University of Utah researchers analyzed the forces and acceleration involved when different martial artists hit a punching bag. They found that the structure of the fist provides additional support for the knuckles to transmit punching force.

“We asked the question: ‘can you strike harder with a fist than with an open palm?’,” co-author David Carrier explained. “We were surprised because the fist strikes were not more forceful than the strikes with the palm. In terms of the work on the bag there is really no difference.”

Of course, there is a striking difference between the two techniques; while the force is the same, the surface on which is applied is much smaller in the case of a fist – so a punch does much more practical damage.

“The force per area is higher in a fist strike and that is what causes localised tissue damage,” said Prof Carrier. “There is a performance advantage in that regard. But the real focus of the study was whether the proportions of the human hand allow buttressing (support).”

Research didn’t thought this was an evolutionary coincidence, and indeed, they observed that a clenched fist provides much more support and protection for the hand’s delicate bones, something preventing you from doing more damage to yourself when punching. Clenching a fist increases the second meta-carpo-phalangeal joint (the visible knuckles when you clench your fist) stiffness by a factor of four.

Researchers note that the human hand is also shaped for an increased dexterity in handling a number of objects and tasks, so they presume that the hand evolved both for dexterity and punching force – two things which don’t exactly go hand in hand.

“There may, however, be only one set of skeletal proportions that allows the hand to function both as a mechanism for precise manipulation and as a club for striking,” the researchers write. “Ultimately, the evolutionary significance of the human hand may lie in its remarkable ability to serve two seemingly incompatible, but intrinsically human, functions.”

What’s interesting is that our closes relatives, chimpanzees, not only don’t clench fists – but are actually unable to do so. This seems to indicate, in the scientists’ interpretation, that humans are much more aggressive as a species than our closes relatievs – something which many believe is a key attribute that contributed to our rise as a dominant species.

“There may, however, be only one set of skeletal proportions that allows the hand to function both as a mechanism for precise manipulation and as a club for striking,” the researchers write. “Ultimately, the evolutionary significance of the human hand may lie in its remarkable ability to serve two seemingly incompatible, but intrinsically human, functions.”

The research was published in the Journal of Experimental Biology.