The evolution of faces has been enhanced by fighting which forced human faces to evolve to minimise injuries, a study has found.

According to the paper "Protective buttressing of the hominin face", published in Biological Reviews, human faces —especially those of our australopith ancestors — evolved to minimise injury from punches to the face during fights between males.

"The australopiths were characterised by a suite of traits that may have improved fighting ability, including hand proportions that allow formation of a fist; effectively turning the delicate musculoskeletal system of the hand into a club effective for striking," said biologist David Carrier, lead author of the study.

"If indeed the evolution of our hand proportions were associated with selection for fighting behaviour you might expect the primary target, the face, to have undergone evolution to better protect it from injury when punched.

"What we found was that the bones that suffer the highest rates of fracture in fights are the same parts of the skull that exhibited the greatest increase in robusticity during the evolution of basal hominins.

"These facial features appear in the fossil record at approximately the same time that our ancestors evolved hand proportions that allow the formation of a fist. Together these observations suggest that many of the facial features that characterise early hominins may have evolved to protect the face from injury during fighting with fists," Carrier continued.

The new findings represent an alternative explanation to the previous theory according to which human faces evolved as a result from the need of our ancestors to chew hard-to-crush foods such as nuts.

According to Carrier, the study also addresses the debate over the role of violence during evolution.

"The debate over whether or not there is a dark side to human nature goes back to the French philosopher Rousseau who argued that before civilisation humans were noble savages; that civilisation actually corrupted humans and made us more violent," said Carrier. "Many other evolutionary biologists, however, find evidence that our distant past was not peaceful."

Carrier is currently working on a study on foot posture of great apes that also relates to evolution and fighting ability.