From the field of evolutionary biology comes a new study suggesting that the shape of our face is a result of violence in our prehistoric ancestors. Researchers from the latest study, published in Biological Reviews, say human faces evolved to minimize the impact of injury from punches to the face among males.
The team, led by biologist David Carrier and physician Michael H. Morgan of the University of Utah, focused on our australopith ancestors. These are human-like primates that lived in Africa between 6 and 1.2 million years ago.
Australopiths had a mix of both human and ape traits, walked on two legs, had small brains, small canine teeth - like humans - but their cheek teeth were quite large.
The most widely known example of an australopith is "Lucy," a well-preserved fossilized skeleton from Ethiopa dated to around 3.2 million years ago.
Previously, the most prominent hypothesis held that the evolution of our ancestors' hefty faces was a result of the need to chew foods that were difficult to crush, such as nuts.
But Carrier says australopiths had traits that could have boosted fighting ability, such as hand proportions that allowed them to make a fist, which is effective for striking others. He adds:
"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."
He adds that he and his colleagues considered that when humans fight today with their hands, the face is typically the main 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," he says.
Fossil record coincides with theory
Carrier further explains that such bones are part of the skull that exhibits the biggest difference between both australopith and human men and women.
New research suggests human faces - particularly those of our australopith ancestors - evolved to minimize injury from punches to the face during fights between males.
Image credit: University of Utah
"In other words," he says, "male and female faces are different because the parts of the skull that break in fights are bigger in males."
But most importantly, he notes that such facial features are found in the fossil record around the same time our ancestors developed the hand proportions that allowed them to make a fist.
He adds that, 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."
The team notes that their study adds to the continuing conversation about the role violence played in our evolution, and they say their work suggests violence played a larger role in human evolution than many anthropologists generally accept.
"I think our science is sound," says Morgan, "and fills some longstanding gaps in the existing theories of why the musculoskeletal structures of our faces developed the way they did."
Such research into the evolution of the immediate predecessors of the human genus Homo is relevant, says the team, as it provides insight into how and why we evolved into what we are now from our ancestors who lived 4-5 million years ago.
Did civilization make us more violent?
Carrier says their new research not only provides a different reason for the evolution of our faces, but also "addresses the debate over whether or not our distant past was violent."
"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."
This debate about the dark side of human nature goes back to French philosopher Rousseau, notes Carrier, who says the philosopher "argued that before civilizations humans were noble savages; that civilization actually corrupted humans and made us more violent."
Carrier adds that this idea has remained strong in the social sciences.
In 2013, Medical News Today reported on a study published in The Lancet, which suggested heart disease among ancient mummies was more common than previously thought.