Human hands can be used to write, carry a tool, greet someone and punch someone else.

While scientists continue to disagree on which action drove the hand to evolve, David Carrier, professor of biology, believes it was the latter of the four.

In research published last week, Carrier, with graduate student Joshua Horns, tested the force of three different hand positions when hitting a weight. They observed how much strain was put on the bones, proving that a full fist is better at protecting the hand when in combat.

“We tried not to do a whole lot of speculation, but to show a pattern,” Horns said. “It gives us an idea of who we are as a creature.”

Using cadaver arms, Horns removed the skin and attached fishing lines to different muscle groups in the arms. Guitar tuners were adjusted to change the tension of the hand and position it as an unclenched fist, a fully clenched fist and an open-palmed slap. The hands swung into a dumbbell and they measured the impact the force had on the bones.

Carrier’s ideas about aggression being a driving factor in evolution have faced much persecution from the scientific community. His idea to test the human hand came when a friend confronted him about a paper proving sperm whales have big foreheads to ram each other. The friend raised a fist and said, “I can hit you in the face with this, but that’s not why it evolved.”

The desire to prove his friend wrong prompted Carrier to start his current research.

Carrier’s observations on aggression and its connection to the form also include robust faces to withstand blows and bipedal posture (standing on two feet) for a better combat stance.

“In every case, there’s been a loud chorus of people arguing that it’s silly,” Carrier said. Yet, there are some that stand by his theory so he continues to research and publish.

Looking to our past, Carrier said aggression was very important for our non-human and human primate ancestors. When we study the human brain, aggression is a natural response. Carrier and Horns think understanding why we evolved can help us better understand ourselves.

“Everyone would agree that violent tendencies are a big problem for our societies,” Horns said. “Unless we understand where we came from as a people and our evolution, it’s going to be a much more difficult problem to address.”

Most anthropologists look at the muscular thumbs and long fingers of a human hand and say they evolved for better manual dexterity. To them, the ability to make a fist is secondary.

“But, if it were all about manual dexterity, there would not be any differences,” Horns said. “There is consistent and well-recorded differences between men and women.”

Males are historically more aggressive, so Carrier’s research team will continue to study the hand by testing female and male hands for combative positions.

Although he has never been funded for this research and continues to face opposition, Carrier believes understanding our nature can only improve our species.

“We could be more aware of things that could lead to conflict and aggression and avoid them,” Carrier said. “We could see them coming, and stop them from happening.”

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