Historical Matches FAQ

What does it mean to have a historical match?

• You share one or more identical segments of DNA with each of your historical matches. In order for two people to share an identical segment of DNA, they must have inherited it from a shared ancestor at some point in the past. The longer the DNA segment you share (and the more segments you share), the more recently your shared ancestor likely lived. In most cases, this shared ancestor lived hundreds, if not thousands of years before either you or your historical match. 

Am I directly descended from the historical individual(s) I share a match with?

• Probably not! Or at least not in the way you might think. The vast majority of genetic matches that 23andMe identifies do not provide evidence that you are a direct descendant of the historical individual whose genome we have analyzed. Instead, both you and the historical individual you share a match with likely inherited this shared segment of DNA from a common ancestor who lived many generations before either of you.
• In most cases, even if you are directly descended from one or more of the historical individuals you share a match with, we wouldn’t be able to tell this based on the DNA that you share with them. This is because as you trace your pedigree back in time generation by generation you start to have so many genealogical ancestors that the amount of DNA that you inherit from each of your ancestors is tiny. In fact, after about 8 generations or so (when you have 256 6th-great-grandparents from that generation alone), you start to have genealogical ancestors that you don’t inherit any DNA from directly. And as you go even further back in time, the fraction of your genealogical ancestors that you don’t inherit any DNA from increases. For instance, if you trace your ancestry back 15 generations, you likely only inherited DNA from about 3% of your genealogical ancestors.
• At this point, it becomes almost impossible to determine whether you share DNA with a historical individual because you are their direct descendant and they passed that specific segment of DNA on to you or because you both just happen to have inherited that same piece of DNA from another shared ancestor who lived long before either of you. So what we can say with a high degree of confidence is that you and that historical individual share a common ancestor, and that you and that historical individual inherited some of the same DNA from that common ancestor.
• However, there is an exception to this. If the historical individual that you share a match with lived within the last few hundred years AND you happen to have inherited a very large amount of DNA from them—the exact amount of DNA will vary depending on their ancestry and other factors, but is typically at least 30 cM—we may be able to tell that you are either a direct descendant of this historical individual or a direct descendant of one of their very close relatives (i.e., their sibling or cousin). If we believe that a historical individual you share a match with could be your direct ancestor (or a very close relative of your direct ancestor) based on your DNA we will tell you. You can find this information in the “Your Genetic Relationship” section of the historical match profile page, where your “predicted relationship” would be listed as “significantly related.”

You told me that I am “significantly related” to one of my historical matches. What does that mean?

• That’s exciting! If your predicted relationship to one of your historical matches is listed as “significantly related” this means that your DNA indicates that you likely share a common ancestor in the recent past. In most cases*, we cannot tell from DNA alone whether you may be a direct descendant of this historical match or if your shared common ancestors lived several generations before the historical individual we compared you to (meaning that you might descend from one of their siblings or cousins).
• Most of the historical matches that we identify only involve a small number of relatively short shared DNA segments, and therefore likely represent a shared common ancestor who lived hundreds or thousands of years ago. Due to the random way in which DNA is inherited, it is difficult to determine exactly when that shared ancestor may have lived. However, matches that are classified as “significantly related” share enough DNA that we can be confident that you shared an ancestor relatively recently in time.
• While we can’t tell from your DNA alone exactly how you are related to the historical individual that you share a “significant relationship” with, we hope that this information might inspire you to explore your family history further using a genealogical approach.
• Historical matches that are classified as “significantly related” are quite rare and 23andMe is always excited to hear about them. If you received a “significantly related” match and you have a story that you’d like to share with us, please submit your story at 23andme.com/stories.
• *In some cases, we can be sure that you are NOT a direct descendant of your historical match, but instead that you are descended from one of their close relatives. For instance, if your historical match died as an infant, you cannot be their direct descendant. Be sure to read the description of the historical individual you match with to see if this is the case.

How confident are you in these matches?

• We only report matches to historical individuals if we are confident that you share identical segments of DNA with them. We use an approach that was developed and rigorously tested by population geneticists at 23andMe in collaboration with leading researchers in the field of ancient DNA. The approach was fully described in an academic publication which underwent peer review by experts in the field and was published in the journal Science (PDF access here).
• In order to ensure that we only report matches that we are confident in, we consider two major factors:
• First we consider the quality of each historical individual’s genome. Specifically, we consider the proportion of missing DNA data (i.e. the positions in their genome for which we were able to determine a genotype vs those that we were not). Genomes with very little missing data are considered to be high quality, while those with more missing data are considered to be lower quality.
• We also consider the length of the DNA segments that you share with each historical individual (measured in centiMorgans, or “cM”). The longer the segment of DNA that you share with that historical individual, the more confidence we have in your match.
• Considering these two factors together, this means that for high quality historical genomes that have very little missing data, we can confidently report matches to historical individuals that you share segments of DNA with that are as short as 3 cM. Whereas for lower quality genomes we use a 9 cM minimum threshold. We do not report matches to historical individuals with more than 25% missing data at this time, as we have less confidence that any shared segments of DNA that we may identify are real. 

Why don’t I have any historical matches?

• We have compared your DNA to the DNA of a variety of historical individuals from across the globe whose genomes have been sequenced. Although you do not share a genetic match to any of the individuals who are included in the feature at this time, this may change as we add more historical individuals and as we make improvements to the algorithms that we use to detect your historical matches.
• The approach that we use to detect your historical matches is conservative, meaning that we only report a genetic match if we are confident that it is authentic. How confident we can be in a genetic match depends on BOTH the quality of the DNA that (non-23andMe) researchers were able to generate from the historical individual AND the length of the DNA segment that you share with that historical individual. For the best quality historical DNA (typically this means it has the least missing genetic information) we are able to detect shared DNA segments that are as short as 4 cM. But for the lowest quality historical DNA samples included in this feature, we only report shared DNA segments that are longer than 9 cM. It is therefore possible that you share real segments of DNA with historical individuals that are too short for us to confidently detect at this time.
• 23andMe scientists are working to add more profiles of historical individuals whose genomes have been sequenced as they are made available by researchers around the world, so check back in to see if you have a new historical match.
  
  

What does it mean to have a historical match from a different part of the world from you?

• It is possible to share DNA with a historical individual who is from a different part of the world from you. This can occur because human populations have traveled great distances throughout history and prehistory, so you may share DNA with a historical individual who was closely related to a population that later migrated to a part of the world from which you have known ancestry. For example, if you have known European ancestry, it’s very possible you may discover a historical match whose remains were discovered in Central or South Asia, due to shared relatives who lived in the Eurasian Steppe during the Bronze Age or earlier. Similarly, you might find out that you are distantly related to a Viking even if you don’t have any European ancestry. If that’s the case, you are likely connected via a shared ancestor who lived in the Steppe thousands of years ago.
• Fun fact: it’s estimated that a common ancestor of every human alive today could have lived as recently as 5,000 years ago (note: this would be the most recent common ancestor of everyone alive today, not the first or only common ancestor of everyone alive today).

Why does this feature include more historical individuals from Europe than in other parts of the world?

• Although we aim to include historical individuals from around the world in this feature, significantly more historical genomes have been sequenced from Europe and elsewhere in Western Eurasia than anywhere else on the globe to date. There are a few reasons why there are more historical genomes available from this part of the world than others.
• First, a primary reason for this bias is that many of the largest ancient DNA labs in the world, who are responsible for generating this data, are located in Europe. Therefore, many of the research questions that they have chosen to focus on—particularly in the earliest days of the field of ancient DNA—have involved European archaeological sites. Another reason is that certain climate conditions are more favorable to the preservation of DNA over long periods of time. Humidity, heat, and acidic soil conditions damage DNA much more quickly than dry climates, cold temperatures, and neutral or basic soil conditions. Many warm, humid regions, such as rainforests or the tropics, are not well suited to the long-term preservation of DNA (though some DNA in these regions remains stable for far longer if preserved deep inside a cave). Conversely, DNA can remain stable for much longer in cool, dry locations with low soil acidity, and on average there are more regions with these conditions in the global North. 
• Over time, researchers are developing better techniques that allow them to recover and analyze more DNA from the remains of individuals in warmer, humid climates and many ancient DNA labs have been established outside of Europe (and European researchers are also tackling questions about ancient individuals from outside of Europe). So we expect that this geographic bias will change in the future. But for now, there are still many more historical genomes available from Europe than elsewhere.

How does 23andMe get the DNA of these historical or ancient individuals?

• 23andMe scientists work only with publicly available ancient DNA data, which is made available by researchers around the world who are studying historical and ancient individuals.

Will more historical individuals be added in the future?

• Yes. As more historical genomes are published and made publicly available, we will continue expanding the number of reference individuals in the Historical Matches feature, which is available to active 23andMe+ Premium and Total Health members.

Can 23andMe analyze my known ancestor’s remains?

• No, 23andMe does not (and cannot) accommodate requests to analyze DNA from your ancestor’s remains.

I share X% of my genome with one of my historical matches. How many generations ago did our shared common ancestor live?

• In the vast majority of cases, we cannot directly estimate how many generations ago you and your historical match shared a common ancestor.
• This is because you inherit (almost) exactly 50% of your DNA from each parent, but the amounts of DNA you inherit from each previous generation of ancestors can vary widely, until you reach a point where—by the random luck of genetic recombination—you inherited no DNA from one or more of your direct ancestors and DNA segments of varying sizes from others. For example, you inherit 25% of your DNA on average from each of your four grandparents, but you can inherit as little as 20% from one grandparent and as much as 30% from another. Going a little further back in time, there is a 5% chance that you inherited zero DNA from a 5th-great-grandparent. But the “random chance” of genetic recombination and inheritance also means that it’s possible to have inherited a small percentage of your DNA from a very distant ancestor, i.e. somebody who was your 40th-great-grandparent.
• Additionally, just because you share DNA with a historical individual does not mean you are directly descended from them. That historical DNA match may have died when they were too young to have children, or your historical DNA match may have had children, but those children did not reproduce, or their children did not reproduce. Or maybe they did, but you are not one of their descendants. Instead your direct ancestor might have been the first cousin or the 5th cousin of your historical match.
• So while we can’t pinpoint your exact relationship using DNA alone in most cases, what we can say with a high degree of confidence is that you and that historical individual share a common ancestor who lived at some point in the past, and that you and that historical individual inherited some of the same DNA from that common ancestor. 

Is there a difference between “historical” and “ancient” DNA?

• The term “ancient DNA” can be used to refer to DNA that has been extracted from humans (and other organisms) who lived as recently as 100 years ago or as many as 1 million years ago. This is because the term really refers to the set of techniques that researchers use to extract DNA that has degraded over time from the remains of individuals who lived long ago, rather than to the actual age of the individual. Regardless of whether an individual died just a few hundred years ago or ten thousand years ago, researchers use similar techniques to extract their DNA. All of these techniques were developed as part of the field of ancient DNA.
• Since more and more studies are starting to apply ancient DNA techniques to the remains of individuals who would typically be classified as “historical” rather than “ancient,” some people are starting to use the term “historical DNA” as well. But the two terms are typically interchangeable.

Why do you use random letter/number codes to refer to the historical individuals? Wouldn’t it be more personalized if you gave them names?

• Except in very special circumstances, historians and anthropologists typically avoid making up names for the historical individuals that they study. This is out of respect for the fact that these are real people who had names. Although those names may now be lost to time, they should not be overwritten. We therefore follow this convention and do not assign new names to the historical individuals that we feature.
• The codes that we use to refer to each historical individual match those that were used when the historical individual’s DNA was published. So if you want to learn more about a particular historical individual, you can look them up using these IDs.

Why aren’t you showing photographs of the skeletons? Where can I find them?

• While photographs of the skeletal remains of many of the historical individuals highlighted in this feature are available elsewhere, we do not show these photographs out of consideration for customers and others who may find them upsetting or disrespectful.
• There are a diversity of cultural traditions and personally held opinions that define if and when it may be appropriate to take and display photographs of deceased humans. Human remains are actively displayed as part of many religious and cultural traditions, while viewing them is considered taboo in others.
• In some cases, images of the skeletal remains of the historical individuals included in this feature are available online, including in the supplementary materials of the academic journal articles in which they were first described (which are linked in the references section on each “group” page), in news articles, or in museum archives.

Why do you keep referring to the “genetic sex” or the “morphological sex” of the historical individuals, rather than just to their sex or gender? And why do you use gendered language and imagery to refer to the historical individuals when you don’t know how they identified?

• Researchers use a variety of approaches to estimate the sex of historical individuals based on their skeletal remains alone. The two most common approaches are based on the individual's skeletal morphology—through examination of bones that tend to differ between the two sexes, including the pelvis—and their genetics, often by determining whether or not they had a Y chromosome (although there are other genetic factors that also contribute to genetic sex).
• Both of these approaches are imprecise and we highlight many instances throughout this feature where researchers come to different conclusions about a historical individual’s morphological and genetic sex. We therefore are careful to indicate the approach that was used to estimate each historical individual’s sex.
• Determining a historical individual's gender is even more complicated. Often historical individuals are buried with artifacts that were associated with a particular gender in the society in which they lived, giving us some clues about how they may have personally identified or been identified by others. However, there is no way to determine this with certainty, particularly in cases where there is no written record of their life.
• We use gendered language and imagery throughout the feature which is determined based on the genetic sex of the historical individual, except in cases where there was archaeological evidence to suggest that the individual’s gender expression may have differed from their genetic sex. We acknowledge that it is an oversimplification of the complex relationship between sex and gender.
  
  

Why don’t my Historical Matches results match the results I got from a different company?

• While we are very confident in the way we calculate your results, we cannot make statements about the quality of your results from a different company. But if your results from 23andMe don't match the results you got from a different test, that could reflect differences in the types of historical matches being reported and the algorithms used to identify them.
• When you compare your Historical Matches to results that you received from another company, there are a few things that you should keep in mind. First, make sure that the type of connection reported by each company is the same. Similar to our DNA Relatives feature, the 23andMe Historical Matches feature searches for portions of your genome that are identical to the historical individuals we are comparing you to. You share at least one identical stretch of DNA with each of your historical matches, and this means that you both inherited that piece of DNA from a shared common ancestor at some point in the past. This is evidence of a direct connection between you and the historical individual that you match with, although it may be via a shared common ancestor who lived hundreds or thousands of years ago.
• There are other ways that you could be genetically connected to a historical individual. For instance, some companies may consider a historical individual’s maternal or paternal haplogroups. If you share the same maternal haplogroup as a historical individual, this means that at some point in time (possibly thousands of years ago) you share an ancestor in your maternal lineage (i.e. via your mother’s, mother’s mother, etc). While if you share the same paternal lineage, this means at some point in time, you share an ancestor on your paternal lineage (i.e. via your father’s, father’s father, etc). Often, shared haplogroups reflect a very distant connection to a shared ancestor who lived thousands of years ago. Currently, the 23andMe Historical Matches feature does not report shared maternal or paternal haplogroups.
• It is also possible to calculate a similarity score that highlights how similar your genome is to various historical groups or people, relative to a set of reference populations. In this case, a high similarity score is not an indication of a direct genetic connection, but is instead an indication of shared ancestry. Some companies may calculate a similarity score that compares how similar your ancestry is to one or more historical individuals, however this is different from the type of match that we report in the 23andMe Historical Matches feature.
• When in doubt, be sure to consider whether the algorithms used to calculate your results have been optimized to work on DNA from historical and ancient individuals. The approach that 23andMe uses to identify historical matches was developed by researchers at 23andMe in collaboration with experts in the field of ancient DNA. It also underwent peer review by experts in the field before being fully described in a publication that appeared in the leading journal, Science (PDF access here).