What’s in a smile? Humans faces evolved as our ancestors ‘self-domesticated’ by choosing friendlier, less aggressive mates – which showed in our facial expressions

  • Scientists at the University of Milan investigated the history of facial expressions
  • They found a series of mutations in a gene associated with friendly facial expressions
  • The mutations weren’t present in genetic samples from Neanderthals 
  • They suggest these mutations could have cause humans to self-select less aggressive mating partners and ‘self-domesticate’ themselves

A new study suggest that ability to convey kindness through facial expressions may have been a key factor in human evolution.

The study was conducted by Matteo Zanella and a team of researchers at the University of Milan, and published this week in Science Advances.

The team compared genetic data from human stem cells with samples from the remains of two Neanderthals and one Denisovan, a sister species to Neanderthals found in central Asia.

A new study from the University of Milan suggests the ability to convey friendly and welcoming facial expressions was one of the keys to human evolution

A new study from the University of Milan suggests the ability to convey friendly and welcoming facial expressions was one of the keys to human evolution

They specifically focused on the BAZ1B gene, which has been connected to Williams-Beuren syndrome, a condition that causes people to develop wide mouths and small noses that give a generally kind and welcoming impression.

The BAZ1B gene has also been associated with the evolution of two extra muscles in dogs that allow them to widen and narrow their eyes in expressive ways, something wolves aren’t able to do.

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Researchers found a number of mutations in the BAZ1B gene in the contemporary stem cell samples, which led them to believe the gene is a ‘master regulator’ that influences human facial expressions.

They suggest that these mutations in the BAZ1B gene, which were absent in the Neanderthal and Denisovan samples, likely helped humans evolve by encouraging people to choose mates who conveyed kind or friendly facial expressions.

The researchers suggest that Neanderthals (pictured above) lacked a series of mutations in the BAZ1B gene that's linked to the parts of the brain that control facial expression

The researchers suggest that Neanderthals (pictured above) lacked a series of mutations in the BAZ1B gene that’s linked to the parts of the brain that control facial expression

Selective mating practices among the small number of Neanderthals that did develop some of the BAZ1B gene mutations could have contributed to the eventual evolution of homo sapiens with their distinctively expressive faces

Selective mating practices among the small number of Neanderthals that did develop some of the BAZ1B gene mutations could have contributed to the eventual evolution of homo sapiens with their distinctively expressive faces

‘We suspect the facial changes were part of a process of reduction in reactive aggression, boosting our pro=social, cooperative profile,’ Zanella told Newsweek.

The researchers say their findings are the ‘first empirical validation of the self-domestication hypothesis.’ 

Self-domestication is a term used to describe reproductive behaviors in wild animals that led to evolutionary shifts without human intervening to force selective breeding practices.

Scientists describe mating behaviors not imposed through any external force as 'self-domestication,' something that contributed to the domestication of dogs, cats, and even bonobos

Scientists describe mating behaviors not imposed through any external force as ‘self-domestication,’ something that contributed to the domestication of dogs, cats, and even bonobos

‘It is all too easy to view human evolution as about individualistic success, but these findings illustrate another example of how interpersonal social processes were critical in what made us human,’ University of York lecturer Penny Spikins told Newsweek.

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Spikins didn’t work directly on the study but says it’s an important step in clarifying the relationship between the evolution of the human brain and the evolution of the species, something that shows ‘how important emotional and social sensitivity is to what makes us human.’

A TIMELINE OF HUMAN EVOLUTION

The timeline of human evolution can be traced back millions of years. Experts estimate that the family tree goes as such:

55 million years ago – First primitive primates evolve

15 million years ago – Hominidae (great apes) evolve from the ancestors of the gibbon

7 million years ago – First gorillas evolve. Later, chimp and human lineages diverge

A recreation of a Neanderthal man is pictured 

A recreation of a Neanderthal man is pictured 

5.5 million years ago – Ardipithecus, early ‘proto-human’ shares traits with chimps and gorillas

4 million years ago – Ape like early humans, the Australopithecines appeared. They had brains no larger than a chimpanzee’s but other more human like features 

3.9-2.9 million years ago – Australoipithecus afarensis lived in Africa.  

2.7 million years ago – Paranthropus, lived in woods and had massive jaws for chewing  

2.6 million years ago – Hand axes become the first major technological innovation 

2.3 million years ago – Homo habilis first thought to have appeared in Africa

1.85 million years ago – First ‘modern’ hand emerges 

1.8 million years ago – Homo ergaster begins to appear in fossil record 

800,000 years ago – Early humans control fire and create hearths. Brain size increases rapidly

400,000 years ago – Neanderthals first begin to appear and spread across Europe and Asia

300,000 to 200,000 years ago – Homo sapiens – modern humans – appear in Africa

50,000 to 40,000 years ago – Modern humans reach Europe

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