A new study suggests that human hands evolved so that men could form fists and fight.
Researchers at the University of Utah found that not only did hands develop for better manual dexterity but also to make war and defend ourselves.
Human palms are more compact than that of apes and human have longer thumbs that are more flexible, reported the Los Angeles Times.
To test their hypothesis, the researchers conducted three trials.
The first test saw participants who were trained in boxing or martial arts hit a punching bag to test the power of their blows.
They used both an open hand slap and a punch, the latter being 1.7 to three times more powerful.
The two other trials were designed to show how a fist guarded the delicate bones in the hand during combat.
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Watching how pressure moved through hand during a punch, they determined that the stiffness of the knuckle joint increased four times by clenched fists, said NBC News.
"The role aggression has played in our evolution has not been adequately appreciated," said study author David Carrier, reported Medical News Today.
"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. We're the poster children for violence."
Medical News Today pointed out that the real reason may never be fully understood but the fact that we no longer (regularly) climb trees may also have something to do with the size and shape of our hands.
The study was published in the Journal of Experimental Biology.