La Nouvelle République, March 2020. Article on the reliability of DNA testing. Click on the image to read the article in its entirety.

DNA testing, a genealogical tool

Called "recreational" by their opponents, mistakenly confused with medical tests, genetic genealogy tests open up new perspectives for genealogists. Practiced for 18 years in the United States and around the world, genetic genealogy tests enable people to discover their ethnic origins and find genetic cousins. This supplementary tool that genealogists have discovered can confirm a declarative family tree, complete it or partially disprove it.

Genetic data protected by the RGPD

When you entrust your saliva to one of the four major foreign laboratories performing these genetic genealogy tests, you are protected by the RGPD (European data protection regulations). If these tests were legalised in France, we would be assured that our authorities were verifying RGPD compliance and the terms of the contracts agreed with laboratories. However, these companies are vigilant about confidentiality issues, particularly in the United States. Indeed, their American users, the majority of whom use private health care, would risk a lot in the event of a sale of genetic data or a leak to health insurance companies or health mutuals. And those companies would risk extremely costly lawsuits for breach of contract.

The contract signed with the companies entrusts them with our DNA so that they can make a comparison with other users' data. Geneanet, one of the two major genealogy operators in France along with Filae, now offers this service free of charge with its beta test.

Ethnicity data that can be surprising

Using their reference panels, these laboratories will present a breakdown of your ethnic origins, with a different degree of precision depending on the laboratory: 42 geographical areas established by MyHeritage as opposed to 1,000 different areas for AncestryDNA. Many who take the test may be surprised how these results change over time. As the ethnicity reference panel improves, origins may differ. And as users, we have lifetime access to refined results.

Ignorance about this aspect of ethnic origins may lead to beginners judging that the results are unreliable. But it is nothing other than a question of variable quality of service, as with any commercial service: some are more efficient than others or improve over time in the face of competition. Users must inform themselves in the face of sometimes misleading advertising.

Genetic family tree

As a genealogist for more than 30 years, I was able to appreciate the unique ability of these tests to complete our genealogy, but also their limits. Let's go back to the genetic heritage of our ancestors present in our DNA. We have 23 pairs of chromosomes, exactly half of which are transmitted by the father and the other half by the mother. Each chromosome is a subtle assemblage of DNA segments inherited from each of our grandparents and great-grandparents. Each of us is a unique combination of the DNA of our ancestors up to the 6^th generation preceding us, ancestors born between 180 and 240 years before us. This inheritance can extend to a few 8^th generation ancestors, especially in endogamic populations.

In a genetic genealogy procedure, it's in our interests to have our older relations tested first, as their genetic links go further back than ours, allowing us to go back further into the genealogy and so uncover more ancestors and genetic cousins.

By comparing it with other DNA in the database, we will be able to find genetic cousins who, because they emigrated to another country, come from unknown branches of our tree. When moving to another country, our ancestors often used to change their surnames to help them integrate into their new homeland. But the DNA remains unchanged.

The genetic genealogy test turns out to be the only tool to identify an unknown, undeclared, natural father in our genealogy, or the biological family of an anonymously abandoned child, and so finally complete these cut branches.

Other genetic tests exist, such as the mitochondrial or Y chromosome tests, opening up other exciting prospects for genealogists. Historical riddles have been solved, such as the one concerning the children of the US President Thomas Jefferson, who was romantically involved with Sally Hemmings, a slave.

A new tool that is little known, overvalued or derided, genetic genealogy testing should be put back in its rightful place: a complementary tool for the genealogist, but a tool that is valuable, unique and sometimes indispensable.