Men's faces may look different from women's because they evolved to withstand punches, according to a new study from the University of Utah.
Fistfights over women or resources and other disagreements caused male faces to become thicker in certain areas, according to a study published Monday. The areas of the skull that are most likely to be fractured during a fight had the greatest increase in robusticity during the evolution of basal hominins, an ancestor of humans, said lead author David Carrier.
"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," Carrier said in a statement. "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."
Previously, researchers have theorized that the human face evolved to be more robust to allow for chewing hard foods like nuts. Instead, Carrier said his research suggests that violence played a greater role in evolution.
The face is the primary target in fighting, so Carrier said it would make sense for the face to evolve to better protect itself from injury.
"These bones are also the parts of the skull that show the greatest difference between males and females in both australopiths and humans," Carrier said. "In other words, male and female faces are different because the parts of the skull that break in fights are bigger in males."
The role violence played in evolution has long been debated.
"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. This idea remains strong in the social sciences," Carrier said. "Many other evolutionary biologists, however, find evidence that our distant past was not peaceful."
The study was published in the journal "Biological Reviews."