“Am I related to a Viking warrior?”

A few weeks ago Uppsala University’s Media Services received an e-mail from an American woman who had recently done a DNA test. Her test showed that she was related to a Viking warrior from Birka who turned out to be a woman, according to a 2017 genetic study. But is it really possible to find relatives in this way? We asked Mattias Jakobsson, Professor of Genetics at the Department of Organismal Biology, who uses historical DNA in his research on human evolution.

“This woman has probably done a mitochondrial DNA test that indicated she has the same mitochondrial haplogroup as the Viking woman. This means that she has the same, or very similar, genetic variation in the mitochondrion, which is a small organelle that exists in each of our cells and is passed on through heredity on the mother’s side. A common interpretation is that the individuals are related, but that is a premature conclusion. Many people have had the same specific mitochondrial variation a thousand years ago.”

Does this mean that the commercial genetic tests are not reliable?

“It depends on how the tests are designed. Mitochondria are just a part of our genetic makeup. Many modern tests look at large portions of the genome and provide much more information. They are really good at finding a sibling, cousin or near relative, for example, up to four, five steps or generations away. If you are interested in genealogy and immerse yourself into what the results show, it can be interesting, provided you do not just do a mitochondrial test. The test does not provide answers to where you come from, but it indicates individuals in the testing company’s database that you are a little more closely related to than other individuals. They might live in different parts of the world, but that does not mean your DNA originates there. DNA itself has no geographical origin.”

Is it also possible to get answers to what diseases you are predisposed to?

“If you have a serious test done, it may show what risk you have for contracting certain diseases. For example, the result may be that you have twice as much risk of Alzheimer’s disease above a certain age. But if the risk initially is, for example, 0.1 per cent, this would mean that twice as much risk is only 0.2 per cent. It is also important to know that the result refers to a specific gene. There may be 100 or 1,000 genes that affect a risk of disease, and a result indicating ‘twice as much risk’ refers to only the specific variation being examined.”

If we go back to our American questioner and female Viking warrior. How closely related would they be?

“If we say that there are about 1,000 years between them, this corresponds to about 40 generations. The human genome consists of about three billion base pairs. If we assume that they are related in a direct line of descent, then we halve the three billion for each generation. In that case the American and the Viking warrior woman would share less than one base pair of DNA as a result of a direct relationship.”