Unique human faces evolved via social interactions

Why do humans have such an amazing variety of faces? To look unique and be easily recognisable and the highly visual social interactions throughout the history are the driver of this evolutionary trend.

"Clearly, we recognise people by many traits - for example their height or their gait - but our findings argue that the face is the predominant way we recognise people," said behavioural ecologist Michael J. Sheehan from the University of California (UC), Berkeley's Museum of Vertebrate Zoology.

Humans are phenomenally good at recognising faces and there is a part of the brain specialised for that.

"Our study now shows that humans have been selected to be unique and easily recognisable. It is clearly beneficial for me to recognise others but also beneficial for me to be recognisable. Otherwise, we would all look more similar," Sheehan added.

Sheehan and colleagues assessed human facial variability thanks to a US Army database of body measurements compiled from male and female personnel in 1988.

During the study, researchers found that facial traits are much more variable than other bodily traits - such as the length of the hand - and that facial traits are independent of other facial traits unlike most body measures.

The findings suggest that facial variation has been enhanced through evolution.

"The idea that social interaction may have facilitated or led to selection for us to be individually recognisable implies that human social structure has driven the evolution of how we look," noted Michael Nachman, a population geneticist at UC Berkeley.

The team also compared the genomes of people from around the world and found more genetic variation in the genomic regions that control facial characteristics than in other areas of the genome - a sign that variation is evolutionarily advantageous.

"Facial traits are more variable and less correlated than other traits and the genes that underlie them show higher levels of variation," Nachman maintained.

Researchers also found that facial variation in modern humans must have originated prior to the split between Neanderthals and Denisovans.

The study appeared in the online journal Nature Communications.