• Researchers genetically compared humans who were identified by facial recognition algorithms as lookalikes.
• They analyzed their DNA sequences (genome), their DNA methylation statuses (epigenome), and their microbiome profiles.
• They found that 9 of these 16 non-blood-related lookalike pairs had very similar DNA, but differed in their epigenetic DNA methylation patterns and oral microbiome profiles.
• Interestingly, people with strong facial likeness also showed similarities in other physical features and personality traits.

All hereditary characteristics are encoded in distinct sequences of DNA, known as genes, which are transferred from parent to offspring. A person’s complete set of genes is referred to as their ‘genome’. According to the Human Genome Project, humans have between 20,000 and 25,000 genes.

In recent years, geneticists have found that genes can be switched on or off by chemical compounds and proteins that can attach to sections of DNA. These gene-regulating compounds and proteins are known as the “epigenome“.

In a study published in 2005, Dr. Manel Esteller, director of the Josep Carreras Leukaemia Research Institute, and his colleagues reported that identical (or monozygotic) twins share the same DNA but can exhibit differences in several traits, such as susceptibility to disease, due to epigenetic modification of their DNA sequence.

Now, a new study by Dr. Esteller and coworkers in the journal Cell Reports sheds light on the genome, epigenome, and microbiome profiles of people who have strong facial likeness but are not blood-related.

“The result is that these look-alike humans have similar genetic sequences and are therefore like twins, while their epigenetic and microorganism flora profiles differentiate them. Interesting[ly], not only do they have identical faces […] but by having similar DNAs they end up having [similarities in] other aspects of the body and similar personality traits as well!”
— Dr. Manel Esteller

“At its core, the study shows that there is a genetic basis of facial diversity. We already knew this because faces are heritable (i.e. you look more like your family than you do [other members] of the population) and other studies with random samples […] have been able to identify genetic variants in populations that are associated with facial features,” Dr. Michael Sheehan, associate professor of neurobiology and behavior at Cornell University, who was not involved in the study, told Medical News Today.

“This study takes that all to the logical extreme. If two individuals look really similar […], then that means that they will likely also share many genes identifying faces. Based on how we understand heritability and the genetic basis of traits, this outcome was expected,” he said.

Virtual twins and ultra-lookalikes

The researchers studied 32 pairs of humans identified as lookalikes by the French-Canadian photographer François Brunelle.

To ensure that their denomination as lookalikes was scientifically objective, the researchers ran photos of these pairs through three different facial recognition algorithms: one academic, one from Microsoft, and another from a security company. For half of the lookalike pairs (i.e. 16 out of 32), all three algorithms were unable to distinguish the faces, confirming that the pairs were objectively “virtual twins”.

The next step was to analyze molecular components that potentially influence the construction of the human face. For each study participant, the researchers determined the DNA sequence (genome), the DNA methylation status (epigenome), and the bacterial and viral content in oral swabs (oral microbiome).

The researchers found that 9 of these 16 lookalike pairs had very similar DNA, and labeled them “ultra-lookalikes”. All 9 ultra-lookalike pairs shared 3,730 genes. Most of the shared genes are known to be associated with human facial features, bone and skin properties, and liquid retention.

“The key to understanding this finding, I think, is to keep in mind that there is very limited genetic diversity in modern humans compared to our current population size. The human population has really exploded over the [10,000] years,” said Dr. Sheehan.

“The genetic diversity that determines traits like faces today is essentially the same genetic diversity that existed in the past. […] ultimately, all humans are sampling from relatively low levels of genetic diversity and so there are only so many combinations to go around. If you shuffle a deck of cards enough times you will find that you occasionally get the exact same card order.”
— Dr. Michael Sheehan

Among the 9 ultra-lookalike pairs, only one pair had similar DNA methylation patterns, and only one pair had a similar oral microbiome. This suggests that human lookalikes differ in their epigenome and microbiome.

Shared traits beyond facial features

Study participants also completed a comprehensive biometric and lifestyle questionnaire.

The researchers found that physical and personality traits—such as weight, height, smoking habits, and level of education —were correlated in lookalike pairs, implying that a shared genome not only relates to facial similarity but may also influence common habits and behavior.

The correlation between shared preferences and genome similarities is not a new idea.

“People who are friends tend to have some shared preferences, and studies have shown that friends are more similar genetically than you would expect by chance,” Dr. Sheehan told MNT.

Study limitations 

In their paper, the researchers acknowledge that the study is limited by its small sample size, which is “due to the difficulty to obtain look-alike data and biomaterial”.

Another limitation is that the study participants were mostly European, although the few studied Hispanic and Asian pairs showed the same results as the European pairs.

Dr. Sheehan told MNT that “we should expect roughly similar findings across other populations, though the exact details of the associated genes may vary from population to population.”

Studies have shown that African populations have higher levels of genetic diversity compared to non-African populations.

Real-world application

The findings of this study may open up new research avenues. The findings provide insights into the genetics of the human face and have potential future applications in various fields, such as biomedicine and forensics.

In the future, Dr. Esteller hopes it may be possible to infer from facial features “the presence of genetic mutations associated with a high risk of developing a disease such as diabetes or Alzheimer’s”.

Another potential application of these findings is in the field of forensic medicine, where it may be possible to reconstruct a criminal’s face from DNA.

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