Socializing drove the evolution of the modern human face

April 15 (UPI) -- Why does the human face look the way it does? According to one group of researchers, it was the modern human's need to socialize that shaped the facial proportions and contours of Homo sapiens.

Early human ancestors were capable of relatively sophisticated tool usage, and Neanderthals made cave art. So what set modern humans apart? Some suggest it was a predilection for communication -- a predilection that encouraged cooperation and ultimately language.

In a new paper published in the journal Nature Ecology and Evolution, researchers argue it was the modern human's need to communicate that made Homo sapiens not just act different than their closest relatives, but also look different.

The modern human face, authors of the new paper claim, evolved to facilitate communication.

"We can now use our faces to signal more than 20 different categories of emotion via the contraction or relaxation of muscles," Paul O'Higgins, professor of anatomy at the Hull York Medical School, said in a news release. "It's unlikely that our early human ancestors had the same facial dexterity as the overall shape of the face and the positions of the muscles were different."

Unlike the large, sharp brow of Neanderthals, modern humans evolved a smooth forehead and more distinct eyebrows, both capable of a greater range of motion. Modern human faces also became more slender, allowing more subtle expressions of emotion.

Previous studies have highlighted the mechanics of eating as a driver of the evolution of the human face, while some researchers contend the modern human's violent tendencies influenced human heels and the shape of human fists.

The latest study suggests these research efforts have ignored the importance of socializing.

"We know that other factors such as diet, respiratory physiology and climate have contributed to the shape of the modern human face, but to interpret its evolution solely in terms of these factors would be an oversimplification," said O'Higgins.

According to O'Higgins, the demands of eating and breathing have placed limits on the physical parameters of human face evolution.

"However, within these limits, the evolution of the human face is likely to continue as long as our species survives, migrates and encounters new environmental, social and cultural conditions," he said.