DNA can tell us all kinds of things.
Genetic information can be used to uniquely identify a specific person using just a hair or a few drops of saliva. That data can also tell you if you have certain genetic ailments or are at an increased risk for others.
But one of the most common services provided by companies who do consumer DNA testing is an analysis of your “ancestry” based on your genetics, and there are real problems with that idea, geneticist Manolis Dermitzakis argued in a Reddit AMA question-and-answer session on November 17.
The University of Geneva genetics professor criticised attempts to pin down both “ancestral ethnicity” and “race” based on DNA.
That’s because these things are concepts or ideas that humans have created, and they don’t have a basis in genetics, according to Dermitzakis.
Genes can identify a person and find related people, but there’s no genetic meaning of race or even ancestry — just because DNA can say you are related to a large number of people who live in a place doesn’t mean you are genetically from that place.
‘Ancestry’ isn’t as definitive as we’d like to think
To tell people their ancestry, consumer DNA testing companies compare markers in customers’ genes to markers from other people around the world that are in their databases. They use those markers to give you as close an approximation to your “ancestry” as they can.
“I am always a bit worried about these companies,” said Dermitzakis. “What ancestry are we interested in? Based on current populations or ancient? Because it is easy to say that one is very similar to inhabitants of Greece today but much harder to say that they are similar to ancient Greeks.”
In other words, sure, you can say that the genetic markers in your database are similar to those of the people from a certain place that are now in the database of this genetic testing company. It doesn’t necessarily answer the more fundamental question that many have, which is “where am I from?”
Many scientists have criticised the idea of using genomic data to talk about ancestry.
“If a test-taker is just interested in finding out where there are some people in the world that share the same DNA as them, then these tests can certainly tell them that,” Deborah Bolnick, a geneticist and a co-author of an analysis on the topic told LiveScience in 2007. “But they’re not going to tell you every place or every group in the world where people share your DNA. Nor will they necessarily be able to tell you exactly where your ancestors lived or [what race or social group] they identified with.”
In 2013, the science education nonprofit Sense About Science released a public statement explaining why people shouldn’t use these tests to determine their ancestry.
“The results from your DNA tests could be matched with all sorts of different stories,” the statement read. “We don’t have to look back very far in time before we each have more ancestors than we have sections of DNA, and this means we have ancestors from whom we have inherited no DNA.”
“You cannot look at [an individual’s] DNA and read it like a book or a map of a journey,” the group concluded.
Genes don’t define ‘race’ either
By the same token, and perhaps more importantly, Dermitzakis dismissed the idea of using genetics to define “race.”
There’s a dark history of using genetics to talk about race. As Adam Rutherford (a former geneticist and now a writer) points out at The Guardian, one of the pioneers of the study of human genetics, Francis Galton, was also one of the creators of the eugenics movement. But since then, the study of genetics has exposed exactly why “race” is not a biological concept.
One Redditor asked Dermitzakis if the presence of certain genetic traits in certain parts of the world — traits that make fast-twitch muscle fibres common in a population in West Africa, or traits that made it easier for people in Nepal to adapt to high altitudes — defined “races” of people. The questioner wanted to know if there were racist implications in genetics that led to potential stereotyping of groups of people.
Dermitzakis said that trying to fit groups of people into “races” was biologically inaccurate in the first place.
“There are no races but individuals that sometimes are more related to each [other] than [to] others,” he said. “If you see it that way then all data will make more sense.”
The fact that certain characteristics exist in a certain area just means that those traits have been passed on frequently in that area. Because of those markers, genetic differences can be used to track the movements of populations around the globe, but there’s no one genetic signal that makes anyone a different race.
As population geneticist John Novembre explained it in a later Reddit AMA: “There simply hasn’t been enough time since we spread across the globe for extensive differences to have accumulated across the genome.”
Novembre says that “race to me, as I see it used in the world today and in US census categories, is something much more driven by historical legacy than biological understanding — it stems from a legacy based on judging a small number of external characteristics that hide the great amount of genetic similarity that exists under the surface.”
The great irony of genetics, Rutherford writes, is that it is the very field that disproved the beliefs of some of its racially-prejudiced early practitioners. Instead of showing how different we are, we’ve learned that from a biological standpoint, we’re 99.9% the same.
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