It is said that one cannot judge a book by its cover. Yet when it comes to faces, it turns out that similar features are more than just skin deep.
Doppelgangers do not just look alike, they are alike, scientists have found, after carrying out an in-depth study of the genetics and behaviour of unrelated people who share uncanny facial similarities. Researchers recruited 16 pairs of doubles from the photographic work of François Brunelle, a Canadian artist who has been collecting pictures of unrelated lookalikes since 1999.
Participants were given a detailed questionnaire asking about factors from education and smoking habits to height, weight, exercise, coffee intake, alcohol consumption, marriage status, employment and even whether they owned pets.
These results showed there was a strong correlation between people who looked alike and their lifestyles and behavioural traits. And when they checked their genetic profiles, the team also found that people who looked alike had similar DNA.
Pairs were found to share 20,000 genetic variants between them, relating to shape and features of mouth, lips, eyes, eyebrows, nose, skull and bone structure, skin textures, body fat and liquid retention and even personality characteristics, such as tobacco addiction.
“Our study provides a rare insight into human likeness by showing that people with extreme lookalike faces share common genotypes," said senior author Manel Esteller, of the Josep Carreras Leukaemia Research Institute in Barcelona, Spain.
Taken together, the results suggest that shared genetic variation not only relates to similar physical appearance but may also influence common habits and behaviour.
The team believes the findings could be important for forensic research, such as for determining facial shape or behaviour based on DNA.
“We provided a unique insight into the molecular characteristics that potentially influence the construction of the human face,” added Dr Esteller.
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