New research reveals common features o


image: Four pairs of ‘lookalike’ humans, included in the study, showing similarities in their DNA. Photographer, François Brunelle.
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Credit: François Brunelle

Barcelona, ​​August 23, 2022. The question of the role of nature vs. nurture in the development of human beings is still far from being resolved. Although some of the questions have been answered by twin studies, in the case of unrelated individuals, researchers must passively wait for the correct model to emerge. Now, for the first time, researchers have been able to study pairs of unrelated people who look alike and determine the impact of inheritance in relation to the environment.

In an article published today in Cell Reports*a team led by Dr. Manel Esteller, director of the Josep Carreras Leukemia Research Institute, research professor at ICREA and professor of genetics at the University of Barcelona, ​​presents the results of a study that clearly shows that these “doppelgängers” (doubles) have similarities not only in their facial appearance, height, weight, etc., but also in certain aspects of their behavior.

“For decades, the existence of individuals who look alike without having family ties has been described as a proven fact, but only anecdotally and without any scientific justification”, explains Dr Esteller, and adds that “the Widespread use of the Internet and social networks for sharing images have allowed us to identify and study these people.

The researchers recruited 32 look-alike couples who had been photographed as part of a series by Canadian artist François Brunelle. All participants completed a comprehensive lifestyle and biometrics questionnaire in their native language. Three different facial recognition programs were then used to determine how “similar” each pair was. The number of couples considered to be correlated by at least two programs was very high (75%, out of 25 out of 32). “It’s very close to the human ability to recognize identical twins,” says Dr. Esteller. Moreover, a correlation was found in 16 of the 32 pairs of the three programs, and these pairs formed the basis of further research.

Genome-wide analyzes for common genetic variations and their epigenetic profiles (genome regulatory mechanisms) were performed on salivary DNA samples, along with microbiome analysis. Genetic analysis revealed that nine of the 16 pairs had many common single nucleotide polymorphisms (SNPs), the most common type of genetic variation in humans. Among these 16 pairs, many had similar weights, and analysis of their biometric and lifestyle factors also showed that there were similarities. Behavioral traits such as smoking and educational level were correlated in similar pairs, suggesting that shared genetic variation is related not only to physical appearance, but may also influence common habits and behavior.

“Our findings provide a molecular basis for future applications in areas such as biomedicine, evolution and forensics. It would be very interesting to follow the potential application in forensic medicine, using the genome of unknown people to prepare bioinformatics strategies to reconstruct the face from DNA. And in medicine, we may be able to infer a person’s genome from facial analysis and therefore use it as a screening tool to detect the presence of disease-associated genetic mutations and apply preventative strategies to a early stage,” says Dr. Esteller.

“Some previous studies have compared the genome of individuals with facial features, but in the general population. Our study shows genetic markers essential to the development of the shape of the nose, lips and mouth, as well as completely new determinants of bone structure and skin texture that also provide characteristic features of our face. Environmental markers, such as epigenome and microbiome, were more distinct between lookalikes and therefore differences between these look-alikes can be attributed to chemicals that regulate the same DNA sequence and microbiome composition.

Although the study is small, it has the right statistical power, say the authors, who do not expect their results to change in a larger group. “Because the human population is now 7.9 billion, these similar repeats are increasingly likely to 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,” Dr. Esteller concludes.

*Look-alike humans identified by facial recognition algorithms show genetic similarities. Cell reports2022

Joshi RS, Rigau M, Garcia-Prieto CA, Castro de Moura M, Piñeyro D, Moran S, Davalos V, Carrión P, Ferrando-Bernal M, Olalde I, Lalueza-Fox C, Navarro A, Fernández-Tena C, Aspandi D, Sukno FM, Binefa X, Valencia A, Estelle M

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