A controversial new paper from the University of Utah contends that human faces have evolved over time to minimize injury from punches to the face during fights. The new theory, detailed in the journalBiological Reviews, presents an alternative view to the long-held hypothesis that the robustness of our faces resulted largely from the need to chew hard-to-crush foods.

The authors of the new paper, University of Utah scientists David Carrier and Michael H. Morgan, say that our Australopith ancestors were characterized by traits that would appear to have improved their 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. “If indeed the evolution of our hand proportions were associated with selection for fighting behavior you might expect the primary target, the face, to have undergone evolution to better protect it from injury when punched,” said Carrier, lead author of the study.

He adds that the rationale for the paper’s conclusions came from determining a number of different elements. “When modern humans fight hand-to-hand the face is usually the primary target,” he explained. “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 bones are also the parts of the skull that show the greatest difference between males and females in both Australopiths and humans. In other words, male and female faces are different because the parts of the skull that break in fights are bigger in males.”

“Importantly, 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 characterize early hominins may have evolved to protect the face from injury during fighting with fists,” he added.

The new paper by Carrier and Morgan builds on the pair’s previous work, which suggested that violence played a greater role in human evolution than is generally accepted by many anthropologists. Specifically, Carrier has previously investigated the short legs of great apes, the habitual bipedal posture of hominins, and the hand proportions of hominins.

Carrier said the new work “provides an alternative explanation for the evolution of the hominin face” but also “addresses the debate over whether or not our distant past was violent.”

“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 civilization humans were noble savages,” he explained. “The hypothesis that our early ancestors were aggressive could be falsified if we found that the anatomical characters that distinguish us from other primates did not improve fighting ability. What our research has been showing is that many of the anatomical characters of great apes and our ancestors, the early hominins [such as bipedal posture, the proportions of our hands and the shape of our faces] do, in fact, improve fighting performance.”

Morgan added that the new study brings interesting elements to the ongoing conversation about the role of violence in evolution. “I think our science is sound and fills some longstanding gaps in the existing theories of why the musculoskeletal structures of our faces developed the way they did,” he said.

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