People with similar faces share genetic similarities in DNA even if they are not related

Have you ever seen someone you thought you knew, only to find out that it was just someone who looked a lot alike? Many of us have seen double calling from loved ones, family members, and even ourselves. Now a study revealed that these doubles (doppelgängers ) not only look alike, but also likely have very similar DNA, and even share personality traits.

Researchers from the Josep Carreras Leukemia Research Institute in Barcelona revealed in an article published in the journal Cell Reports that the strong facial resemblance is associated with shared genetic variants.

The researchers wanted to answer the age-old question of whether we are “born” or “made”; that is, how much our genes “weigh” and how much upbringing is in how we end up being. That is why the doubles without family relationships were a huge clue to follow to shed light on this question.

“These results will have future implications in forensic medicine – reconstructing the face of the criminal from DNA – and in genetic diagnosis – the photo of the patient’s face already gives you clues about the genome he has -“, ​​said Dr. Manel Esteller, lead author of the study.

For decades, the existence of individuals who resemble each other without any family ties has been described as a proven fact, but anecdotal and without any scientific justification. However, the irruption of the Internet and social networks has caused thousands of personal photographs to be shared all over the world and has shown that the existence of “copies” between the faces of humans is more frequent than is believed.

In their new study, the team set out to characterize these random pairs who objectively share facial features, at the molecular level. The group of specialists recruited 32 look-alike couples who had been photographed by François Brunelle, a Canadian artist who has been photographing look-alikes since 1999.

The Spanish researchers used three different facial recognition algorithms to determine an objective measure of similarity of the couples. Participants also filled out lifestyle questionnaires and provided saliva samples for DNA analysis. “This unique set of samples allowed us to study how genomics, epigenomics, and microbiomics can contribute to human resemblance,” added Esteller.

The results revealed that the similar couples shared similar genetic compositions, or “genotypes.” However, they differed in DNA methylation (the regulation of gene expression) and in the landscapes of the microbiome (communities of bacteria, viruses, and fungi).

Physical traits, such as weight and height, and behavioral traits, such as smoking and education, were correlated among the lookalikes. This suggests that shared genetic variation is not only related to similar physical appearance but may also influence common behaviors and habits.

“Our study provides a rare insight into human similarity by showing that people with extremely similar faces share common genotypes, while being discordant at the level of the epigenome and the microbiome,” said the expert, who is also an ICREA research professor of Genetics at the University of Barcelona.

Although the researchers highlight several limitations of the study, such as the small sample size, the use of 2D black-and-white images, and the lack of diversity among the participants, they hope that the results may prove useful for future studies in the fields of biomedicine, evolution and even forensic medicine. Along these lines, Esteller concluded: “The final challenge would be to predict the structure of the human face based on the multi-omic landscape of the individual”.

The study comes shortly after researchers revealed that the chance of finding your doppelganger is one in a trillion. Teghan Lucas, a doctoral student at the University of Adelaide Medical School, conducted the study using a large database of facial and body measurements from almost 4,000 individuals, combined with mathematical equations, and found that using a combination of eight metric facial features, the probability of finding two faces with the same measurements in the general population was less than one in a trillion.

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