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Ancestry Composition: Understanding Your Results

Explore the genetic ancestry you inherited from your ancestors—on both sides of your family—with your Ancestry Composition report. Your results reflect which populations your ancestors belonged to before the widespread migrations of the past several hundred years. While paper records might tell you the country an ancestor lived in, your genetics can tell you which regions of the world your DNA comes from—sometimes revealing previously unknown migrations or hidden ancestries. We recommend that you use your genetic reports together with your family history to build a complete understanding of your ancestry.

In this article, we’ll go over information that will help you explore your genetic ancestry using the Ancestry Composition report. At the end of the article, you can find some of the common questions we receive about this report, as well as links to more in-depth articles about how Ancestry Composition works and ways to further explore your genetic ancestry. For information about each section of the Ancestry Composition report, we recommend you visit our Highlights of Your Ancestry Composition Report article.

In this article, we will review the following topics:

Go to your Ancestry Composition report (opens in a new tab).

 

About Ancestry Composition

The Ancestry Composition report uses DNA you inherited from recent ancestors on both sides of your family and tells you the proportion of your DNA that comes from each of 31 worldwide populations, offering a detailed view of your genetic ancestry.

We believe Ancestry Composition set a new standard in the industry for rigor. In Quality Control tests, Ancestry Composition’s precision numbers were very high across the board, mostly above 90 percent. You can learn more in the Testing & Validation section of the Ancestry Composition Guide.

 

Tracing Your Ancestry

The results provided in the Ancestry Composition report reflect which populations your ancestors belonged to before the widespread migrations of the past several hundred years. Ancestry Composition reflects your autosomal DNA (chromosomes 1–22) and X chromosome DNA*.

It is important to remember that both men and women inherited autosomal DNA and X chromosome DNA. However, there are differences in the way these types of DNA are passed down from generation to generation.

  • Learn more about autosomal DNA
  • Learn more about the X chromosome
Autosomal DNA (Chromosomes 1–22)

Your autosomal DNA (chromosomes 1–22) is the DNA you received from all of your recent ancestors, on both sides of your family tree. This is the same for both men and women.

Who_passed_along_your_autosomal_DNA.png

X Chromosome

The number of copies of the X chromosome a person inherited depends on his or her genetic sex. Except in rare genetic conditions, women have two X chromosomes, one inherited from each parent; men have just one, inherited from their mother. Due to the way the X chromosome is passed down from generation to generation, there are fewer ancestors who could have contributed to the DNA on your X chromosome than to your autosomal chromosomes.

Male

The DNA on a male's X chromosome can only be traced to specific ancestors on his mother's side of the family. In the pedigree chart below, you can see which ancestors (from the past few generations) could have contributed to a male’s X chromosome.

Who_passed_along_your_X_chromosome_DNA_-_male_only.png

Note: To read the pedigree chart above, start with the blue square at the bottom of the chart (this represents you), and work your way through each generation to the top of the chart. Each ancestor is represented by either a circle or a square; female ancestors are represented by circles, and male ancestors are represented by squares. Ancestors that could have contributed to a male’s X chromosome are highlighted in blue.

 

Female

Women have two X chromosomes, one inherited from each parent. The DNA on each X chromosome can only be traced to specific ancestors. In the pedigree chart below, you can see which ancestors (from the past few generations) could have contributed to the X chromosome.

Who_passed_along_your_X_chromosome_DNA_-_female_only.png

Note: To read the pedigree chart above, start with the yellow circle at the bottom of the chart (this represents you), and work your way through each generation to the top of the chart. Each ancestor is represented by either a circle or a square; female ancestors are represented by circles, and male ancestors are represented by squares. Ancestors that could have contributed to the X chromosome are highlighted in yellow. Only the ancestors on your father’s side could have contributed to the copy of the X chromosome you inherited from your father. Likewise, only the ancestors on your mother’s side could have contributed to the copy of the X chromosome you inherited from your mother.

* The X chromosome is not currently used in the Ancestry Timeline section of this report.

 

About the Reference Populations

General Information | Broadly or Unassigned

General Information

The Ancestry Composition algorithm uses a total of 31 different reference populations to assign your genetic ancestry; there are 25 granular reference populations and 6 broader reference populations. The 25 granular reference populations are defined by genetically similar groups of people with known ancestry. When creating these reference populations, we attempted to define the population or geographic region represented by each dataset as small as possible. In some cases, we experimented with different groupings of country-level populations to find combinations that we could distinguish between.

The 6 broader reference populations, named “broadly” or “unassigned”, are combinations of the 25 granular populations. The Ancestry Composition algorithm starts by trying to assign your DNA to one of 25 granular populations. In the event the granular populations cannot be assigned at the selected level of confidence, the Ancestry Composition algorithm will attempt to assign the broader reference populations. You can learn more about this process in the Aggregation & Reporting section of our How Ancestry Composition Works article.

There are some genetic ancestries that are inherently difficult to tell apart, typically because the people in those regions mixed throughout history or have a shared history, or we might not have had enough data to tell them apart. As we obtain more data, populations will become easier to distinguish, and we will be able to report on more populations in the Ancestry Composition report.

Broadly or Unassigned Ancestry

Our Ancestry Composition algorithm looks at short pieces of your DNA one by one. For each piece, it calculates the probability that the piece belongs to each of the 25 different granular Ancestry Composition populations. When a piece doesn’t meet the minimum confidence level necessary to assign the DNA to a granular reference population, the algorithm will calculate the probability that the piece belongs to one of the 6 broader populations. These 6 broader reference populations are important because DNA markers vary widely in how strongly they are associated with a geographic location; some segments of your DNA may match reference data from many different places around the world. If a segment of your DNA matches reference DNA from several European countries but not from outside of Europe, then we label your DNA "Broadly European."

Some genetic populations are especially difficult to tell apart because they share a common history. If you have genetic ancestry from one of these populations—such as French & German—it may be assigned to a broader category. Broadly assigned ancestry tells a different story about your genetic history than narrowly assigned ancestry. Your DNA segments with broadly assigned ancestry match reference individuals from a relatively wide range of ancestry populations.

It is also possible to see a percentage of your DNA listed as “Unassigned.” There are two reasons why a piece of DNA might have unassigned ancestry:

  • The piece of DNA matches many different populations from around the world.
  • The piece of DNA does not match any of the reference populations very well.

We are proud of our state-of-the-art Ancestry Composition report, but we are also constantly working to improve our algorithm and our reference populations. As the science continues to get better, we will be able to report on and distinguish more Ancestry Composition populations. If you are interested in our populations and how the populations are selected, click here.

 

Exploring Your Ancestry Composition Results

The Ancestry Composition algorithm uses only the information in your DNA and the DNA of other people with known genetic ancestries (our reference datasets). If your results describe you perfectly, that just goes to show you how much your DNA really tells about you.

Sometimes, your results might not match what you expected based on historical record or family stories. There are a few common reasons why this might happen:

  • Some genetic populations are especially difficult to tell apart because they share a common history. If you have genetic ancestry from one of these populations, it may be assigned to a broader category. For example, Italian ancestry may be classified as a combination of Italian and Broadly Southern European.
  • Ancestry Composition populations are defined by genetically similar groups of people, not by the political borders of countries. In some cases, your ancestry may highlight the differences between population history and political history. For example, if you have ancestry from a part of France that is very close to the border with Spain, your DNA may be classified as Iberian (the population that includes Spanish ancestry) instead of French & German.
  • The time scale reflected by Ancestry Composition may be different from the time scale of your records. The reference datasets that we use to calculate your Ancestry Composition are designed to reflect distinct, genetically similar populations that existed before transcontinental travel and migration was common (at least 500 years ago). For example, if recent generations of your family lived in Latin America, you are likely to have some Native American and some Iberian genetic ancestry because most mixing between those two populations happened within the past 500 years.
  • In the case of Native American ancestry, you may have inherited little or no DNA directly from your Native American ancestors. The farther back in your history you look, the less likely you are to have inherited DNA directly from every single one of your ancestors. This means that you can be directly descended from a Native American without having any DNA evidence of that Native American ancestry.

Since genetics can tell which regions of the world a person’s DNA comes from, some people might learn about previously unknown migrations or ancestries. If you learned about a new, surprising or unexpected ancestry, there are a few ways you can further explore your genetic ancestry:

  • The Ancestry Timeline feature estimates how many generations ago you may have had a single ancestor who descended from a single population. Learn more.
  • The Chromosome Painting feature allows you to change the confidence level used to assign your ancestry, so you can be as conservative or speculative as you choose. If the ancestry is still assigned at a higher confidence level, it is more likely to reflect a real genetic history (and less likely to reflect random chance). Learn more.
  • Another way to gain confidence in your ancestry estimate is to connect with close relatives and see whether their results also include the same ancestry.

 

Common Questions

Why is my composition different than the composition for my sibling?

Unless you are an identical twin, you and your sibling received different segments of DNA from each of your parents. Siblings that share two parents, can expect to have only about 50% of their DNA in common. This means that 50% of your DNA is different than your sibling. These differences in the DNA you inherited from each parent can mean that you were assigned an ancestry that your sibling was not, or vice versa.

Why isn't an expected ancestry included in my composition?

There are a few common reasons why your Ancestry Composition might not match. One common reason is that some populations—such as our French & German reference population—that are difficult to assign because DNA associated with these populations is often associated with multiple regions. Instead of choosing arbitrarily from among these regions, the Ancestry Composition feature will label these type of segments as "Broadly" or "Unassigned.” Only DNA that meets or exceeds our confidence thresholds will be assigned to sub-regional population—such as French & German. Read more.

Learn more about Broadly Assigned and Unassigned ancestry.

Learn more about precision and recall in the Testing and Validation section of the Ancestry Composition Guide.

I received “broadly” or “unassigned”, does that mean you didn’t test me at those regions?

No, everyone is analyzed for every marker on our genotyping chip. The “broadly” and “unassigned” assignments mean we weren’t able to confidently assign the piece of DNA to a sub-population. Learn more in the Aggregation & Reporting section of the Ancestry Composition Guide.

What do small amounts (less than 1%) of ancestry mean?

Small amounts of ancestry can mean different things for different people, and you may have to do some digging to learn what the ancestry means for you:

  • You can learn more by looking at your Chromosome Painting. A small amount of ancestry is more likely to reflect a real genetic history (and less likely to reflect random chance) if it is still assigned at the higher confidence levels. Learn more.
  • Check out your Ancestry Timeline result for an estimate of when your most recent ancestor from each Ancestry Composition population lived, based on your genetics. Learn more.
  • Another way to gain confidence in your ancestry estimate is to connect with close relatives and see whether their results also include small amounts of the same ancestry.

 

Additional Resources

 

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