Humans who look alike act the same

A new study by Spanish researchers shows that human ‘look-alikes’ who have similar facial features also tend to share many genetic similarities, as well as certain lifestyle attributes.

The research, published in the journal Cell reports, provides insight into the molecular genetic mechanisms that contribute to facial construction. The authors say these findings could eventually be applied to forensics, enabling predictions of facial structure from DNA.

The experience

Ricky Joshi of the Josep Carreras Leukemia Research Institute in Barcelona and his colleagues collected portraits of 32 pairs of unrelated lookalikes from the photographs of Canadian artist Francois Brunelle, who has been collecting lookalike photographs since 1999.

Joshi and his colleagues used three different facial recognition algorithms to analyze the photographs to determine similarities between each pair. Twenty-five of the pairs were classified as “very similar” by at least two of the algorithms, and half were matched by all three, with scores comparable to identical twins. They then contacted everyone in the photographs they had chosen and asked them to complete a lifestyle questionnaire and submit a saliva sample.

The researchers extracted DNA from saliva samples and analyzed it in three different ways: They (1) compared each participant’s genome by mapping more than 4.3 million genetic variants called single nucleotide polymorphisms (SNPs) ; (2) examined participants’ “epigenomes” by comparing more than 850,000 DNA modification sites; and (3) used RNA sequencing to compare participants’ microbiomes.

Look alike, act alike

Analyzes revealed that 9 of 16 highly similar pairs shared more than 19,200 SNPs in more than 3,700 genes, and that these similarities were not due to shared ancestry. In contrast, there was very little similarity in their epigenomes and microbiomes. Moreover, these “ultra look-alikes” also shared physical characteristics such as weight and height, as well as habits and behaviors such as smoking and education level, suggesting that the shared genetic variants not only influence the physical appearance but also lifestyle.

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The study is limited by the small sample size, which is also not representative of the global population. Thirteen of the look-alike pairs were of European descent, and the other three were of Asian, South Asian, and Hispanic descent. Yet, it proves that those who look alike also act alike.

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