In April 2018, we updated the Ancestry Composition Report to include new regions — your genetic groups — around the world. Genetic groups will provide you with information about your more recent ancestry, giving you insight into where your ancestors likely lived, and in some cases what ethnic groups they may have identified with or what languages they may have spoken.
Assigning Your Groups
Genetic groups (found within your Ancestry Composition results) are intended to complement your ancestral breakdown and provide a more recent and granular view of your ancestry. An assignment to a genetic group could reflect your connection to a recent ancestor or ancestors from a particular location (some genetic groups are based on geography), or it could mean you share a recent ancestor or ancestors with a group of people who belong to a particular ethnic group or speak a certain language (some genetic groups are based on a shared language or culture).
In order to be assigned a genetic group, you must share identical DNA segments with reference individuals of known ancestry from that group or location. Reference individuals for genetic groups populations for recent ancestor locations consist of over 400,000 customers, and this number will continue to grow as our customer database expands. Importantly, we don’t include close relatives (i.e. first cousins or closer) in this calculation, and these matching DNA segments must be unique, meaning we do not double-count identical segments you might share with multiple distant relatives. These initial steps determine the percent genome shared between you and the reference individuals for each group or location.
Next, we do a calibration step to set more meaningful thresholds that account for the special demographic histories of each group and location. This calibration step helps determine whether you share a similar genetic makeup to people who have recent ancestry from a specific group or location. We then use this comparison to set unique confidence thresholds for each genetic group.
Your genetic groups are not assigned to you as percentages. Instead, they are assigned at different confidence levels based on the number of individuals from that group with whom you share DNA. You can have a possible match to a genetic group, a likely match, or a highly likely match.
The strength of the match for each genetic group is determined by how much of your DNA you share with people from that group, calibrated by how many reference individuals there are. For a given genetic group, we indicate our confidence in the result. "Possible" means we are between 30% - 50% confident in the assignment, "likely" means we are between 50% – 80% confident, while "highly likely" means we are at least 80% confident in the assignment. "Not detected" means we are less than 30% confident in assigning that genetic group to you.
The map in your Ancestry Composition report is there to help you understand your ancestry percentages and genetic groups, and to see where those reference populations are located around the world.
In some cases, you may also see evidence of ancestry from more specific subregions, down to the state or even county level. The shaded subregions within each country or territory are where we have found evidence of your family’s recent ancestry. The stronger the evidence of ancestry, the darker the shading is for that region.
If you have a match to a group of people who say their ancestors spoke a certain language or belonged to a certain ethnic group, you will see a regional outline on your map that represents where their recent ancestors were born. Unlike your country matches, these outlines typically do not match political borders.
Keep in mind these outlines cannot show you where your ancestors lived with certainty. They can only reveal where your ancestors may have lived, because we use the ancestor birth locations reported by reference individuals as a proxy. This means that it is possible that the geographic locations of your shared ancestors may differ from the regions shown on the map. This may be due to major historical migrations and other events, which can result in initially surprising or unexpected results.
Why don’t I have any genetic group matches?
If you don’t share the minimum number of identical DNA segments with our reference individuals and/or the percent of your genome shared with our reference individuals does not pass our confidence thresholds, then you will not see any additional genetic groups or regions added to your Ancestry Composition Report. Keep in mind that Ancestry Composition can be considered a living analysis, so you may see genetic groups added in the future as new matches are detected or as new genetic groups are added.
A high percentage of my DNA is assigned to a particular ancestral population. Why don't I have high match strength with any of the associated genetic groups listed in my results?
To assign your genetic group matches, we look for identical pieces of DNA that you have in common with a large group of individuals with known ancestry from many regions worldwide.
The more DNA you share with reference individuals from specific genetic groups, the higher the likelihood is that those genetic groups will be assigned to you. However, you may not have enough DNA shared with reference individuals for us to assign that genetic group to you with confidence.
The likelihood that a genetic group will be assigned to you depends on other factors as well, including the region’s genetic history. For example:
- Matching a genetic group that’s based on geography: On average, people from a smaller, more homogenous country like Iceland will share more DNA with each other than people who come from a larger, more diverse country like China. As a result, it may be more difficult for us to identify ancestry from certain countries than from others, depending on their population history.
- Additionally, if you are from a group within a country that is not common in our reference dataset or is very genetically similar to other countries for which we have larger sample sizes, it is less likely that you will get a match you expect.
- Country borders have changed a lot even within the past 100 years, which can sometimes produce confusing results. For example, country borders in Eastern Europe and the Balkans changed dramatically with the dissolution of the Soviet Union in the last decade of the 20th century.
I have a parent genotyped. Do you know which side of my family a match to a genetic group came from?
No, while we can determine that a match exists to a genetic group, we don't know which copy of a chromosome (or, which side of your family) that match occurs on. This is because your phased chromosomes are not used to find matches.
Will you add more genetic groups over time?
Yes, we hope to add additional groups and regions in the future. You can consider your Ancestry Composition a living analysis, so your report may change over time. If new matches are detected or new locations are added, these will be added to your report.
Why did my genetic groups change?
The set of reference individuals we use to calculate your matches to genetic groups (the countries, territories, languages, or ethnic groups listed in addition to your ancestry percentages) are updated occasionally to include new reference individuals, so you may see your matches change as the size of our database grows. We are constantly working to improve this calculation in a way that is more precisely calibrated to each reference group.