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August 30, 2022 – Almost everyone has played the Separated at Birth game and joked that lookalike friends and even celebrities who aren’t related could share a secret common ancestry.
But new research shows it’s no joke that there’s actually more to the idea of some doubles than meets the eye. A team of Spanish scientists studied pairs of unrelated doubles and found that they not only bear a striking resemblance to each other, but also share significant parts of their DNA.
The results published in the journal cell reports, suggest that these genetic similarities may go beyond mere appearance. DNA analysis based on the new work could one day help doctors identify a person’s hidden risks for certain diseases, and even help law enforcement officials target criminals through biometric forensics, the researchers say.
But perhaps most intriguing is the likelihood that most people on the planet have an unrelated “twin” out there somewhere. says Manel Esteller, PhD, a researcher at the Josep Carreras Leukemia Research Institute in Barcelona, who led the study.
“It’s not unreasonable to assume that you might have a doppelganger out there, too,” he says.
Eteller’s new study grew out of his research into the similarities and differences between identical twins. He was inspired by a photo project by a French-Canadian artist François Brunelle, who has been photographing unrelated doubles worldwide since 1999. His remarkable photographs prompted Esteller to ask: Could DNA explain these lookalike “twins”?
“In 2005 we discovered that twin brothers share the same DNA [also called monozygotic twins] epigenetic differences shown [chemical changes in DNA that regulate how genes are expressed] that explained why it wasn’t completely identical,” he explains.
“In the current study, we looked at the other side of the coin: people who have the same face but are not related to the family. These individuals helped answer the long-standing question of how our aspect is determined by nature and/or upbringing.”
To answer this question, Esteller’s team recruited 32 pairs of people from Brunelle’s photo sessions to conduct DNA testing and fill out lifestyle questionnaires. The researchers also used facial recognition software to assess their facial similarities based on headshots.
They found that 16 of the identical pairs had scores equivalent to true identical twins, which were also analyzed by the team’s facial recognition software. Of the matched pairs, 13 were of European descent, one Hispanic, one East Asian, and one Central South Asian.
The researchers then examined the DNA of these 16 pairs of look-alikes and found that they shared significantly more genetic material than the other 16 pairs, which the software considered less similar in appearance — a finding the researchers called “striking.”
Esteller notes that it seems “common sense” that people who look alike should share “important parts of the genome or DNA sequence,” but that has never been scientifically proven — at least until now.
“We found that the genetic loci shared by the doppelgangers fit four categories,” he says. “Genes previously reported to be associated with the shape and form of eyes, lips, mouth, nostrils, and other parts of the face that general population studies have used; genes involved in bone formation, which may relate to skull shape; genes involved in different skin textures; [and] Genes involved in fluid retention that can give our face different volumes.”
While the doubles’ DNA was very similar, Esteller was surprised to find that the lifestyle surveys – which assessed 68 variables – revealed large differences between the 16 pairs of people. These differences were almost certainly due to the environment and other parts of their lives and upbringing (think “diet vs. nature”) that had nothing to do with their genetic makeup.
Those differences, he explains, are another sign that the couples’ appearance similarities almost certainly have more to do with their shared DNA than anything else.
Still, he found that some doppelgangers were similar in ways that could be linked to their DNA — like height and weight, personality traits (like nicotine addiction), and even educational status (suggesting that intelligence might be linked to genes). ).
“They say our face reflects our soul,” Eteller says. “Since we’re less poetic, our doppelganger answered a large questionnaire to gather his physical and behavioral profiles. We have observed that lookalikes with high agreement in facial algorithms and genetic similarities share not only face but other traits as well. …”
So what explains these genetic similarities? Eteller says it is likely coincidence and coincidence, spurred by population growth and not the result of any previous, unknown ancestral or family connection. There are, he explains, just so many things that make up human facial features that it stands to reason that some people will—by coincidence—resemble others.
“As the human population is now 7.9 billion, these identical repeats are occurring more and more frequently,” he says. “Analysis of a larger cohort will provide more genetic variants shared by these particular individual pairs, and could also be useful in elucidating the contribution of other layers of biological data to determining our faces.”
Aside from the study’s odd scientific appeal, Esteller believes his findings could help diagnose diseases using DNA analysis. They might even one day help police hunt criminals — for example, by allowing forensic scientists to create sketches of suspects’ faces based only on DNA samples found at the crime scene.
“Two areas are now very exciting for further development,” he says. “First, can we use facial features to infer genetic mutations that are associated with a high risk of developing a disease like diabetes or Alzheimer’s? Second, can we now reconstruct a face from the genome that would be extremely useful in forensic science? Both research directions can now be pursued.”
Hear it from the doppelganger
Munzing, who has known Lee since her freshman year at UCLA 14 years ago, didn’t expect their DNA to be so closely matched.
“That definitely surprised me [we] might have similar DNA to having twins with my girlfriend,” she said in an email. “How crazy!! And cool! I call them my ‘twins’ from time to time, so I think it’s really fitting now!”
But knowing that we could all have a secret twin out there could help bring people together at a time when Americans and others around the world are so deeply divided along class, social and political lines, she says.
Lee agrees, noting that having a friend with a closely matched genetic profile “and even a similar face” contributes to a sense of connectedness with others we might see as strangers.
“It can be nice to feel like you’re not alone, even if it’s just because of your looks,” she says.
“We’re really more alike and connected than we think we are,” says Munzing.
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