Facial facts: we have evolved to communicate

The need to develop social skills has helped shape the modern human face, suggested scientists.

Write in the newspaper Nature Ecology and Evolution, an international team proposes that our faces have evolved not only because of factors such as diet and climate, but also to offer more opportunities for gestural and nonverbal communication.

"We can now use our faces to signal more than 20 different categories of emotions via muscle contraction or relaxation," said Paul O. Higgins, of the University of York in the UK .

"It is unlikely that our early human ancestors had the same facial dexterity as the general shape of the face and that the positions of the muscles were different."

The researchers traced the evolution of the face since early African hominins until the appearance of modern human anatomy and concluded that they resulted from a combination biomechanical, physiological and social influences.

The human faces are thinner than those of other hominins and they have a smoother forehead with more visible and hairy eyebrows capable of greater freedom of movement. This allows us to express a wide range of subtle emotions, including recognition and sympathy.

And the changes did not stop.

The human face has been shaped in part by the mechanical demands of food and, over the last 100,000 years, their size has been shrinking as our growing ability to cook and process food reduced the need to chew, the researchers said.

This process of facial contraction has become particularly marked since the agricultural revolution: we went from hunter-gatherers to farmers, then to life in the city – lifestyles that led to increasingly processed foods and an effort less physical.

"Softer modern diets and industrialized societies can mean that the human face continues to shrink," said O. Higgins. "There are limits to what the human face can change … for example, breathing requires a sufficiently large nasal cavity.

"However, within these limits, the evolution of the human face should continue as long as our species survives, migrates and meets new environmental, social and cultural conditions."