Human Hands Evolved for Punching: Scientists Slap Stuff with Cadavar Arms

First Posted: Oct 22, 2015 07:13 AM EDT

It may seem like a strange experiment, but it's telling researchers more about human evolution. Scientists have used cadaver arms to punch and slap padded dumbbells in order to see whether our hands evolved for fighting.

"The idea that aggressive behavior played a role in the evolution of the human hand is controversial," said David Carrier, senior author of the new study, in a news release. "Many skeptics suggest that the human fist is simply a coincidence of natural selection for improved manual dexterity. That may be true, but if it is a coincidence, it is unfortunate. As an alternative, we suggest that the hand proportions that allow the formation of a fist may tell us something about our evolutionary history and who we are as a species."

Humans have shorter palms and fingers and longer, stronger, flexible thumbs compared with other ape. These features have long been thought to have evolved so our ancestors had the manual dexterity to make and use tools.

In order to see whether our hands also evolved for fighting, researchers turned to cadaver arms. After hundreds of punches and slaps using eight arms, the researchers found that humans can safely strike with 55 percent more force with a fully buttressed fist than with an unbuttressed fist, and with twofold more force with a buttressed fist than with an open hand slap. It could be that these proportions improved manual dexterity while at the same time making it possible for the hand to be used as a club during fighting.

The findings reveal that our hands didn't just evolve for dexterity. It's very possible that they also evolved for attack and defense purposes.

The findings are published in the Journal of Experimental Biology.

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TagsEvolution, Human, Humans, human ancestor, Hands, Fight, Fighting, Fights