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Doppelgängers: yours is out there and you probably share DNA

That person who looks just like you is not your twin, but if scientists compared your genomes, they might find a lot in common, according to a study of doppelgängers that showed surprising results.

Charlie Chasen and Michael Malone met in Atlanta in 1997, when Malone was a guest singer in Chasen’s band. They quickly became friends, but they didn’t notice what other people around them did: the two men could pass for twins, reports The New York Times.

The two are doppelgängers. They look strikingly similar, but they are not related. Their immediate ancestors aren’t even from the same parts of the world; Chasen’s forebears hailed from Lithuania and Scotland, while Malone’s parents are from the Dominican Republic and the Bahamas.

The two friends, along with hundreds of other unrelated lookalikes, participated in a photography project by François Brunelle, a Canadian artist. The picture series, “I’m not a look-alike!” was inspired by Brunelle’s discovery of his own look-alike, the English actor Rowan Atkinson.

The project has been a hit on social media and the internet, but it’s also drawn the attention of scientists who study genetic relationships. Dr Manel Esteller, a researcher at the Josep Carreras Leukaemia Research Institute in Barcelona, Spain, had previously studied the physical differences between identical twins, and he wanted to examine the reverse: people who look alike but aren’t related. “What’s the explanation for these people?” he wondered.

In a study published in the journal Cell Reports, Esteller and his team recruited 32 pairs of lookalikes from Brunelle’s photographs to take DNA tests and complete questionnaires about their lifestyles. The researchers used facial recognition software to quantify the similarities between the faces.

Sixteen of those 32 pairs achieved similar overall scores to identical twins analysed by the same software. The researchers then compared the DNA of these 16 pairs of doppelgängers to see if their DNA was as similar as their faces.

Esteller found that the 16 pairs who were “true” lookalikes shared significantly more of their genes than the other 16 pairs that the software deemed less similar.

“These people really look alike because they share important parts of the genome, or the DNA sequence,” he said. That people who look more alike have more genes in common “would seem like common sense, but never had been shown”, he added.

However, DNA alone doesn’t tell the whole story of our makeup. Our lived experiences, and those of our ancestors, influence which of our genes are switched on or off – what scientists call our epigenomes. And our microbiome, our microscopic co-pilot, comprising bacteria, fungi and viruses, is further influenced by our environment.

Esteller found that while the doppelgängers’ genomes were similar, their epigenomes and microbiomes were different.

“Genetics put them together, and epigenetics and microbiome pulls them apart,” he said.

This discrepancy tells us that the pairs’ similar appearances have more to do with their DNA than with the environments in which they grew up. That surprised Esteller, who had expected to see a bigger environmental influence.

Because the doppelgängers’ appearances are more attributable to shared genes than shared life experiences, that means that, to some extent, their similarities are just the luck of the draw, spurred on by population growth. There are, after all, only so many ways to build a face.

“Now there are so many people in the world that the system is repeating itself,” Esteller said. It’s not unreasonable to assume that you, too, might have a look-alike out there.

He hopes the study’s findings will help doctors diagnose illness in the future – if people have similar enough genes to look alike, they might share predilections for diseases too.

“There seems to be something pretty strong in terms of genetics making two individuals who look alike also having genome-wide similar profiles,” said Olivier Elemento, director of the Englander Institute for Precision Medicine at Weill Cornell Medicine in New York, who was not involved with the study.

Discrepancies between DNA’s predictions and people’s actual appearances might alert doctors to problems, he said.

Esteller also suggested that there could be links between facial features and behavioural patterns, and that the study’s findings might one day aid forensic science by providing a glimpse of the faces of criminal suspects known only from DNA samples.

However, Daphne Martschenko, a postdoctoral researcher at the Stanford Center for Biomedical Ethics who was not involved with the study, urged caution in applying its findings to forensics.

“We’ve already seen plenty of examples of how existing facial algorithms have been used to reinforce existing racial bias in things like housing and job hiring and criminal profiling,” she said, adding that the study “raises a lot of important ethical considerations.”

Study details

Look-alike humans identified by facial recognition algorithms show genetic similarities

Ricky S. Joshi, Maria Rigau, Carlos A. García-Prieto, Xavier Binefa, Alfonso Valencia, Manel Esteller et al.

Published in Cell Reports on 23 August 2022

Highlights
• Facial recognition algorithms identify “look-alike” humans for multiomics studies
Intrapair lookalikes share common genetic sequences such as face trait variants
DNA methylation and microbiome profiles only contribute modestly to human likeness
• The identified SNPs impact physical and behavioural phenotypes beyond facial features

Summary
The human face is one of the most visible features of our unique identity as individuals. Interestingly, monozygotic twins share almost identical facial traits and the same DNA sequence but could exhibit differences in other biometrical parameters.

The expansion of the worldwide web and the possibility to exchange pictures of humans across the planet has increased the number of people identified online as virtual twins or doubles that are not family related. Herein, we have characterized in detail a set of “look-alike” humans, defined by facial recognition algorithms, for their multiomics landscape. We report that these individuals share similar genotypes and differ in their DNA methylation and microbiome landscape.

These results not only provide insights about the genetics that determine our face but also might have implications for the establishment of other human anthropometric properties and even personality characteristics.

 

Cell Reports article – Look-alike humans identified by facial recognition algorithms show genetic similarities (Open access)

 

New York Times article – Your doppelgänger is out there and you probably share DNA with them (Restricted access`)

 

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In a large Finnish study of twins, smoking is linked to bleeding in the brain

 

Environment plays ‘starring role’ in immunity

 

Common pain conditions share a genetic element

 

 

 

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