If this were simply about wearing kilts or liking Ed Sheeran, these ads could be dismissed as, well, ads. They’re just trying to sell stuff, shrug. But marketing campaigns for genetic-ancestry tests also tap into the idea that DNA is deterministic, that genetic differences are meaningful. They trade in the prestige of genomic science, making DNA out to be far more important in our cultural identities than it is, in order to sell more stuff.

First, the accuracy of these tests is unproven (as detailed here and here). But putting that aside, consider simply what it means to get a surprise result of, say, 15 percent German. If you speak no German, celebrate no German traditions, have never cooked German food, and know no Germans, what connection is there, really? Cultural identity is the sum total of all of these experiences. DNA alone does not supersede it.

Listening to 99 Luftballons or rooting for Germany in the World Cup is fairly trivial as these things go. But this wave of marketing campaigns encourages a way of thinking—that you can pick and choose which fractional parts of genetic identity to highlight when it makes for good cocktail-party conversation.

At a recent genetic-genealogy meeting I attended, an audience member asked how to convince people to upload their DNA results to more genealogy sites. “Tell them they’ll find they’re Native American and they’ll all go,” another person in the audience joked. The whole room laughed in recognition. Native American ancestry is an enduring fascination among Americans, and genetic-ancestry tests tap into an idea that something interesting, something unknown, might be buried in the past.

That’s the annoying version of conflating DNA and cultural identity. The even more insidious version is using genetic ancestry to game programs set up to address past injustices. As a demonstration of how that could be done, a man in Washington State cited a DNA test as evidence of his African (4 percent) and Native American (6 percent) ancestry.

When I previously spoke to Kim TallBear, a professor at the University of Alberta, about the case, she said it showed a grave misunderstanding of Native American identity. “It might be all these people have Native American ancestry,” she said. “My question is: Who cares?” Native American tribes usually require identifying relatives for membership. “If there’s a particular ancestor that is close enough you can find living family, then you can do that,” TallBear added. “If there’s nobody for you to find and no tribal community that’s going to claim you, it doesn’t really mean anything.” Nevertheless, she says, as genetic-ancestry tests have become popular, people have been showing up at tribal-enrollment offices with their results.

The most charged criticism against genetic-ancestry tests is that they emphasize people’s genetic differences, ultimately reifying race as a meaningful category when it is in fact a social construct. A 2014 study found that when people read a newspaper article about genetic-ancestry tests, their beliefs in racial differences increased. And white nationalists have taken to DNA ancestry tests to prove their European heritage.