by In 2022 we reported on the DNA sequences of 33 medieval people in a Jewish cemetery in Germany. Shortly after we had made the data available publicly, people began to compare their own DNA with that of the German Jews from the 14th century and find many “games”. These medieval persons had shared DNA fragments with thousands of people who uploaded their DNA sequence to an online database, as well as they share DNA fragments with their relatives.
But what kind of relationship with a medieval person implies a common DNA fragment?
It turns out that it is not too much that helps research their family roots.
We are population geneticists who work with the old DNA. We understand how exciting it can be to find a genetic connection to certain people who have lived many generations ago. But these DNA agreements are not the narrow ties that you may imagine. That’s how it works.
Sequence of the DNA of those who lived a long time ago
The old DNA is a new and rapidly growing field with a Nobel Prize that will be awarded in 2022 for its basic work on Svante Pääbo.
Using samples from skull bones or teeth, DNA researchers can sequence the DNA of the people who lived back up to 100,000 years ago. More than 10,000 old DNA sequences or genome are currently available. These genomes, which come from all corners of the world, have dramatically revolutionized the understanding of the scientists from human origins.
A new trend in the old DNA is the sequencing of the genomes of “historical” individuals: those who lived in the past millennium.
Examples from Sweden, Norway, Denmark, Iceland, Poland, southeastern Europe and Londons, Cambridge and Norwich in Great Britain outside Europe have historical genomes from East Asia, the coast of Swahili, South Africa, the Canary Islands, Lebanon, Caribbean, Caribbean and Bay in Sanary. Genome enslaved Africans from Delaware, Maryland, South Carolina and St. Helena are also available.
Some historical genomes include named individuals, including Ludwig van Beethoven, the family of the last Russian tsar, medieval Hungarian royals, the Lakota Sioux leader Sitting Bull and King Richard III. From England.
How could you compare your own DNA with that of these historical people?
Several genetic tests for direct consumers such as 23Ande, Myheritage or Ancestry make reading their own genome sequence simple and affordable. You compare your DNA with that of your other customers. They identify relatives who share long and continuous DNA with them with them, and report to them to them – from the next to further away.
After the first consideration, 23Andme customers now have their genomes compare with historical people. Other genetic test companies don’t do it yet, but passionate genealogists can take the matter into their own hands. With the GedMatch service, users can, for example, upload their own DNA data together with the published DNA sequences of all historical people. After uploading, Gedmatch identifies every user with whom they share genetic material.
A comparison of the DNA sequence of a chromosome between a German Jew from the 14th century and two living people who uploaded their DNA to Gedmatch. Each thin vertical bar represents a letter in the DNA sequence and is color coded, based on whether it is a agreement. A common DNA fragment appears between the living person 1 and the medieval person. Gedmatch
What does a genetic agreement with a medieval person mean for your genealogy?
Surprisingly, very little.
Where genealogy and genetics distinguish
The first thing you should understand is how many ancestors you have in every past generation. A generation back, you have two ancestors. Two generations back, that doubles four. Then eight and 16. 30 generations around the 12th century, they have over a billion ancestors.
At this point, their ancestors clearly belong to most people from their population who lived at the time, except for a small fraction that did not leave long -term descendants. This includes remarkable people such as Charlemagne or Edward I., but also people in every medieval social class. Your family tree reaches each of these ancestors through numerous lines.
Mathematical research shows the following surprising fact. In a certain population, the number of lines in their family tree, which a certain medieval person reach, belongs between them and all others that belong to the same population they do. In other words, everyone who lives today is all genealogically related to all medieval people from this population.
The next step is to be understood how many ancestors you actually inherit DNA. Surprisingly, only very few.
Despite their millions or more medieval ancestors, they only inherit DNA from a tiny fraction of them. We are sorry, you probably didn’t inherit a DNA from Charlemagne or Edward I. For example, you only have about 2,000 genetic ancestors from the 12th century. In other words, their DNA sequence is a mosaic of approximately 2,000 “fragments”, each of which returns to a single person from the 12th century.
Who are the medieval people whose DNA has inherited you? Each fragment of her DNA increases from a random series of her family tree – the mother of the mother of the mother and so on – with every generation in the past and accidentally chooses one of two parents. The more lines in your family tree reach a certain medieval person, the more likely it is that you will inherit the DNA from this person.
However, remember that the number of family borders that a medieval person reach is approximately the same for all people from a certain population. Therefore, all individuals inherit the DNA from every medieval person with very similar probabilities. Share genetic material with one or the other medieval person is only a question of chance, and everyone plays the same game.
Here is an analogy. Going to a casino and rolling a roulette ball to 24 does not mean that 24 is your special number. Anyone else could also have rolled 24. Similarly, sharing a DNA fragment with someone from their millions of medieval genealogical ancestors does not mean a special relationship -apart from a DNA fragment.
And if you don’t have a common segment, you just had no luck. It does not mean that they are less genealogically related to this medieval person than everyone else from their population who has a common segment.
A “population” is not always well defined as a marginal note, but these arguments generally consider people with similar origins.
How to interpret a historical DNA match
Consider the medieval German Jews again. Some today’s Ashkenasian (European) Jews will share DNA with a certain medieval Jew. Some will share with another. Some will not share without any parts. It is a lottery. And since most Ashkenasian Jews are now very similar to the medieval German Jews, the common DNA fragment does not implant no unique genealogical relationship.
If you are ready to consider newer ancestors on the other hand, DNA games can be informative. The same mathematical models show that the number of family borders that a certain historical person reaches that lives about 200 or 300 years ago will vary in today’s people. Therefore, a DNA agreement with a person from the 18th century implies a more specific genealogical relationship that most other today’s Indviduals do not have.
This pattern was detected in a recent 23Andme study. 23Andme compares the genome of the enslaved Africans from the 18th century from Maryland with more than 9 million of their customers and discovered over 41,000 living relatives, including some almost direct descendants.
How far in time does a DNA match still have a genealogical meaning? Are the DNA agreement, for example, in the period between the late Middle Ages and the 17th century? We don’t know yet. Future research will be necessary to clarify this question and deviations from the simple model of a single, freely mixed population.
In the meantime, scientists who quickly accumulate historical genome sequences that bizarre behavior of human genealogies in the eye when interpreting a DNA match keep an eye on.
This article will be released from the conversation, a non -profit, independent news organization that brings you facts and trustworthy analyzes to help you understand our complex world. It was written by: Shai Carmi, Hebrew University of Jerusalem and Harald Ringbauer, Max Planck Institute for Evolutionary Anthropology
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Shai Carmi is a paid consultant and holds stock options at myheritage.
Harald Ringbauer does not work for a company or an organization that benefits from this article and have not published any relevant affiliations about their academic appointment.
