Not surprisingly, your looks are largely hereditary. But exactly which genes are responsible for which externally visible characteristics remains largely unknown. New research from Erasmus MC partially fills that knowledge gap.
A large study of nearly 10,000 people of European descent revealed 3 new genes that determine how thick the eyebrows are. The scientists also rediscovered some genes already known to be associated with eyebrow thickness in people of Latin American and Chinese descent.
‘So, the same appearance trait in people of different ancestry partly has the same and partly a different genetic basis,’ said Prof. Manfred Kayser, head of the Department of Genetic Identification at Erasmus MC. He led the study conducted by the International Visible Trait Genetics Consortium. The results were published in the Journal of Investigative Dermatology.
Ears
In the second study, Kayser and colleagues show that 16 genes are associated with how the ears look. Of those 16 genes, 8 are newly discovered. The scientists used artificial intelligence to analyze photographs of the ears of nearly 15,000 people of European, Asian, and Latin American descent. They identified 136 characteristics that describe what an ear looks like. Using these characteristics and the C-GWAS statistical-genetic analysis technique developed by Kayser and his team, the genes that determine the shape of ears emerged. The study was published in PLOS Genetics.
‘We can already predict eye color, skin color, and hair color from a crime scene trace’
Eventually, this genetic knowledge is going to find its way into forensic investigations, Kayser envisions. Predicting appearance from crime scene DNA can help the police to find unknown perpetrators in cases where there is DNA but no match with the forensic DNA database. ‘Thanks to our previous work, we can already predict eye color, skin color, and hair color from a crime scene trace. Recently, we developed a combined DNA test for seven external characteristics: eye color, skin color, hair color, eyebrow color, freckles, hair shape, and male hair loss,’ Kayser said. He did so in the VISAGE Consortium he coordinated.
Cold cases
Based on the two new studies, it is not yet possible to predict the shape of ears and eyebrow thickness from DNA. Kayser: ‘The genes we found have too small effects. The difference with eye color, for example, is there are a few genes with larger effects. For externally visible characteristics that have nothing to do with color, such as ear shape, eyebrow thickness, or the whole face, there are no genes with large effects but only those with small effects. So, we need to find many more genes to be able to predict these characteristics from DNA as well. That is not easy, mostly because there is insufficient funding for this type of research.’
In the Netherlands alone, there are hundreds of cold cases where there is DNA but no DNA match. Kayser and his team therefore want to do more research into the genetics of appearance. ‘We are doing this research because we want to understand why people look the way they do and to understand the relationship between appearance and certain diseases. But also because we want to put the police on the trail of an unknown perpetrator. Preferably with a long list of DNA predicted externally visible characteristics: the longer the list, the better the focused police investigation works.’
