Lookalikes share DNA and personality traits, says study

In 1999, François Brunelle, a Canadian artist, and photographer, began documenting look-alikes in a picture series "I'm not a look-alike!", inspired by his discovery of his look-alike, the English actor Rowan Atkinson.

The project, undoubtedly, was a massive hit on social media and other parts of the internet, but it also drew the attention of scientists who study genetic relationships.

Particularly Manel Esteller of the Josep Carreras Leukaemia Research Institute in Barcelona, Spain.

According to The New York Times, Esteller 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.

Esteller and his team set out to characterize, on a molecular level, strangers that objectively share facial features. And to do so, they recruited human doubles from Brunelle's photographic work. The team obtained headshot pictures of 32 lookalike couples and determined an objective measure of likeness for the pairs using three different facial recognition algorithms.

"Our study provides a rare insight into human likeness by showing that people with extreme lookalike faces share common genotypes, whereas they are discordant at the epigenome and microbiome levels. Genomics clusters them together, and the rest sets them apart," Esteller said in a statement.

The work was published in the journal Cell Reports.

Genetics put them together

The participants also completed a comprehensive biometric and lifestyle questionnaire and provided saliva DNA for multiomics analysis. "This unique set of samples has allowed us to study how genomics, epigenomics, and microbiomics can contribute to human resemblance," Esteller said.

Overall, the results revealed that these individuals share similar genotypes, but differ in their DNA methylation and microbiome landscapes. All three algorithms clustered half of the lookalike pairs together. Genetic analysis revealed that nine of these 16 pairs clustered together, based on 19,277 common single-nucleotide polymorphisms.

"These people really look alike because they share important parts of the genome or the DNA sequence," Esteller told The New York Times. That people who look more alike have more genes in common "would seem like common sense, but never had been shown," he added.

Physical traits such as weight and height, and behavioral traits such as smoking and education, were correlated in lookalike pairs. Altogether, the results suggest that "shared genetic variation not only relates to similar physical appearance but may also influence common habits and behavior".

The study could someday aid forensic science

"We provided a unique insight into the molecular characteristics that potentially influence the construction of the human face," Esteller said. "We suggest that these same determinants correlate with both physical and behavioral attributes that constitute human beings."

Small sample size, the use of 2D black-and-white images, and the fact that the majority of the cohort included European participants were a few study limitations. Despite these, the findings may provide a molecular basis for future applications in various fields such as biomedicine, evolution, and forensics.

"These results will have future implications in forensic medicine—reconstructing the criminal's face from DNA—and in genetic diagnosis—the photo of the patient's face will already give you clues as to which genome he or she has," said Esteller. "Through collaborative efforts, the ultimate challenge would be to predict the human face structure based on the individual’s multiomics landscape."

Study 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 world wide 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 into the genetics that determine our face but also might have implications for the establishment of other human anthropometric properties and even personality characteristics.