Human Hand Evolved Into Fist for Punching and Fighting, Says New Study

Scientists at the University of Utah believe they may have figured out why the human hand has such a unique shape in the animal kingdom: it's very good for throwing punches.

Humans have shorter fingers and much stronger and more advanced thumbs, which makes us very good at manual dexterity and manipulating small and complex objects.

But it also makes an excellent fist. The large thumb wraps around the short fingers, protecting them from impact during a fight and concentrating the force of the blow to cause more damage to the target.

Scientists measured the force generated by boxers and martial artists when they threw punches either normally or with an open-handed slap.

In both instances, the fighters generated the same amount of force with their punch, no matter the shape of their hand, but the fist spread that force out over a much smaller surface area-ideal for a weapon.

Many animals have natural weapons, like horns and fangs, and some are even good at crushing with blunt appendages. An elephant's foot isn't very sharp, but it can smash a human head easily.

And some animals are capable of fine motor coordination. Chimpanzees and apes use their fingers to manipulate tools, and gorilla can even speak sign language.

But few shapes, and perhaps no others that have evolved in the animal kingdom, are good at both delicate movement and killing.

"The structure of the human fist provides buttressing that increases the stiffness of the second MCP joint by fourfold and, as a result of force transfer through the thenar eminence, more than doubles the ability of the proximal phalanges to transmit  ʻpunchingʼ force," said the article by Michael H. Morgan and David R. Carrier in The Journal of Experimental Biology.

"Thus, the proportions of the human hand provide a performance advantage when striking with a fist. We propose that the derived proportions of hominin hands reflect, in part, sexual selection to improve fighting performance."