A new study has shown men hit hardest when striking downwards and the blows of a taller man are more powerful than the thumps of a short man. In evolutionary terms, that makes them more useful for women, says lead author Dr David Carrier.
He added: "From the perspective of sexual selection theory, women are attracted to powerful males, not because powerful males can beat them up, but because powerful males can protect them and their children from other males."
Earlier studies suggested that women prefer tall men because their height indicates they have "good genes".
But, Dr Carrier disagrees.
"If that were the whole story, I would expect the same to be true for men -- that men would be attracted to tall women. But they`re not. Men are attracted to women of average height or even shorter,"the `Daily Mail` quoted him as saying.
In their study, the researchers of Utah University found that our prehistoric ancestors punched hardest when they stood on two legs -- suggesting that fighting was the driving force behind the evolution of upright walking.
Dr Carrier said: "The results of this study are consistent with the hypothesis that our ancestors adopted bipedal posture so that males would be better at beating and killing each other when competing for females.
"Standing up on their hind legs allowed our ancestors to fight with the strength of their forelimbs, making punching much more dangerous. It also provides a functional explanation for why women find tall men attractive.
"Early in human evolution, an enhanced capacity to strike downward on an opponent may have given tall males a greater capacity to compete for mates and to defend their resources and offspring. If this were true, females who chose tall males would have had greater fitness for survival."
In their study, the researchers analysed the power of punches by male martial arts experts and boxers as they struck out in four directions - upwards, down, sideways and forwards.
Men hit with more force when they were standing -- and could punch twice as hard when they were striking downwards, according to the findings published in the latest edition of the `PLoS One` journal.