Taking It on the Chin

Humans have evolved to make tools, tell stories, and—at least according to some U studies—to fight. For years, David Carrier, U professor of biology, has been exploring the hypothesis that generations of male-male aggression long in the past shaped the musculoskeletal system of human bodies. Previous work has shown that the proportions of the hand aren’t just for manual dexterity—they also protect the hand when it’s formed into a fist. Other studies have looked at the strength of the bones of the face and how our heels, planted on the ground, can confer additional upper-body power.

“In mammals in general,” notes Carrier, “the difference between males and females is often greatest in the structures that are used as weapons.”

One study found that males’ average power during a punching motion was 162 percent greater than that of females, with the least powerful man still stronger than the most powerful woman. Such a distinction between genders, Carrier says, develops with time and with purpose.

The evolutionary battlefield of our past provided the perfect foundation for one U student’s further research—into the cushioning effects of beards. Ethan Beseris HBS’18, while an undergraduate, joined Carrier and Steven Naleway, associate professor of mechanical engineering, in a study that earned an Ig Nobel Prize in 2021. The lighthearted award is intended to celebrate science that first makes people laugh, and then makes them think.

The team used sheep fleece to model human hair and epoxy composite to model facial bones, then utilized a drop weight impact tester to measure impact force and energy absorbed. They determined that “fully furred samples” could absorb more energy than samples that had been plucked or sheared. The findings were published in the journal Integrative Organismal Biology in 2020.

It’s an uncomfortable thought to consider that men may be optimized for fighting, says Carrier. But it doesn’t mean that men today are destined to live their ancestors’ violent lives. “Human nature is also characterized by avoiding violence and finding ways to be cooperative and work together, to have empathy, and to care for each other,” he adds.