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"Because you have higher pressure when hitting with a fist, you are more likely to cause injury" to tissue, bones, teeth, eyes and the jaw, Carrier says. So the peak stress delivered to the punching bag – the force per area – was 1.7 to three times greater with a fist strike compared with a slap. However, a fist delivers the same force with one-third of the surface area as the palm and fingers, and 60 percent of the surface area of the palm alone. To the researchers' surprise, the peak force was the same, whether the bag was punched with a fist or slapped with an open hand. The bag was instrumented to allow calculation of the force of the punches and slaps.
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So, Carrier and Morgan had 10 male students and nonstudents – ages 22 to 50 and all of them with boxing or martial arts experience – hit a punching bag as hard as they could.Įach subject delivered 18 hits, or three of each for six kinds of hits: overhead hammer fists and slaps, side punches and slaps, and forward punches and palm shoves. The first experiment tested the hypothesis that humans can hit harder with a fist. Photo Credit: Denise Morgan for the University of Utah
#Difference between human and chimpanzee hand manual
A new University of Utah study argues that human hands evolved not only for manual dexterity, but for fighting. That not only allows fine manipulation of tools and other objects, but allows humans to make a clenched fist, which apes cannot. Morgan – a University of Utah medical student – conducted their study to identify any performance advantages a human fist may provide during fighting.Ĭompared with a chimpanzee hand, at left, the human hand, at right, has shorter fingers and palms and a longer, stronger more flexible thumb. So Carrier and study co-author Michael H. "If a fist posture does provide a performance advantage for punching, the proportions of our hands also may have evolved in response to selection for fighting ability, in addition to selection for dexterity," Carrier says. Fights also were for food, water, land and shelter to support a family, and "over pride, reputation and for revenge," he adds. If we can understand what our anatomy has evolved to do, we'll have a clearer picture of who we were in the beginning, and whether aggression is part of who we are."Ĭarrier agrees that human hands evolved for improved manual dexterity, but adds that "the proportions of our hands also allow us to make a fist," protecting delicate hand bones, muscles and ligaments during hand-to-hand combat.Īs our ancestors evolved, "an individual who could strike with a clenched fist could hit harder without injuring themselves, so they were better able to fight for mates and thus more likely to reproduce," he says. "Our anatomy holds clues to that question. Humans have debated for centuries "about whether we are, by nature, aggressive animals," he adds. "We're the poster children for violence."
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"There are people who do not like this idea, but it is clear that compared with other mammals, great apes are a relatively aggressive group, with lots of fighting and violence, and that includes us," Carrier says. 19 by the Journal of Experimental Biology. "The role aggression has played in our evolution has not been adequately appreciated," says University of Utah biology Professor David Carrier, senior author of the study, scheduled for publication Dec. Compared with apes, humans have shorter palms and fingers and longer, stronger, flexible thumbs – features that have been long thought to have evolved so our ancestors had the manual dexterity to make and use tools.