Scientists Say Hominin Face Evolved to Minimize Injury From Punches

Posted on June 9, 2014

Researchers say in a new study that hominin faces, particular faces of our australopith ancestors, evolved to minimize injury from punches to the face. A stronger and differently shaped jaw could potentially absorb more punches without breaking. This is an alternative theory to the hypothesis that our ancestors' faces evolved from the new to chew hard-to-crush foods like nuts. This new punching defense theory is proposed by University of Utah biologist David Carrier and Michael H. Morgan, a University of Utah physician.

Carrier says in a statement, "The australopiths were characterized 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. 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."

A jaw shattering punch could have been deadly before there was easy access to physicians to repair a broken jaw. A broken jaw could have killed a hominid if it became unable to eat as a result.

Carrier told BBC News, "Jaws are one of the most frequent bones to break - and it's not the end of the world now, because we have surgeons, we have modern medicine. But four million years ago, if you broke your jaw, it was probably a fatal injury. You wouldn't be able to chew food... You'd just starve to death."

Carrier also says, "When modern humans fight hand-to-hand the face is usually the primary target. 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."

A research paper on the study was published in Biological Reviews.

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