didn’t inherited enough DNA from her to show up on an autosomal DNA test.  If you thought you would get Spanish DNA

#4  DNA testing companies often call the same regions by a different name, or group countries or regions together differently

What I mean by this is that some companies might group Ireland, Scotland, and Wales together into one group, and another company might report Ireland by itself, and a third company might lump Ireland, Scotland, Wales, and England into the same group.

Alternatively, one company might group all of North and South America into one group, usually Native American, and another company might divide this area into a few different regions. 

One great example is My Heritage, which groups Mexico into “Central America”, which might be really confusing, since we all know that Mexico is not part of Central America in a geographic sense.

This is why it is important to look at the map that comes along with the ethnicity results, since you might find that the part of the world that you expected to have on your results is actually included, just under a different heading or sub-heading.

#5  Political borders have shifted dramatically in many parts of the world over the past few hundred years

If you looked at my great-great grandfather’s entry in the US Census records in the early 1900s, you would think that he was Russian.  So why doesn’t my mother have more than 1% Russian DNA?  The main reason is because my great-great-grandfather wasn’t really Russian. 

He is Polish, and if you take a look at Polish history, you will see that Poland has been annexed by a few different countries in modern history.

Another great example from the United States:  A very sizeable amount of the United States previously belonged to Mexico, as many of us know.  The thing is, when this particular border changed, Mexico had only achieved Independence from Spain about 25 years prior to ceding territory to the United States. 

This means that some people with Ancestry from the US Southwest might say that they have “Spanish” ancestry, and others might say they have “Mexican” ancestry.  Genetically, however, their ancestry might look very similar, so someone from the part of the US that previously belonged to

People with ancestry from Mexico, which previously belonged to Spain, should take a look at the genetic makeup of people from Mexico to find out what to expect from an ethnicity estimate.

It is important to take a look at the history of the country where your ancestors were from and try to get a good understand of the ethnic makeup of that country.  This will help you know what to expect on your ethnicity estimate.

#6  You might not know as much about one line of your family as you do about another

This is another very common reason.  Sometimes we tend to focus on just one surname (typically, ahem, the paternal one), or the ancestors that we know the most about.  The thing is, we can inherit DNA from any ancestor, and sometimes we inherit DNA from ancestors that we don’t know anything about.

Growing up, I thought I knew a lot about my dad’s side of the family.  I knew that his mom had extensive US roots going back to Colonial times on many lines, and that his dad was Dutch.  When I really got working on my dad’s tree, I realized that I was missing a lot of information about his paternal grandmother. 

As it turns out, she was German.  I don’t know how I missed that growing up.  Even though German and Dutch usually shows up as Western Europe, it does explain the Eastern Europe that my dad got on his ethnicity estimate, which was also shared by his paternal uncle.

Basically, we can’t determine whether our ethnicity report is inaccurate unless we have done our homework first.  How can our ethnicity estimate line up with our tree when we don’t even have tree, or if it isn’t as complete as it could be?

Want to see how your ethnicity estimate compares to your family tree?

Conclusion

I hope that this post has given a little bit of balanced insight into why your ethnicity estimate usually won’t line up with what you know about your family’s ancestry.  If you have any questions, comment, or would just like to join the conversation about ethnicity estimate accuracy, I would love to hear from you below.

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