It is the ultimate battle of the sexes - and women usually win.

这是两性之间的终极较量——而且通常女性获胜。

Now scientists have come up with（提出，想出） a new theory for why woman live, on average, longer than men: men are more biologically ‘disposable’.

The controversial theory, developed by Professor Tom Kirkwood of the University of Newcastle, suggests that the female body is better at carrying out routine maintenance（日常维修） and keeping the body’s cells alive.

Professor Kirkwood believes there is now growing evidence to suggest that men are more disposable than women, because the cells of their bodies are not genetically¹ programmed to last as long as they are in females.

Many scientists believe that the aging process is caused by tiny faults throughout our body. As the tiny faults build up the length of our lives is determined² by how quickly our body is able to carry out running repairs.

As the cells miss opportunities to repair themselves our body gradually degrades until we eventually die.

Professor Kirkwood’s theory behind why our cells do not mend every tiny problem in our body is that it is built into our DNA³. The reason we do not live forever is because it would have cost our hunter-gather ancestors too much energy to constantly replenish⁴（补充） cells when hunger was a more immediate⁵ danger, he says.

‘Under the pressure of natural selection to make the best use of scarce energy supplies, our species gave higher priority to growing and reproducing than to living forever,’ he writes in the magazine American Scientist.

'In humans, as in most animal species, the state of the female body is very important for the success of reproduction', he writes.

‘The foetus（胎儿） needs to grow inside the mother’s womb, and the infant needs to suckle（哺乳，吮吸） at her breast. So if the female animal’s body is too much weakened by damage, there is a real threat to her chances of making healthy offspring. The man’s reproductive role, on the other hand, is less directly dependent on his continued good health.’