It is possible that a family member or friend has told you that they have met a ‘double’ of yours. Or perhaps the ‘fright’ has been greater if it has been you yourself who have found your ‘twin‘ down the street, recognizing in him the aquiline nose that he shares with his mother, the slanted eyes that he inherited from his father and even the hole in his chin that his grandfather also has. Or perhaps, because of the theory that says that we all have a double somewhere in the world, he has tried his luck with an application or internet page. Well, he must know that, if he has found a ‘copy’ with the same face as his, this person will share much more than a few features: he may have much of his ADN -although they live on different continents- and even behaviors and habits, such as smoking or the type of education, will be similar.
This is the conclusion of the study recently published in the journal ‘Cell Press’ and carried out by a team from the Josep Carreras Leukemia Research Institute (IJC), led by Manel Esteller, who is also ICREA Research Professor and Professor of Genetics at the University of Barcelona. “In 2005 we discovered that twin brothers who had the same DNA (also called monozygotic twins) had epigenetic differences (chemical modifications in the DNA sequence that regulate gene expression) that explained why they were not perfectly identical”, the authors explain. “In this study we have explored the other side of the coin: people who have the same face, but who are not related.”
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 our upbringing weighs on how we end up being. That is why the doubles without family relationship were a huge vein to shed light on this issue.
an amazing resemblance
The researchers recruited 32 look-alike couples who had been photographed as part of a series by the Canadian artist. Francois Brunelle, who has been traveling the world for years to find these ‘twins’ without any family relationship and whose work has promoted other similar scientific studies. To check that their features were similar, the team used three different facial recognition programs. The results showed a very high degree of similarity: 25 of the 32 pairs (75%) were considered ‘twins’. “This is very close to the human ability to recognize identical twins,” says Esteller. However, only 16 couples who were recognized by all three programs entered the experiment.
These 32 people were genetically profiled to detect common genetic variations. And they looked further: their epigenetic profiles (mechanisms that regulate how DNA is manifested, but without changing it) and their microbiome (the set of bacteria and viruses that inhabit a given human body) were also analyzed. The couples also completed a biometric questionnaire – a short test to assess a person’s level of risk of contracting certain diseases and medical conditions – and a lifestyle questionnaire – with questions such as whether they smoked or drank alcohol.
The results revealed that the genes shared by the couples corresponded to five categories: on the one hand, genes known to be associated with the shape of the eyes, lips, mouth, nostrils and other parts of the face; genes involved in bone formation, which may be related to the shape of the skull; genes involved in different textures of the skin; genes related to fluid retention, which can give different volumes to our face; and, finally, to genes of unknown function that, however, are related to the face properties.
Furthermore, among these 16 pairs, many were similar in weight and height, and analysis of their biometric and lifestyle factors also showed that there were similarities. In fact, behavioral traits such as smoking and level of education were correlated among similar pairs, suggesting that shared genetic variation is related not only to physical appearance, but may also influence common habits and behavior. .
Applications in biomedicine or forensic science
“Our findings provide a molecular basis for future applications in fields such as biomedicine, evolution, and forensic science,” explains Esteller. For example, it could be used in forensic medicine to create a system from which the face of a criminal (or an unidentified victim) could be reconstructed from her DNA. “And in medicine, we could deduce a person’s genome from facial analysis and thus use it as a screening tool to detect the presence of disease-associated genetic mutations and apply preventive strategies at an early stage,” he says. .
Although the study had a small sample, according to the authors “it has the correct statistical power”, so they hope that the results will not change even if the group is expanded. “Because the human population is now 7.9 billion people, it is becoming more and more likely that these similar repetitions will occur. Analysis of a larger cohort will provide more genetic variants shared by these special individual pairs, and could also be useful in elucidating the contribution of other layers of biological data in determining our faces,” Esteller concludes.