Companies can analyze half a million SNPs or more in an ancestry test. When a genetic testing company gets a tube of your saliva in the mail, it first has to extract the DNA from it.
They make copies of your DNA, then break those stands up into shorter chunks. The chunks are then fed into a machine called a genotyping array. These arrays kind of — and this is an absolute simplification — work like a coin sorter, but for SNPs. Many SNPs are meaningless when it comes to our health. But they can be useful starting points for tracing ancestry. The more SNPs we share in common with another person, the more likely we share a similar, and more recent, ancestry.
Your ancestry is estimated by comparing your SNP results with a genetic database of people with known ancestries more on this in the next section. But even with that high level of accuracy, when you process 1 million places in the genome, you might get 1, errors.
Those small errors alone can help explain why one twin might have slightly different results from another. This source of error is why the health results you get back from genetic testing companies may show discrepancies too. Errors aside, the genotyping we get from each of the consumer testing companies should be just about identical to one another that is, if the companies are looking at the same set and number of SNPs.
But how companies analyze that raw data varies. Companies like 23andMe, Ancestry. The tests are looking for evidence that you have common ancestors with people in the reference group. But the reference group each company uses can be different. And the reference groups are changing all the time. As STAT news reports , people who used these tests just a few years ago are now finding their results have changed. Yet it also undercuts their marketing, which implies that their tests reveal something fundamental about you.
Another limitation: These reference groups are largely based on people who are self-reporting their ancestry. Prior to this past summer , 23andMe could only match people to just three broad regions in sub-Saharan Africa, which is an enormous area with a lot of geographic and ethnic diversity.
This is where computer programs come in. This also is imperfect, with a range of error. The computer programs are also sensitive to the small errors built into the genotyping process.
But your dad may not pass on to you all the genes he inherited from, for example, the Sardinian side of his family.
Of course not. DNA is not the same as heritage. What we call France has ballooned and shrunk over the centuries, overlapping at times with modern-day northern Italy. But in this update, we were able to split Italy into North and South. Using a sampling of reference panel members, whose ancestries they already knew, they ran their DNA through their algorithm to see if it would assign each person to the correct region.
They found their algorithm to be correct As a result, the DNA of indigenous people is often underrepresented in genetic databases, leading to results that can be misinterpreted. Ancestry gets around this by using DNA from admixed populations and identifying the segments that correspond to indigenous groups.
Ethnicity estimates also contain statistical noise, which is particularly relevant for those results in the low single-digit percentages. Still, some users treat these smidgens as meaningful. Or they might be a statistical mishap. Since you inherit roughly half of your DNA from each parent, half gets left behind. The sections you inherit are fairly random; you get a different alphabet soup than your non-identical twin siblings, for instance.
The area of the genome that Ancestry examines for place-based markers is separate from the genes affected by natural selection, like the ones that code for the taste receptors on your tongue. But certain marketing suggests otherwise. He takes a DNA test and discovers that— lo! Ancestry is not alone in pushing the message that DNA can unlock your hidden true self. Not so fast, say sociologists.
Although many people look to genetic ancestry for answers about where they belong, this line of inquiry risks infringing upon communities for whom those identities are central and important, says Alondra Nelson, president of the Social Science Research Council and author of The Social Life of DNA: Race, Reparations, and Reconciliation. What I find interesting is what people imagine these results tell them, and what people often do is resort to racial stereotypes.
Carl Linnaeus and Charles Darwin both racially classified people; Linnaeus erroneously assigned race-based personality traits. While mainstream scientists rejected eugenics and race science after World War II, those ideas persisted underground, in segregationist-funded, pseudoscientific journals like Mankind Quarterly, an anthropology journal first published in White nationalists subsequently invoked this research to support claims of genetic superiority.
Although legitimate studies of genetics consistently reaffirm that race is a social construct—albeit one with very real influence—the idea that we can biologically categorize people this way endures, even seeping into mainstream science in the form of studies and books advancing racist hypotheses.
This has played out during the pandemic through news of Black and brown people contracting and dying from Covid at disproportionately high rates. It was backed by men with giant armies, whose objectives were mass enslavement, conquest, and subjugation. In an ironic twist, however, race—and racism—have affected how we understand ancestry. While efforts have been made to produce more geographically representative samples , at-home DNA tests still give far more detailed answers about European ancestry than most other parts of the world.
All this leaves us with the question of how we should talk about race as genetic analysis becomes more commercialized and common. The results, no matter how personal, can have serious social ramifications.
That cynical use of biological data should make us deeply uncomfortable—and it should make us think further about the information that helps us define our own identities. Perseverance is having a blast collecting specimens on the Red Planet. Agricultural runoff isn't the only thing polluting waterways worldwide. Knee-deep in the rising tide, a Tuvalu minister's COP26 speech makes a big impression. Sign up to receive Popular Science's emails and get the highlights.
A Spanish-American family photographed in New Mexico in
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