'Men are biologically more disposable than women'

The research by Professor Tom Kirkwood of the University of Newcastle suggested that the female body is better at carrying out routine maintenance and keeping the body's cells alive.

However, men are more disposable than women as the cells of their bodies are not genetically programmed to last as long as they are in females, said Professor Kirkwood. Scientists believe that the ageing process is caused by tiny faults throughout our body. As the tiny faults build up the length of our lives is determined 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, the Daily Mail reported. Professor Kirkwood's theory behind why our cells do not mend every tiny problem in our body is that it is built into our DNA.

The reason we do not live forever is because it would have cost our hunter-gather ancestors too much energy to constantly replenish cells when hunger was a more immediate danger, he said.

"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 wrote in 'American Scientist'.

"Our genes treated the body as a short-term vehicle, to be maintained well enough to grow and reproduce, but not worth a greater investment in durability when the chance of dying an accidental death was so great."

Previous studies have suggested that on average women live five to seven years longer than men. Genetic differences in their body and mensuration are said to be the key factors that help increase their longevity.

Scientists have also suggested that the fact a man's working life was more demanding could have accounted for their shorter lives. The new research by Professor Kirkwood also showed that females in most animal species live longer than males.

Professor Kirkwood said: "In females, reproductive success is so inextricably bound up with the integrity of the body and the evidence is really clear right across the life course -- men have a statistically significant, higher likelihood of dying at all ages compared to women.

"It seems to be deeply engrained in the biology.Obviously differences in lifestyle may add or subtract to it, but I'm absolutely convinced that there's an underlying biological explanation for the gender differences we see between the life expectancy of the sexes."