June 9, 2014
Evolution Played A Role In Getting The Male Face Ready For Violence
Brett Smith for redOrbit.com - Your Universe Online
Throughout history, men have had a well-earned reputation for violence and a new study in the journal Biological Reviews has concluded that masculine facial features evolved as a result of that violence.
"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," said study author David Carrier, a biologist at the University of Utah. "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."
The Utah biologist said his team’s report considered numerous factors and aspects of early hominids.
"When modern humans fight hand-to-hand the face is usually the primary target,” Carrier said. “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.”
For example, the jaws of these early hominids slowly became more robust and able to withstand a significant blow.
"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," Carrier told BBC News. "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."
“These bones are also the parts of the skull that show the greatest difference between males and females in both australopiths and humans,” he added. “In other words, male and female faces are different because the parts of the skull that break in fights are bigger in males.”
The study team noted that descendants of the australopiths, including humans, have displayed less and less facial buttressing against violence.
"Our arms and upper body are not nearly as strong as they were in the australopiths," Carrier explained. "There's a temporal correlation."
This latest study builds on previous research from Carrier that concluded early hominids were the first animals to evolve hands capable of making a punch-throwing fist. That conclusion received a fair share of criticism and the newest work supports that earlier controversial conclusion, Carrier said.
"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; that civilization actually corrupted humans and made us more violent,” the Utah biologist said. “This idea remains strong in the social sciences and in recent decades has been supported by a handful of outspoken evolutionary biologists and anthropologists. Many other evolutionary biologists, however, find evidence that our distant past was not peaceful.”
"(Our paper) does address this debate of whether our past was violent or peaceful," he told the BBC. "That's an argument that's been going on for a very long time."
"The historical record goes back a short time, the archaeological record goes back a few tens of thousand years more,” he continued. “But the anatomy holds clues to what selection was important, what behaviors were important, and so it gives us information about the very distant past."
Image 2 (below): University of Utah biologist David Carrier and Michael H. Morgan, a University of Utah physician, contend that human faces -- especially those of our australopith ancestors -- evolved to minimize injury from punches to the face during fights between males. Their research is published in the June 9 issue of Biological Reviews. Credit: Courtesy image/University of Utah