Hands evolved not only for manual dexterity needed to use tools or create art but also so people could make fists and fight, University of Utah researchers say.

Humans have shorter palms and fingers than apes and longer, stronger, more flexible thumbs -- features long thought to have evolved to give humans the manual dexterity to make and use tools -- but "the proportions of our hands also allow us to make a fist," protecting delicate hand bones, muscles and ligaments during hand-to-hand combat, Utah biology Professor David Carrier said.

As 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 said in a university release Wednesday.

No ape hits with a clenched fist, the researchers said. Apes' elongated fingers and hands evolved so they could climb trees.

The human hand has apparently evolved for widely divergent uses, they said.

"It is arguably our most important anatomical weapon, used to threaten, beat and sometimes kill to resolve conflict," Carrier and study co-author Michael H. Morgan said in the Journal of Experimental Biology. "Yet it is also the part of our musculoskeletal system that crafts and uses delicate tools, plays musical instruments, produces art, conveys complex intentions and emotions, and nurtures.

"More than any other part of our anatomy, the hand represents the identity of Homo sapiens," they said. "Ultimately, the evolutionary significance of the human hand may lie in its remarkable ability to serve two seemingly incompatible but intrinsically human functions."