Credit: François Brunelle

People whose faces look very similar yet are apparently unrelated share genetic sequences as well as other physical attributes and behavior, an intriguing study indicates.

Close to 20,000 shared single nucleotide polymorphisms (SNPs) were identified among lookalikes, and these were associated not only with height and weight but also other characteristics such as smoking and education.

Nonetheless, the researchers note in the journal Cell Reports that the vast majority of lookalikes differed in their DNA methylation landscape and the microorganisms that naturally live in the body.

“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,” said researcher Manel Esteller, a professor of genetics at the University of Barcelona, Spain.

“Genomics clusters them together, and the rest sets them apart.”

He added: “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.”

The expansion of the worldwide web and the ability to exchange pictures of people across the globe has increased the number of people identified online as virtual twins.

For their study, the researchers recruited doppelgangers from the photographic work of François Brunelle, a Canadian artist who has collected worldwide pictures of lookalikes since 1999.

The team gathered headshot pictures of 32 lookalike pairs and used three separate facial recognition algorithms to objectively measure their likeness.

Participants completed a comprehensive biometric and lifestyle questionnaire and provided DNA samples in saliva.

Results showed that 16 of the 32 lookalike pairs were matched in all three types of facial recognition software used. Genomic analysis revealed that nine of these 16 pairs clustered together, based on 19,277 common SNPs for 3730 genes.

In addition, 68 biometric and lifestyle attributes studied in the pairs showed that physical and behavioral traits correlated in these individuals. This suggested shared genetic variation not only related to physical appearance might also influence common habits and behavior.

However, only one of the pairs clustered by DNA methylation. Similarly, only one pair clustered in microbiome analysis.

Overall, the researchers conclude: “These findings do not only provide clues about the genetic setting associated with our facial aspect, and probably other traits of our body and personality, but also highlight how much of what we are, and what defines us, is really inherited or instead is acquired during our lifetime.”

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